The cognitive deficits seen in schizophrenia patients are likely related to abnormal glutamatergic and cholinergic neurotransmission in the prefrontal cortex. We hypothesized that these impairments may be secondary to increased levels of the astrocyte-derived metabolite kynurenic acid (KYNA), which inhibits α7 nicotinic acetylcholine receptors (α7AChR) and may thereby reduce glutamate release. Using in vivo microdialysis in unanesthetized rats, we show here that nanomolar concentrations of KYNA, infused directly or produced in situ from its bioprecursor kynurenine, significantly decrease extracellular glutamate levels in the prefrontal cortex. This effect was prevented by the systemic administration of galantamine (3 mg/kg) but not by donepezil (2 mg/kg), indicating that KYNA blocks the allosteric potentiating site of the α7AChR, which recognizes galantamine but not donepezil as an agonist. In separate rats, reduction of prefrontal KYNA formation by (S)-4-ethylsulfonyl benzoylalanine, a specific inhibitor of KYNA synthesis, caused a significant elevation in extracellular glutamate levels. Jointly, our results demonstrate that fluctuations in endogenous KYNA formation bidirectionally influence cortical glutamate concentrations. These findings suggest that selective attenuation of cerebral KYNA production, by increasing glutamatergic tone, might improve cognitive function in individuals with schizophrenia.
Cognition; Donepezil; Galantamine; Kynurenine; Microdialysis; Prefrontal cortex
Spinal muscular atrophy, the most prevalent hereditary motor neuron disease, is caused by mutations in the survival motor neuron (SMN) 1 gene. A significant reduction in the encoded SMN protein leads to the degeneration of motor neurons. However, the molecular events leading to this process are not well understood. The present study uses a previously developed neuronal cell culture model of spinal muscular atrophy for a multiplex transcriptome analysis. Furthermore, gene expression analysis was performed on in vitro cell cultures, as well as tissue samples of spinal muscular atrophy patients and transgenic mice. RNA and subsequent Western blot protein analyses suggest that low SMN levels are associated with significantly lower alpha-synuclein expression. Examination of two genes related to vesicular transport showed a similar though less dramatic decrease in expression. The 140-amino acid protein alpha-synuclein, dominant mutations of which have previously been associated with an autosomal dominant form of Parkinson's disease, is strongly expressed in select neurons of the brain. Although not well understood, the physiologic functions of alpha-synuclein have been linked to synaptic vesicular neurotransmitter release and neuroprotection, suggesting a possible contribution to Smn-deficient motor neuron pathology. Furthermore, alpha-synuclein may be a genetic modifier or biomarker of spinal muscular atrophy.
Spinal muscular atrophy; Alpha-synuclein; Motor neuron disease; Survival motor neuron
Frontotemporal dementia is the second most common dementia among people under the age of 65. Fifty percent of affected patients have an associated family history. Several pathogenic genes have been identified for frontotemporal dementia associated with parkinsonism, including microtubule-associated protein tau, progranulin, and chromatin modifying protein 2B, and fused in sarcoma. It has also been reported that frontotemporal dementia associated with parkinsonism can be linked to chromosome 9p. In addition, there are families with frontotemporal dementia associated with a parkinsonian phenotype but unknown genetic status. Some of these kindreds have been diagnosed clinically as familial progressive supranuclear palsy, hereditary diffuse leukoencephalopathy with axonal spheroids, “overlap” syndrome, and others. Clinical presentation of frontotemporal dementia associated with parkinsonism is variable at age of symptomatic disease onset, disease duration, symptoms, and their occurrence during the disease course. Clinically, it is often difficult to sort out the different genetic forms of frontotemporal dementia associated with parkinsonism. However, with available clinical genetic testing for known genes, the precise diagnosis can be accomplished in some cases.
Familial; Frontotemporal dementia; Parkinsonism; MAPT; PGRN; 9p-linked
Some receptors that block axonal regeneration or promote cell death after spinal cord injury (SCI) are localized in membrane rafts. Flotillin-2 (Flot-2) is an essential protein associated with the formation of these domains and the clustering of membranal proteins, which may have signaling activities. Our hypothesis is that trauma will change Flot-2 expression and interference of this lipid raft marker will promote functional locomotor recovery after SCI. Analyses were conducted to determine the spatio-temporal profile of Flot-2 expression in adult rats after SCI, using the MASCIS impactor device. Immunoblots showed that SCI produced a significant decrease in the level of Flot-2 at 2 days post-injury (DPI) that increased until 28 DPI. Confocal microscopy revealed Flot-2 expression in neurons, reactive astrocytes and oligodendrocytes specifically associated to myelin structures near or close to the axons of the cord. In the open field test and grid walking assays, to monitor locomotor recovery of injured rats infused intrathecally with Flot-2 antisense oligonucleotides for 28 days showed significant behavioral improvement at 14, 21 and 28 DPI. These findings suggest that Flot-2 has a role in the non-permissive environment that blocks locomotor recovery after SCI by clustering unfavorable proteins in membrane rafts.
