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1.  Oxidized Calmodulin Kinase II Regulates Conduction Following Myocardial Infarction: A Computational Analysis 
PLoS Computational Biology  2009;5(12):e1000583.
Calmodulin kinase II (CaMKII) mediates critical signaling pathways responsible for divergent functions in the heart including calcium cycling, hypertrophy and apoptosis. Dysfunction in the CaMKII signaling pathway occurs in heart disease and is associated with increased susceptibility to life-threatening arrhythmia. Furthermore, CaMKII inhibition prevents cardiac arrhythmia and improves heart function following myocardial infarction. Recently, a novel mechanism for oxidative CaMKII activation was discovered in the heart. Here, we provide the first report of CaMKII oxidation state in a well-validated, large-animal model of heart disease. Specifically, we observe increased levels of oxidized CaMKII in the infarct border zone (BZ). These unexpected new data identify an alternative activation pathway for CaMKII in common cardiovascular disease. To study the role of oxidation-dependent CaMKII activation in creating a pro-arrhythmia substrate following myocardial infarction, we developed a new mathematical model of CaMKII activity including both oxidative and autophosphorylation activation pathways. Computer simulations using a multicellular mathematical model of the cardiac fiber demonstrate that enhanced CaMKII activity in the infarct BZ, due primarily to increased oxidation, is associated with reduced conduction velocity, increased effective refractory period, and increased susceptibility to formation of conduction block at the BZ margin, a prerequisite for reentry. Furthermore, our model predicts that CaMKII inhibition improves conduction and reduces refractoriness in the BZ, thereby reducing vulnerability to conduction block and reentry. These results identify a novel oxidation-dependent pathway for CaMKII activation in the infarct BZ that may be an effective therapeutic target for improving conduction and reducing heterogeneity in the infarcted heart.
Author Summary
Calmodulin kinase II (CaMKII) is a multifunctional serine/threonine kinase that regulates diverse functions in heart. Recently, a novel pathway for CaMKII activation was discovered where oxidation of the kinase at specific methionine residues produces persistent activity. This alternative oxidation-dependent pathway has important implications for heart disease where oxidative stress is increased (e.g., heart failure and following myocardial infarction). We hypothesized that myocardial infarction caused by occlusion of a coronary artery would increase levels of oxidized CaMKII. Moreover, we hypothesized that oxidative CaMKII activation represents an important mechanistic link between increased oxidative stress and life-threatening heart rhythm disturbances (arrhythmias) in heart disease. We report a dramatic increase in levels of oxidized CaMKII following myocardial infarction in the canine. Based on these experimental data, we developed a novel mathematical model of CaMKII activity to study the role of oxidation-dependent CaMKII activation in regulating cardiac cell excitability. Our findings identify a novel role for oxidation-dependent CaMKII activation following myocardial infarction and provide a mechanistic link between oxidative stress and lethal cardiac arrhythmias in heart disease.
PMCID: PMC2778128  PMID: 19997488
2.  Calcium entry mediates hyperglycemia-induced apoptosis through Ca2+/calmodulin-dependent kinase ll in retinal capillary endothelial cells 
Molecular Vision  2012;18:2371-2379.
Hyperglycemia-induced vascular cell apoptosis is a seminal early event in diabetic retinopathy. Prolonged hyperglycemia is known to increase intracellular cytosolic free calcium ([Ca2+]i) in retinal vascular endothelial cells (RECs), suggesting that [Ca2+]i is a critical trigger for microvascular degeneration. This study aims to elucidate Ca2+-dependent signaling mechanisms that mediate hyperglycemia-induced apoptosis in RECs.
A cultured macaque choroid-retinal endothelial cell line (RF/6A) was incubated in normal glucose (NG), NG plus the Ca2+ entry blocker 2-aminoethoxydiphenyl borate (2-APB), high glucose (HG), or HG plus either 2-APB, the c-jun N-terminal kinase (JNK) inhibitor SP600125, or the calcium/calmodulin-dependent protein kinase II (CaMKII) inhibitor KN93. Changes in [Ca2+]i evoked by adenosine 5′-triphosphate (ATP) were measured in fluo-3/AM-loaded RF/6A cells by confocal microscopy. The mitochondrial membrane potential (ΔΨm) and apoptosis were assessed by flow cytometry. Expression levels of CaMKII, phosphorylated CaMKII (p-CaMKII), c-Jun N-terminal kinase (JNK), phosphorylated JNK (p-JNK), the death receptor (Fas), and cytochrome c were detected by western blotting analysis.
Prolonged exposure to HG (96 h) potentiated ATP-evoked Ca2+ entry as well as CaMKII phosphorylation and RF/6A cell apoptosis. Enhanced apoptosis was blocked by 2-APB and KN93. Furthermore, HG increased JNK phosphorylation and Fas expression, and both responses were partially blocked by 2-APB and KN93, while the JNK inhibitor SP600125 partially reduced HG-induced Fas expression. In addition, HG depolarized the ΔΨm and triggered the release of mitochondrial cytochrome c. These early signs of mitochondria-dependent apoptosis were partially reversed by 2-APB and KN93.
HG-induced apoptosis in RF/6A cells depends on Ca2+ entry and CaMKII activation, leading to the activation of both Fas-dependent and mitochondria-dependent apoptosis pathways. The CaMKII−JNK−Fas pathway is involved in HG-evoked apoptosis of RECs.
PMCID: PMC3462598  PMID: 23049237
3.  CaMKII Negatively Regulates Calcineurin-NFAT Signaling in Cardiac Myocytes 
Circulation research  2009;105(4):316-325.
Pathologic cardiac myocyte hypertrophy is thought to be induced by the persistent increases in intracellular Ca2+ needed to maintain cardiac function when systolic wall stress is increased. Hypertrophic Ca2+ binds to calmodulin (CaM) and activates the phosphatase calcineurin (Cn) and CaM kinase (CaMKII). Cn dephosphorylates cytoplasmic nuclear factor of activated T-cells (NFAT), inducing its translocation to the nucleus where it activates anti-apoptotic and hypertrophic target genes. Cytoplasmic CaMKII regulates Ca2+ handling proteins but whether or not it is directly involved in hypertrophic and survival signaling is not known.
This study explored the hypothesis that cytoplasmic CaMKII reduces NFAT nuclear translocation by inhibiting the phosphatase activity of Cn.
Methods and Results
GFP-tagged NFATc3 was used to determine the cellular location of NFAT in cultured neonatal rat ventricular myocytes (NRVM) and adult feline ventricular myocytes. Constitutively active (CaMKII-CA) or dominant negative (CaMKII-DN) mutants of cytoplasmic targeted CaMKIIδc were used to activate and inhibit cytoplasmic CaMKII activity. In NRVM CaMKII-DN (48.5±3%, P<0.01 vs control) increased while CaMKII-CA decreased (5.9±1%, P<0.01 vs control) NFAT nuclear translocation (Control: 12.3±1%). Cn inhibitors were used to show that these effects were caused by modulation of Cn activity. Increasing Ca2+ increased Cn-dependent NFAT translocation (to 71.7±7%, p<0.01) and CaMKII-CA reduced this effect (to 17.6±4%). CaMKII-CA increased TUNEL and caspase-3 activity (P<0.05). CaMKII directly phosphorylated Cn at Ser197 in CaMKII-CA infected NRVM and in hypertrophied feline hearts.
These data show that activation of cytoplasmic CaMKII inhibits NFAT nuclear translocation by phosphorylation and subsequent inhibition of Cn.
PMCID: PMC2765687  PMID: 19608982
CaMKII; Calcineurin; NFAT; Myocytes; Heart Disease
4.  CaMKII is involved in cadmium activation of MAPK and mTOR pathways leading to neuronal cell death 
Journal of neurochemistry  2011;119(5):1108-1118.
Cadmium (Cd), a toxic environmental contaminant, induces neurodegenerative diseases. Recently we have shown that Cd elevates intracellular free calcium ion ([Ca2+]i) level, leading to neuronal apoptosis partly by activating mitogen-activated protein kinases (MAPK) and mammalian target of rapamycin (mTOR) pathways. However, the underlying mechanism remains to be elucidated. Here we show that the effects of Cd elevated [Ca2+]i on MAPK and mTOR network as well as neuronal cell death are through stimulating phosphorylation of calcium/calmodulin-dependent protein kinase II (CaMKII). This is supported by the findings that chelating intracellular Ca2+ with BAPTA/AM or preventing Cd-induced [Ca2+]i elevation using 2-aminoethoxydiphenyl borate (2-APB) blocked Cd activation of CaMKII. Inhibiting CaMKII with KN93 or silencing CaMKII attenuated Cd activation of MAPK/mTOR pathways and cell death. Furthermore, inhibitors of mTOR (rapamycin), JNK (SP600125) and Erk1/2 (U0126), but not of p38 (PD169316), prevented Cd-induced neuronal cell death in part through inhibition of [Ca2+]i elevation and CaMKII phosphorylation. The results indicate that Cd activates MAPK/mTOR network triggering neuronal cell death, by stimulating CaMKII. Our findings underscore a central role of CaMKII in the neurotoxicology of Cd, and suggest that manipulation of intracellular Ca2+ level or CaMKII activity may be exploited for prevention of Cd-induced neurodegenerative disorders.
PMCID: PMC3217117  PMID: 21933187
cadmium; apoptosis; calcium ion; calcium/calmodulin-dependent protein kinase II; mitogen-activated protein kinase; mammalian target of rapamycin
5.  Neuroprotective activities of catalpol against CaMKII-dependent apoptosis induced by LPS in PC12 cells 
British Journal of Pharmacology  2013;169(5):1140-1152.
Background and Purpose
Neurodegenerative diseases present progressive neurological disorder induced by cell death or apoptosis. Catalpol, an iridoid glucoside isolated from the root of Rehmannia glutinosa Libosch, is present in a wide range of plant families. Although catalpol is an effective anti-apoptotic agent in LPS-induced neurodegeneration, the underlying mechanism has not been established. Here we have identified some of the mechanisms involved the prevention by catalpol of apoptosis induced by LPS in an experimental model of neurodegeneration in vitro.
Experimental Approach
Apoptosis was induced by adding LPS (80 ng·mL−1) to pheochromocytoma (PC12) cells, pretreated with catalpol for 12 h. We measured intracellular reactive oxygen species (ROS), apoptosis and intracellular calcium concentration ( [Ca2+]i) by flow cytometry or laser confocal scanning microscopy. We also analysed the protein expression of Bcl-2, Bax and Ca2+-calmodulin-dependent protein kinase II (CaMKII)-dependent apoptosis signal-regulating kinase-1 (ASK-1)/JNK/p38 signalling pathway in PC12 cells by Western blot.
Key Results
Catalpol stimulated expression of Bcl-2 and inhibited the expression of Bax. Catalpol also attenuated the increase in Ca2+ concentration induced by LPS in PC12 cells and down-regulated CaMK phosphorylation. The CaMKII-dependent ASK-1/JNK/p38 signalling cascade was blocked by catalpol. All these changes were accompanied by a decrease of apoptosis induced by LPS in PC12 cells.
Conclusions and Implications
The data presented here provide new mechanistic insights into the links between the CaMKII-dependent ASK-1/JNK/p38 signalling pathway and the protective effect of catalpol on apoptosis induced by LPS in PC12 cells.
PMCID: PMC3696335  PMID: 23550774
Catalpol; neurodegenerative diseases; LPS; apoptosis; CaMKII; ASK-1/JNK/p38
6.  Cardioprotection by CaMKII-δB Is Mediated by Phosphorylation of HSF1 and Subsequent Expression of Inducible HSP70 
Circulation research  2009;106(1):102.
Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a multifunctional kinase involved in vital cellular processes such as Ca2+ handling and cell fate regulation. In mammalian heart, two primary CaMKII isoforms, δB and δC, localize in nuclear and cytosolic compartments, respectively. Although previous studies have established an essential role of CaMKII-δC in cardiomyocyte apoptosis, the functional role of the more abundant isoform, CaMKII-δB, remains elusive.
Here we determined the potential role of CaMKII-δB in regulating cardiomyocyte viability and explored the underlying mechanism.
Methods and Results
In cultured neonatal rat cardiomyocytes, the expression of CaMKII-δB and CaMKII-δC was inversely regulated in response to H2O2-induced oxidative stress with a profound reduction of the former and an increase of the later. Similarly, in vivo ischemia/repefusion (IR) led to an opposite regulation of these CaMKII isoforms in a rat myocardial IR model. Notably, overexpression of CaMKII-δB protected cardiomyocytes against oxidative stress-, hypoxia- and angiotensin II-induced apoptosis, whereas overexpression of its cytosolic counterpart promoted apoptosis. Using cDNA microarray, real time-PCR and Western blotting, we demonstrated that overexpression of CaMKII-δB but not CaMKII-δC elevated expression of heat shock protein 70 (HSP70) family members, including inducible HSP70 (iHSP70) and its homologous (Hst70). Moreover, overexpression of CaMKII-δB led to phosphorylation and activation of heat shock factor 1 (HSF1), the primary transcription factor responsible for HSP70 gene regulation. Importantly, gene silencing of iHSP70, but not Hst70, abolished CaMKII-δB-mediated protective effect, indicating that only iHSP70 was required for CaMKII-δB elicited anti-apoptotic signaling.
We conclude that cardiac CaMKII-δB and CaMKII-δC were inversely regulated in response to oxidative stress and IR injury, and that in contrast to CaMKII-δC, CaMKII-δB serves as a potent suppressor of cardiomyocyte apoptosis triggered by multiple death-inducing stimuli via phosphorylation of HSF1 and subsequent induction of iHSP70, marking both CaMKII-δ isoforms as promising therapeutic targets for the treatment of ischemic heart disease.
PMCID: PMC2815328  PMID: 19910575
CaMKII isoforms; CaMKII-δB; oxidative stress; hypoxia; cardiomyocyte apoptosis; iHSP70; HSF1
7.  CaMKII Is Essential for the Function of the Enteric Nervous System 
PLoS ONE  2012;7(8):e44426.
Ca2+/calmodulin-dependent protein kinases (CaMKs) are major downstream mediators of neuronal calcium signaling that regulate multiple neuronal functions. CaMKII, one of the key CaMKs, plays a significant role in mediating cellular responses to external signaling molecules. Although calcium signaling plays an essential role in the enteric nervous system (ENS), the role of CaMKII in neurogenic intestinal function has not been determined. In this study, we investigated the function and expression pattern of CaMKII in the ENS across several mammalian species.
Methodology/Principal Findings
CaMKII expression was characterized by immunofluorescence analyses and Western Blot. CaMKII function was examined by intracellular recordings and by assays of colonic contractile activity. Immunoreactivity for CaMKII was detected in the ENS of guinea pig, mouse, rat and human preparations. In guinea pig ENS, CaMKII immunoreactivity was enriched in both nitric oxide synthase (NOS)- and calretinin-containing myenteric plexus neurons and non-cholinergic secretomotor/vasodilator neurons in the submucosal plexus. CaMKII immunoreactivity was also expressed in both cholinergic and non-cholinergic neurons in the ENS of mouse, rat and human. The selective CaMKII inhibitor, KN-62, suppressed stimulus-evoked purinergic slow EPSPs and ATP-induced slow EPSP-like response in guinea pig submucosal plexus, suggesting that CaMKII activity is required for some metabotropic synaptic transmissions in the ENS. More importantly, KN-62 significantly suppressed tetrodotoxin-induced contractile response in mouse colon, which suggests that CaMKII activity is a major determinant of the tonic neurogenic inhibition of this tissue.
ENS neurons across multiple mammalian species express CaMKII. CaMKII signaling constitutes an important molecular mechanism for controlling intestinal motility and secretion by regulating the excitability of musculomotor and secretomotor neurons. These findings revealed a fundamental role of CaMKII in the ENS and provide clues for the treatment of intestinal dysfunctions.
PMCID: PMC3432132  PMID: 22952977
8.  Structure of the CaMKIIδ/Calmodulin Complex Reveals the Molecular Mechanism of CaMKII Kinase Activation 
PLoS Biology  2010;8(7):e1000426.
Structural and biophysical studies reveal how CaMKII kinases, which are important for cellular learning and memory, are switched on by binding of Ca2+/calmodulin.
Long-term potentiation (LTP), a long-lasting enhancement in communication between neurons, is considered to be the major cellular mechanism underlying learning and memory. LTP triggers high-frequency calcium pulses that result in the activation of Calcium/Calmodulin (CaM)-dependent kinase II (CaMKII). CaMKII acts as a molecular switch because it remains active for a long time after the return to basal calcium levels, which is a unique property required for CaMKII function. Here we describe the crystal structure of the human CaMKIIδ/Ca2+/CaM complex, structures of all four human CaMKII catalytic domains in their autoinhibited states, as well as structures of human CaMKII oligomerization domains in their tetradecameric and physiological dodecameric states. All four autoinhibited human CaMKIIs were monomeric in the determined crystal structures but associated weakly in solution. In the CaMKIIδ/Ca2+/CaM complex, the inhibitory region adopted an extended conformation and interacted with an adjacent catalytic domain positioning T287 into the active site of the interacting protomer. Comparisons with autoinhibited CaMKII structures showed that binding of calmodulin leads to the rearrangement of residues in the active site to a conformation suitable for ATP binding and to the closure of the binding groove for the autoinhibitory helix by helix αD. The structural data, together with biophysical interaction studies, reveals the mechanism of CaMKII activation by calmodulin and explains many of the unique regulatory properties of these two essential signaling molecules.
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Author Summary
CaMKII enzymes transmit calcium ion (Ca2+) signals released inside the cell by regulating signal transduction pathways through phosphorylation: Ca2+ first binds to the small regulatory protein CaM; this Ca2+/CaM complex then binds to and activates the kinase, which phosphorylates other proteins in the cell. Since CaMKs remain active long after rapid Ca2+ pulses have dropped they function as molecular switches that turn on or off crucial cell functions in response to Ca2+ levels. The multifunctional CaMKII forms of this enzyme – of which there are four in human – are important in many processes including signaling in neurons and controlling of the heart rate. They are particularly abundant in the brain where they probably play a role in memory. CaMKII forms an exceptionally large, dodecameric complex. Here, we describe the crystal structure of this complex for each of the four human CaMKII catalytic domains in their autoinhibited states, a complex of CaMKII with Ca2+/CaM, as well as the structure of the oligomerization domain (the part of the protein that mediates complex formation) in its physiological dodecameric state and in a tetradecameric state. Detailed comparison of this large body of structural data together with biophysical studies has allowed us to better understand the structural mechanisms of CaMKII activation by CaM and to explain many of the complex regulatory features of these essential enzymes.
PMCID: PMC2910593  PMID: 20668654
9.  The Role of CaMKII in Calcium-Activated Death Pathways in Bone Marrow B Cells 
Toxicological Sciences  2010;118(1):108-118.
Calcium is an essential signaling molecule in developing B cells, thus altering calcium dynamics represents a potential target for toxicant effects. GW7845, a tyrosine analog and potent peroxisome proliferator-activated receptor γ agonist, induces rapid mitogen-activated protein kinase (MAPK)–dependent apoptosis in bone marrow B cells. Changes in calcium dynamics are capable of mediating rapid initiation of cell death; therefore, we investigated the contribution of calcium to GW7845-induced apoptosis. Treatment of a nontransformed murine pro/pre-B cell line (BU-11) with GW7845 (40μM) resulted in intracellular calcium release. Multiple features of GW7845-induced cell death were suppressed by the calcium chelator BAPTA, including MAPK activation, loss of mitochondrial membrane potential, cytochrome c release, caspase-3 activation, and DNA fragmentation. A likely mechanism for the calcium-mediated effects is activation of CaMKII, a calcium-dependent MAP4K. We observed that three CaMKII isoforms (β, γ, and δ) are expressed in lymphoid tissues and bone marrow B cells. Treatment with GW7845 increased CaMKII activity. All features of GW7845-induced cell death, except loss of mitochondrial membrane potential, were suppressed by CaMKII inhibitors (KN93 and AIP-II), suggesting the activation of multiple calcium-driven pathways. To determine if CaMKII activation is a common feature of early B cell death following perturbation of Ca2+ flux, we dissected tributyltin (TBT)-induced death signaling. High-dose TBT (1μM) is known to activate calcium-dependent death. TBT induced rapid apoptosis that was associated with intracellular calcium release, CaMKII activation and MAPK activation, and was inhibited by AIP-II. Thus, we show that early B cells are susceptible to calcium-triggered cell death through a CaMKII/MAPK-dependent pathway.
PMCID: PMC2955217  PMID: 20810541
bone marrow; B cells; CaMKII; apoptosis; MAPK
10.  Calcium/calmodulin-dependent protein kinase II links ER stress with Fas and mitochondrial apoptosis pathways 
The Journal of Clinical Investigation  2009;119(10):2925-2941.
ER stress–induced apoptosis is implicated in various pathological conditions, but the mechanisms linking ER stress–mediated signaling to downstream apoptotic pathways remain unclear. Using human and mouse cell culture and in vivo mouse models of ER stress–induced apoptosis, we have shown that cytosolic calcium resulting from ER stress induces expression of the Fas death receptor through a pathway involving calcium/calmodulin-dependent protein kinase IIγ (CaMKIIγ) and JNK. Remarkably, CaMKIIγ was also responsible for processes involved in mitochondrial-dependent apoptosis, including release of mitochondrial cytochrome c and loss of mitochondrial membrane potential. CaMKII-dependent apoptosis was also observed in a number of cultured human and mouse cells relevant to ER stress–induced pathology, including cultured macrophages, endothelial cells, and neuronal cells subjected to proapoptotic ER stress. Moreover, WT mice subjected to systemic ER stress showed evidence of macrophage mitochondrial dysfunction and apoptosis, renal epithelial cell apoptosis, and renal dysfunction, and these effects were markedly reduced in CaMKIIγ-deficient mice. These data support an integrated model in which CaMKII serves as a unifying link between ER stress and the Fas and mitochondrial apoptotic pathways. Our study also revealed what we believe to be a novel proapoptotic function for CaMKII, namely, promotion of mitochondrial calcium uptake. These findings raise the possibility that CaMKII inhibitors could be useful in preventing apoptosis in pathological settings involving ER stress–induced apoptosis.
PMCID: PMC2752072  PMID: 19741297
11.  Protein kinase C-α attenuates cholinergically stimulated gastric acid secretion of rabbit parietal cells 
British Journal of Pharmacology  2003;139(3):545-554.
The phorbolester 12-O-tetradecanoyl phorbol-13-acetate (TPA), an activator of protein kinase C (PKC), inhibits cholinergic stimulation of gastric acid secretion. We observed that this effect strongly correlated with the inhibition of Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity in rabbit parietal cells.The aim of this study was to specify the function of PKC-α in cholinergically stimulated H+ secretion. PKC-α represents the only calcium-dependent PKC isoenzyme that has been detected in rabbit parietal cells.Gö 6976, an inhibitor of calcium-dependent PKC, concentration-dependently antagonized the inhibitory effect of TPA, and, therefore, revealed the action of PKC-α on carbachol-induced acid secretion in rabbit parietal cells.TPA exerted no additive inhibition of carbachol-stimulated acid secretion if acid secretion was partially inhibited by the potent CaMKII inhibitor 1-[N,O-bis(5-isoquinolinsulfonyl)-N-methyl-L-tyrosyl]-4-phenyl-piperazine (KN-62).Since both kinase modulators, TPA and KN-62, affected no divergent signal transduction pathways in the parietal cell, an in vitro model has been used to study if PKC directly targets CaMKII. CaMKII purified from parietal cell-containing gastric mucosa of pig, was transphosphorylated by purified cPKC containing PKC-α up to 1.8 mol Pi per mol CaMKII in vitro. The autonomy site of CaMKII was not transphosphorylated by PKC.The phosphotransferase activity of the purified CaMKII was in vitro inhibited after transphosphorylation by PKC if calmodulin was absent during transphosphorylation. Attenuation of CaMKII activity by PKC showed strong similarity to the downregulation of CaMKII by basal autophosphorylation.Our results suggest that PKC-α and CaMKII are closely functionally linked in a cholinergically induced signalling pathway in rabbit parietal cells. We assume that in cholinergically stimulated parietal cells PKC-α transinhibits CaMKII activity, resulting in an attenuation of acid secretion.
PMCID: PMC1573865  PMID: 12788814
Calcium; Ca2+/calmodulin-dependent protein kinase; carbachol; gastric acid secretion; indolocarbazole; parietal cell; phorbol ester; protein kinase C; protein kinase inhibition
12.  Role of activated CaMKII in abnormal calcium homeostasis and INa remodeling after myocardial infarction: Insights from mathematical modeling 
Ca2+/calmodulin-dependent protein kinase II is a multifunctional serine/threonine kinase with diverse cardiac roles including regulation of excitation contraction, transcription, and apoptosis. Dynamic regulation of CaMKII activity occurs in cardiac disease and is linked to specific disease phenotypes through its effects on ion channels, transporters, transcription and cell death pathways. Recent mathematical models of the cardiomyocyte have incorporated limited elements of CaMKII signaling to advance our understanding of how CaMKII regulates cardiac contractility and excitability. Given the importance of CaMKII in cardiac disease, it is imperative that computer models evolve to capture the dynamic range of CaMKII activity. In this study, using mathematical modeling combined with biochemical and imaging techniques, we test the hypothesis that CaMKII signaling in the canine infarct border zone (BZ) contributes to impaired calcium homeostasis and electrical remodeling. We report that the level of CaMKII autophosphorylation is significantly increased in the BZ region. Computer simulations using an updated mathematical model of CaMKII signaling reproduce abnormal Ca2+ transients and action potentials characteristic of the BZ. Our simulations show that CaMKII hyperactivity contributes to abnormal Ca2+ homeostasis and reduced action potential upstroke velocity due to effects on INa gating kinetics. In conclusion, we present a new mathematical tool for studying effects of CaMKII signaling on cardiac excitability and contractility over a dynamic range of kinase activities. Our experimental and theoretical findings establish abnormal CaMKII signaling as an important component of remodeling in the canine BZ.
PMCID: PMC2587155  PMID: 18639555
Calcium/calmodulin-dependent protein kinase II; myocardial infarction; calcium handling; mathematical modeling; arrhythmia
13.  Calcium/calmodulin‐dependent kinase II and nitric oxide synthase 1‐dependent modulation of ryanodine receptors during β‐adrenergic stimulation is restricted to the dyadic cleft 
The Journal of Physiology  2016;594(20):5923-5939.
Key points
The dyadic cleft, where coupled ryanodine receptors (RyRs) reside, is thought to serve as a microdomain for local signalling, as supported by distinct modulation of coupled RyRs dependent on Ca2+/calmodulin‐dependent kinase II (CaMKII) activation during high‐frequency stimulation.Sympathetic stimulation through β‐adrenergic receptors activates an integrated signalling cascade, enhancing Ca2+ cycling and is at least partially mediated through CaMKII.Here we report that CaMKII activation during β‐adrenergic signalling is restricted to the dyadic cleft, where it enhances activity of coupled RyRs thereby contributing to the increase in diastolic events. Nitric oxide synthase 1 equally participates in the local modulation of coupled RyRs.In contrast, the increase in the Ca2+ content of the sarcoplasmic reticulum and related increase in the amplitude of the Ca2+ transient are primarily protein kinase A‐dependent.The present data extend the concept of microdomain signalling in the dyadic cleft and give perspectives for selective modulation of RyR subpopulations and diastolic events.
In cardiac myocytes, β‐adrenergic stimulation enhances Ca2+ cycling through an integrated signalling cascade modulating L‐type Ca2+ channels (LTCCs), phospholamban and ryanodine receptors (RyRs). Ca2+/calmodulin‐dependent kinase II (CaMKII) and nitric oxide synthase 1 (NOS1) are proposed as prime mediators for increasing RyR open probability. We investigate whether this pathway is confined to the high Ca2+ microdomain of the dyadic cleft and thus to coupled RyRs. Pig ventricular myocytes are studied under whole‐cell voltage‐clamp and confocal line‐scan imaging with Fluo‐4 as a [Ca2+]i indicator. Following conditioning depolarizing pulses, spontaneous RyR activity is recorded as Ca2+ sparks, which are assigned to coupled and non‐coupled RyR clusters. Isoproterenol (ISO) (10 nm) increases Ca2+ spark frequency in both populations of RyRs. However, CaMKII inhibition reduces spark frequency in coupled RyRs only; NOS1 inhibition mimics the effect of CaMKII inhibition. Moreover, ISO induces the repetitive activation of coupled RyR clusters through CaMKII activation. Immunostaining shows high levels of CaMKII phosphorylation at the dyadic cleft. CaMKII inhibition reduces I CaL and local Ca2+ transients during depolarizing steps but has only modest effects on amplitude or relaxation of the global Ca2+ transient. In contrast, protein kinase A (PKA) inhibition reduces spark frequency in all RyRs concurrently with a reduction of sarcoplasmic reticulum Ca2+ content, Ca2+ transient amplitude and relaxation. In conclusion, CaMKII activation during β‐adrenergic stimulation is restricted to the dyadic cleft microdomain, enhancing LTCC‐triggered local Ca2+ release as well as spontaneous diastolic Ca2+ release whilst PKA is the major pathway increasing global Ca2+ cycling. Selective CaMKII inhibition may reduce potentially arrhythmogenic release without negative inotropy.
Key points
The dyadic cleft, where coupled ryanodine receptors (RyRs) reside, is thought to serve as a microdomain for local signalling, as supported by distinct modulation of coupled RyRs dependent on Ca2+/calmodulin‐dependent kinase II (CaMKII) activation during high‐frequency stimulation.Sympathetic stimulation through β‐adrenergic receptors activates an integrated signalling cascade, enhancing Ca2+ cycling and is at least partially mediated through CaMKII.Here we report that CaMKII activation during β‐adrenergic signalling is restricted to the dyadic cleft, where it enhances activity of coupled RyRs thereby contributing to the increase in diastolic events. Nitric oxide synthase 1 equally participates in the local modulation of coupled RyRs.In contrast, the increase in the Ca2+ content of the sarcoplasmic reticulum and related increase in the amplitude of the Ca2+ transient are primarily protein kinase A‐dependent.The present data extend the concept of microdomain signalling in the dyadic cleft and give perspectives for selective modulation of RyR subpopulations and diastolic events.
PMCID: PMC5063942  PMID: 27121757
14.  Ethanol Inhibition of Recombinant NMDA Receptors Is Not Altered by Co-Expression of CaMKII-α or CaMKII-β 
Alcohol (Fayetteville, N.Y.)  2008;42(5):425-432.
Previous studies have shown that the N-methyl-D-aspartate (NMDA) receptor is an important target for the actions of ethanol in the brain. NMDA receptors are glutamate-activated ion channels that are highly expressed in neurons. They are activated during periods of significant glutamatergic synaptic activity and are an important source of the signaling molecule calcium in the post-synaptic spine. Alterations in the function of NMDA receptors by drugs or disease are associated with deficits in motor, sensory and cognitive processes of the brain. Acutely, ethanol inhibits ion flow through NMDA receptors while sustained exposure to ethanol can induce compensatory changes in the density and localization of the receptor. Defining factors that govern the acute ethanol sensitivity of NMDA receptors is an important step in how an individual responds to ethanol. In the present study, we investigated the effect of calcium-calmodulin dependent protein kinase II (CaMKII) on the ethanol sensitivity of recombinant NMDA receptors. CaMKII is a major constituent of the post-synaptic density and is critically involved in various forms of learning and memory. NMDA receptor subunits were transiently expressed in human embryonic kidney 293 cells (HEK 293) along with CaMKII-α or CaMKII-β tagged with the green fluorescent protein (GFP). Whole cell currents were elicited by brief exposures to glutamate and were measured using patchclamp electrophysiology. Neither CaMKII-α or CaMKII-β had any significant effect on the ethanol inhibition of NR1/2A or NR1/2B receptors. Ethanol inhibition was also unaltered by deletion of CaMKII binding domains in NR1 or NR2 subunits or by phospho-site mutants that mimic or occlude CaMKII phosphorylation. Chronic treatment of cortical neurons with ethanol had no significant effect on the expression of CaMKII-α or CaMKII-β. The results of this study suggest that CaMKII is not involved in regulating the acute ethanol sensitivity of NMDA receptors.
PMCID: PMC2629600  PMID: 18562151
electrophysiology; alcohol; ion channel; kinase; phosphorylation
15.  Targeting the CaMKII/ERK Interaction in the Heart Prevents Cardiac Hypertrophy 
PLoS ONE  2015;10(6):e0130477.
Activation of Ca2+/Calmodulin protein kinase II (CaMKII) is an important step in signaling of cardiac hypertrophy. The molecular mechanisms by which CaMKII integrates with other pathways in the heart are incompletely understood. We hypothesize that CaMKII association with extracellular regulated kinase (ERK), promotes cardiac hypertrophy through ERK nuclear localization.
Methods and Results
In H9C2 cardiomyoblasts, the selective CaMKII peptide inhibitor AntCaNtide, its penetratin conjugated minimal inhibitory sequence analog tat-CN17β, and the MEK/ERK inhibitor UO126 all reduce phenylephrine (PE)-mediated ERK and CaMKII activation and their interaction. Moreover, AntCaNtide or tat-CN17β pretreatment prevented PE induced CaMKII and ERK nuclear accumulation in H9C2s and reduced the hypertrophy responses. To determine the role of CaMKII in cardiac hypertrophy in vivo, spontaneously hypertensive rats were subjected to intramyocardial injections of AntCaNtide or tat-CN17β. Left ventricular hypertrophy was evaluated weekly for 3 weeks by cardiac ultrasounds. We observed that the treatment with CaMKII inhibitors induced similar but significant reduction of cardiac size, left ventricular mass, and thickness of cardiac wall. The treatment with CaMKII inhibitors caused a significant reduction of CaMKII and ERK phosphorylation levels and their nuclear localization in the heart.
These results indicate that CaMKII and ERK interact to promote activation in hypertrophy; the inhibition of CaMKII-ERK interaction offers a novel therapeutic approach to limit cardiac hypertrophy.
PMCID: PMC4481531  PMID: 26110816
16.  Linkage of β1-adrenergic stimulation to apoptotic heart cell death through protein kinase A–independent activation of Ca2+/calmodulin kinase II 
Journal of Clinical Investigation  2003;111(5):617-625.
β1-adrenergic receptor (β1AR) stimulation activates the classic cAMP/protein kinase A (PKA) pathway to regulate vital cellular processes from the change of gene expression to the control of metabolism, muscle contraction, and cell apoptosis. Here we show that sustained β1AR stimulation promotes cardiac myocyte apoptosis by activation of Ca2+/calmodulin kinase II (CaMKII), independently of PKA signaling. β1AR-induced apoptosis is resistant to inhibition of PKA by a specific peptide inhibitor, PKI14-22, or an inactive cAMP analogue, Rp-8-CPT-cAMPS. In contrast, the β1AR proapoptotic effect is associated with non–PKA-dependent increases in intracellular Ca2+ and CaMKII activity. Blocking the L-type Ca2+ channel, buffering intracellular Ca2+, or inhibiting CaMKII activity fully protects cardiac myocytes against β1AR-induced apoptosis, and overexpressing a cardiac CaMKII isoform, CaMKII-δC, markedly exaggerates the β1AR apoptotic effect. These findings indicate that CaMKII constitutes a novel PKA-independent linkage of β1AR stimulation to cardiomyocyte apoptosis that has been implicated in the overall process of chronic heart failure.
PMCID: PMC151893  PMID: 12618516
17.  Dynamic Kv4.3–CaMKII unit in heart: an intrinsic negative regulator for CaMKII activation 
European Heart Journal  2010;32(3):305-315.
Reduction of transient outward current (Ito) and excessive activation of Ca2+/Calmodulin-dependent kinase II (CaMKII) are general features of ventricular myocytes in heart failure. We hypothesize that alterations of Ito directly regulate CaMKII activation in cardiomyocytes.
Methods and results
A dynamic coupling of Ito channel subunit Kv4.3 and inactive CaMKII was discovered in cardiomyocytes with the membrane predominant distribution by co-immunoprecipitation and fluorescence resonance energy transfer techniques. CaMKII dissociation from Kv4.3–CaMKII units caused a significant increase in CaMKII autophosphorylation and L-type calcium current (ICa) facilitation. ICa facilitation was blunted by the compartmental Ca2+ chelator BAPTA but unaffected by bulk Ca2+ chelator EGTA, implicating membrane-localized CaMKII. Kv4.3 overexpression reduced basal CaMKII autophosphorylation in myocytes and eliminated Ca2+-induced CaMKII activation. Kv4.3 blocks CaMKII activation by binding to the calmodulin binding sites, whereas Kv4.3 uncoupling releases these sites and leads to a substantial CaMKII activation.
Our results uncovered an important mechanism that regulates CaMKII activation in the heart and implicate Ito channel alteration in pathological CaMKII activation.
PMCID: PMC3031792  PMID: 21148163
Heart failure; CaMKII; Ito channel; Kv4.3; Myocytes
18.  Molecular mechanism of activation-triggered subunit exchange in Ca2+/calmodulin-dependent protein kinase II 
eLife  null;5:e13405.
Activation triggers the exchange of subunits in Ca2+/calmodulin-dependent protein kinase II (CaMKII), an oligomeric enzyme that is critical for learning, memory, and cardiac function. The mechanism by which subunit exchange occurs remains elusive. We show that the human CaMKII holoenzyme exists in dodecameric and tetradecameric forms, and that the calmodulin (CaM)-binding element of CaMKII can bind to the hub of the holoenzyme and destabilize it to release dimers. The structures of CaMKII from two distantly diverged organisms suggest that the CaM-binding element of activated CaMKII acts as a wedge by docking at intersubunit interfaces in the hub. This converts the hub into a spiral form that can release or gain CaMKII dimers. Our data reveal a three-way competition for the CaM-binding element, whereby phosphorylation biases it towards the hub interface, away from the kinase domain and calmodulin, thus unlocking the ability of activated CaMKII holoenzymes to exchange dimers with unactivated ones.
eLife digest
How does memory outlast the lifetime of the molecules that encode it? One enzyme that is found in neurons and has been suggested to help long-term memories to form is called CaMKII. Each CaMKII assembly is typically composed of 12 to 14 protein subunits associated in a ring and can exist in either an “unactivated” or “activated” state. In 2014, researchers showed that CaMKII assemblies can exchange subunits with each other. Importantly, an active CaMKII can mix with an unactivated CaMKII and share its activation state. CaMKII may use this mechanism to spread information to the next generation of proteins – thereby allowing activation to outlast the lifespan of the initially activated proteins. However the molecular mechanism that underlies this process was not clear.
Now, Bhattacharyya et al. – including some of the researchers involved in the 2014 work – address two questions about this mechanism. How do subunits exchange between CaMKII assemblies? And how does the activation of CaMKII initiate subunit exchange?
A closed-ring hub ties the subunits of CaMKII together, similar to the organization of the segments in an orange. To undergo subunit exchange, the hub must open up to release and accept subunits. Bhattacharyya et al. have now uncovered an intrinsic flexibility in the hub that is triggered by a short peptide segment in CaMKII. This segment, which is exposed in activated CaMKII but not in the unactivated form, can crack open the hub ring by binding between the hub subunits, like a finger separating the segments of an orange. This allows the hub to flex and expand, and once open, the hub’s flexibility allows room for subunits to be released or accepted.
Although this subunit exchange mechanism could be a powerful means for spreading the activated state throughout signaling pathways, the biological relevance of this phenomenon has not been clarified. However, the mechanistic framework provided by Bhattacharyya et al. may allow new experiments to be performed that test the consequences of subunit exchange in live cells and organisms. It could also enable investigations into the importance of subunit exchange in long-term memory.
PMCID: PMC4859805  PMID: 26949248
subunit exchange; structural transition; kinase activation; Ca2+/CaM stimulus; E. coli; S. rosetta; N. vectensis
19.  MyD88 mediated inflammatory signaling leads to CaMKII oxidation, cardiac hypertrophy and death after myocardial infarction. 
The toll-like receptors (TLR) and myocardial infarction (MI) promote NF-κB-dependent inflammatory transcription and oxidative injury in myocardium. The multifunctional Ca2+/calmodulin-dependent protein kinase II (CaMKII) is activated by oxidation and contributes to NF-κB-dependent transcription, myocardial hypertrophy and post-MI death. The myeloid differentiation protein 88 (MyD88) is an adapter protein critical for many TLR functions, but downstream targets for TLR/MyD88 signaling in MI are not well understood. We asked if CaMKII and TLR/MyD88 pathways are interconnected and if TLR/MyD88 contributes to adverse outcomes after MI. Here we show that TLR-4 activation by lipopolysaccharide (LPS) induces CaMKII oxidation (ox-CaMKII) in cardiomyocytes. MI enhances ox-CaMKII in wild type (WT) hearts but not in MyD88−/− hearts that are defective in MyD88-dependent TLR signaling. In post-MI WT hearts expression of pro-inflammatory genes TNF-α (Tnfa), complement factor B (Cfb), myocyte death and fibrosis were significatly increased, but increases were significantly less in MyD88−/− hearts after MI. MyD88−/− cardiomyocytes were defective in NF-κB activation by LPS but not by the MyD88-independent TLR agonist poly(I:C). In contrast, TNF-α induced Cfb gene expression was not deficient in MyD88−/− cardiomyocytes. Several hypertrophy marker genes were upregulated in both WT and MyD88−/− hearts after MI, but Acta1 was significantly attenuated in MyD88−/− hearts, suggesting that MyD88 selectively affects expression of hypertrophic genes. Post-MI cardiac hypertrophy, inflammation, apoptosis, ox-CaMKII expression and mortality were significantly reduced in MyD88−/− compared to WT littermates. These data suggest that MyD88 contributes to CaMKII oxidation and is important for adverse hypertrophic and inflammatory responses to LPS and MI.
PMCID: PMC3327770  PMID: 22326848
Myocardial infarction; Hypertrophy; Inflammation; Oxidant stress; CaMKII; Innate Immunity
20.  On the possible role of ERK, p38 and CaMKII in the regulation of CGRP expression in morphine-tolerant rats 
Molecular Pain  2011;7:68.
The neuropeptide, calcitonin gene-related peptide (CGRP) has been proposed to be a regulator of the development of morphine analgesic tolerance and thereby could be a target to reduce the induction of this phenomenon under clinical conditions. However, the mechanisms of CGRP regulation are unclear. We investigated here the possible role of the extracellular signal-regulated protein kinase (ERK), p38 and calcium/calmodulin-dependent protein kinase II (CaMKII) in CGRP regulation following chronic morphine treatment.
A 7-day treatment with morphine (15 μg/day) led to an increase in CGRP contents in the spinal cord dorsal horn (SCDH) and dorsal root ganglion (DRG) and this effect was prevented by the inhibition of the ERK, p38 or CaMKII pathway. The phosphorylation/activation of ERK, p38 and CaMKII was enhanced in the SCDH following chronic morphine while in DRG only the phosphorylation of CaMKII was increased. Moreover, our chronic morphine treatment up-regulated neuronal nitric oxide synthase (nNOS) levels in the SCDH, an effect blocked by the inhibition of the ERK, p38 or CaMKII pathway. The blockade of nNOS activity also suppressed chronic morphine-induced CGRP increases in the DRG and SCDH. Double immunofluorescence studies revealed that nNOS and CaMKII are co-localized in the SCDH and that CaMKII is activated in CGRP-expressing DRG neurons.
The activation of spinal ERK, p38 and CaMKII, alongside nNOS, is involved in chronic morphine-induced CGRP up-regulation in both the DRG and SCDH. Moreover, the stimulation of CaMKII in the DRG likely directly regulates the expression of CGRP associated with morphine analgesic tolerance.
PMCID: PMC3190348  PMID: 21933441
CGRP; ERK; p38; CaMKII; morphine
21.  Activation-triggered subunit exchange between CaMKII holoenzymes facilitates the spread of kinase activity 
eLife  2014;3:e01610.
The activation of the dodecameric Ca2+/calmodulin dependent kinase II (CaMKII) holoenzyme is critical for memory formation. We now report that CaMKII has a remarkable property, which is that activation of the holoenzyme triggers the exchange of subunits between holoenzymes, including unactivated ones, enabling the calcium-independent phosphorylation of new subunits. We show, using a single-molecule TIRF microscopy technique, that the exchange process is triggered by the activation of CaMKII, and that exchange is modulated by phosphorylation of two residues in the calmodulin-binding segment, Thr 305 and Thr 306. Based on these results, and on the analysis of molecular dynamics simulations, we suggest that the phosphorylated regulatory segment of CaMKII interacts with the central hub of the holoenzyme and weakens its integrity, thereby promoting exchange. Our results have implications for an earlier idea that subunit exchange in CaMKII may have relevance for information storage resulting from brief coincident stimuli during neuronal signaling.
eLife digest
How do fleeting signals passing through the neurons of our brains become memories that can last for years or even decades? An enzyme called CaMKII is known to have an important role in the formation of memories. CaMKII adds phosphate groups to proteins—a process that is called phosphorylation—and is itself activated when calcium levels increase inside the neurons where the enzyme is found.
Individual CaMKII proteins bind together in groups of 12 to form a ‘holoenzyme’. When one of the 12 subunits is activated by calcium, it can phosphorylate the other subunits in the same holoenzyme. Once this happens, the activation of CaMKII can continue after the initial rise in calcium has ceased, and this effect is thought to be involved in the formation of long-term memories.
30 years ago, Francis Crick—famous for his role in the discovery of the double helix—proposed that memory formation might involve ‘memory-storage molecules’ passing an activated state to unactivated molecules, and John Lisman later suggested that CaMKII could fulfil this role by swapping subunits of holoenzymes between activated and unactivated ones. Now, Stratton, Lee et al. have tested whether CaMKII can exchange subunits by using advanced microscopy to track single molecules of CaMKII labelled with fluorescent markers. This revealed that activation can cause CaMKII subunits repeatedly to mix between holoenzymes—and this only happens once a first holoenzyme has been activated.
Subunits of CaMKII join together via a central ‘hub’ region, but when a subunit is activated, the phosphorylated segment may interact with the hub. This weakens the connections between the subunits, thereby making it easier for subunits to exchange between holoenzymes. This process provides a mechanism by which a level of activated CaMKII can be maintained, even if some subunits become degraded and long after the disappearance of the initial activation signal.
PMCID: PMC3901001  PMID: 24473075
CaMKII; subunit exchange; spread of activation state; single-molecule; E. coli
22.  Signaling Components of the 1α,25(OH)2D3-Dependent Pdia3 Receptor Complex Are Required for Wnt5a Calcium-Dependent Signaling 
Biochimica et biophysica acta  2014;1843(11):2365-2375.
Wnt5a and 1α,25(OH)2D3 are important regulators of endochondral ossification. In osteoblasts and growth plate chondrocytes, 1α,25(OH)2D3 initiates rapid effects via its membrane-associated receptor protein disulfide isomerase A3 (Pdia3) in caveolae, activating phospholipase A2 (PLA2)-activating protein (PLAA), calcium/calmodulin-dependent protein kinase II (CaMKII), and PLA2, resulting in protein kinase C (PKC) activation. Wnt5a initiates its calcium-dependent effects via intracellular calcium release, activating PKC and CaMKII. We investigated the requirement for components of the Pdia3 receptor complex in Wnt5a calcium-dependent signaling. We determined that Wnt5a signals through a CaMKII/PLA2/PGE2/PKC cascade. Silencing or blocking Pdia3, PLAA, or vitamin D receptor (VDR), and inhibition of calmodulin (CaM), CaMKII, or PLA2 inhibited Wnt5a-induced PKC activity. Wnt5a activated PKC in Caveolin-1-silenced cells, but methyl-beta-cyclodextrin reduced its stimulatory effect. 1α,25(OH)2D3 reduced stimulatory effects of Wnt5a on PKC in a dose-dependent manner. In contrast, Wnt5a had a biphasic effect on 1α,25(OH)2D3-stimulated PKC activation; 50ng/ml Wnt5a caused a 2-fold increase in 1α,25(OH)2D3-stimulated PKC but higher Wnt5a concentrations reduced 1α,25(OH)2D3-stimulated PKC activation. Western blots showed that Wnt receptors Frizzled2 (FZD2) and Frizzled5 (FZD5), and receptor tyrosine kinase-like orphan receptor 2 (ROR2) were localized to caveolae. Blocking ROR2, but not FZD2 or FZD5, abolished the stimulatory effects of 1α,25(OH)2D3 on PKC and CaMKII. 1α,25(OH)2D3 membrane receptor complex components (Pdia3, PLAA, Caveolin-1, CaM) interacted with Wnt5a receptors/co-receptors (ROR2, FZD2, FZD5) in immunoprecipitation studies, interactions that changed with either 1α,25(OH)2D3 or Wnt5a treatment. This study demonstrates that 1α,25(OH)2D3 and Wnt5a mediate their effects via similar receptor components and suggests that these pathways may interact.
PMCID: PMC4287416  PMID: 24946135
1,25-Dihydroxy vitamin D3; 1α,25(OH)2D3; Wnt5a; Pdia3; PLAA; PKC; MC3T3-E1 osteoblast-like cells; Costochondral cartilage growth zone chondrocytes
23.  Estrogen-induced Signaling Attenuates Soluble Aβ Peptide-Mediated Dysfunction of Pathways in Synaptic Plasticity 
Brain research  2011;1383:1-12.
Neuromodulation of synaptic plasticity by 17β-estradiol (E2) is thought to influence information processing and storage in the cortex and hippocampus. Because E2 rapidly affects cortical memory and synaptic plasticity, we examined its effects on phosphorylation of calcium/calmodulin-dependent protein kinase II (CaMKII), extracellular signal-regulated kinase (ERK), and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) [AMPA-type glutamate receptor subunit 1 (GluR1 subunit)], all of which are important for the induction and maintenance of synaptic plasticity and memory. Acute E2 treatment resulted in an increased temporal and spatial phosphorylation pattern of CaMKII, ERK, and AMPAR (GluR1 subunit). By using inhibitors, we were able to attribute GluR1 phosphorylation to CaMKII at serine 831, and we also found that E2 treatment increased GluR1 insertion into the surface membrane. Because soluble amyloid-beta (Aβ) oligomers inhibit CaMKII and ERK activation, which is necessary for synaptic plasticity, we also tested E2’s ability to ameliorate Aβ-induced dysfunction of synaptic plasticity. We found that estrogen treatment in neuronal culture, slice culture, and in vivo, ameliorated Aβ oligomer-induced inhibition of CaMKII, ERK, and AMPAR phosphorylation, and also ameliorated the Aβ oligomer-induced reduction of dendritic spine density in a CaMKII-dependent manner. These phosphorylation events are correlated with the early stage of inhibitory avoidance learning, and our data show that E2 improved inhibitory avoidance memory deficits in animals treated with soluble Aβ oligomers. This study identifies E2-induced signaling that attenuates soluble Aβ peptide-mediated dysfunction of pathways in synaptic plasticity.
PMCID: PMC3065978  PMID: 21262203
17β-estradiol; CaMKII; ERK; GluR1; synaptic plasticity
24.  Different actions of protein kinase C isoforms α and ε on gastric acid secretion 
British Journal of Pharmacology  2002;136(6):938-946.
The phorbol ester TPA, an activator of protein kinase C (PKC), inhibits cholinergic stimulation of gastric acid secretion but increases basal H+ secretion.Since these contradictory findings suggest the action of different PKC isozymes we analysed the role of calcium-dependent PKC-α, and calcium-independent PKC-ε in gastric acid secretion.Inhibition of PKC-α by the indolocarbazole Gö 6976 revealed that about 28% of carbachol-induced acid secretion was inhibited by PKC-α. In the presence of Gö 6976 approximately 64% of the carbachol-induced signal transduction is mediated by Ca2+/calmodulin-dependent protein kinase II (CaMKII), and 14% is conveyed by PKC-ε as deduced from the inhibition with the bisindolylmaleimide Ro 31-8220.Inhibition of carbachol-induced acid secretion by TPA was accompanied by a decrease in CaMKII activity.The stimulation of basal acid secretion by TPA was biphasic with a peak at a very low concentration (10 pM), resulting in an activation of the calcium-sensor CaMKII. The activation was determined with a phosphospecific polyclonal antibody against active CaMKII. The TPA-induced increase of H+ secretion was sensitive to the cell-permeable Ca2+-chelator BAPTA/AM, Ro 31-8220, and the CaMKII-inhibitor KN-62, but not to Gö 6976.Since TPA induced the translocation of PKC-ε but not of PKC-α in resting parietal cells, PKC-ε seems to be at least responsible for an initial elevation of free intracellular calcium to initiate TPA-induced acid secretion.Our data indicate the different roles of two PKC isoforms: PKC-ε activation appears to facilitate cholinergic stimulation of H+-secretion likely by increasing intracellular calcium. In contrast, PKC-α activation attenuates acid secretion accompanied by a down-regulation of CaMKII activity.
PMCID: PMC1573419  PMID: 12110618
Bisindolylmaleimide; Ca2+/calmodulin-dependent protein kinase; calcium; carbachol; gastric acid secretion; muscarinic acetylcholine receptor; phorbol ester; protein kinase C; protein kinase inhibition; signal transduction
25.  A dynamic pathway for calcium-independent activation of CaMKII by methionine oxidation 
Cell  2008;133(3):462-474.
Calcium/calmodulin (Ca2+/CaM)-dependent protein kinase II (CaMKII) couples increases in cellular Ca2+ to fundamental responses in excitable cells. CaMKII was identified over twenty years ago by activation dependence on Ca2+/CaM, but recent evidence shows CaMKII activity is also enhanced by pro-oxidant conditions. Here we show that oxidation of paired regulatory domain methionine residues sustains CaMKII activity in the absence of Ca2+/CaM. CaMKII is activated by angiotensin II (AngII) induced oxidation, leading to apoptosis in cardiomyocytes, both in vitro and in vivo. CaMKII oxidation is reversed by methionine sulfoxide reductase A (MsrA), and MsrA−/− mice show exaggerated CaMKII oxidation and myocardial apoptosis, impaired cardiac function, and increased mortality after myocardial infarction. Our data demonstrate a novel, dynamic mechanism for CaMKII activation by oxidation and highlight the critical importance of oxidation-dependent CaMKII activation to AngII and ischemic myocardial apoptosis.
PMCID: PMC2435269  PMID: 18455987

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