Membrane raft; trauma; lipid raft; regeneration; neurite outgrowth; locomotor recovery
We previously reported that anti-Aβ single-chain antibody (scFv59) brain delivery via recombinant adeno-associated virus (rAAV) was effective in reducing cerebral Aβ load in an AD mouse model without inducing inflammation. Here, we investigated the prophylactic effects and mechanism of a muscle-directed gene therapy modality in an AD mouse model. We injected rAAV serotype 1 encoding scFv59 into the right thigh muscles of 3-month-old mice. Nine months later, high levels of scFv59 expression were confirmed in the thigh muscles by both immunoblotting and immunohistochemistry. As controls, model mice were similarly injected with rAAV1 encoding anti-HIV Gag antibody (scFvGag). AAV1-mediated scFv59 gene delivery was effective in decreasing Aβ deposits in the brain. Compared with the scFvGag group, levels of Aβ in cerebrospinal fluid (CSF) decreased significantly while Aβ in serum tended to increase in the scFv59 group. AAV1-mediated scFv59 gene delivery may alter the equilibrium of Aβ between the blood and brain, resulting in an increased efflux of Aβ from the brain owing to antibody-mediated sequestration/clearance of peripheral Aβ. Our results suggest that muscle-directed scFv59 delivery via rAAV1 may be a prophylactic option for AD and that levels of CSF Aβ may be used to evaluate the efficacy of anti-Aβ immunotherapy.
single-chain antibody; adeno-associated virus; amyloid; Alzheimer’s disease; cerebrospinal fluid
Microtubule binding protein Tau has been implicated in a wide range of neurodegenerative disorders collectively classified as tauopathies. Exon 10 of the human tau gene, which codes for a microtubule binding repeat region, is alternatively spliced to form Tau protein isoforms containing either four or three microtubule binding repeats, Tau4R and Tau3R, respectively. The levels of different Tau splicing isoforms are fine-tuned by alternative splicing with the ratio of Tau4R/Tau3R maintained approximately at one in adult neurons. Mutations that disrupt tau exon 10 splicing regulation cause an imbalance of different tau splicing isoforms and have been associated with tauopathy. To search for factors interacting with tau pre-messenger RNA (pre-mRNA) and regulating tau exon 10 alternative splicing, we performed a yeast RNA–protein interaction screen and identified polypyrimidine tract binding protein associated splicing factor (PSF) as a candidate tau exon 10 splicing regulator. UV crosslinking experiments show that PSF binds to the stem-loop structure at the 5′ splice site downstream of tau exon 10. This PSF-interacting RNA element is distinct from known PSF binding sites previously identified in other genes. Overexpression of PSF promotes tau exon 10 exclusion, whereas down-regulation of the endogenous PSF facilitates exon 10 inclusion. Immunostaining shows that PSF is expressed in the human brain regions affected by tauopathy. Our data reveal a new player in tau exon 10 alternative splicing regulation and uncover a previously unknown mechanism of PSF in regulating tau pre-mRNA splicing.
Tau; Alternative splicing regulation; Tauopathy; RNA stem-loop secondary structure; Polypyrimidine tract binding protein associated splicing factor (PSF)
Oligomerization of G-protein-coupled receptors (GPCRs) is emerging as a mechanism for regulation and functional modification, although it has been studied most extensively for Family A receptors. Family B receptors have clear structural differences from Family A. In this paper, we have systematically evaluated GPCRs that are capable of association with the prototypic Family B secretin receptor. All of the receptor constructs were shown to traffic normally to the plasma membrane. We utilized receptor bioluminescence resonance energy transfer (BRET) to determine the presence of constitutive and ligand-dependent receptor association. Extensive intra-family and no cross-family association was observed. Of the nine Family B receptors studied, all constitutively yielded a significant BRET signal with the secretin receptor, except for the calcitonin receptor. Each of the associating hetero-oligomeric receptor pairs generated a BRET signal of similar intensity, less than that of homo-oligomeric secretin receptors. BRET signals from some receptor pairs were reduced by ligand occupation, but none were increased by this treatment. Thus, Family B GPCR oligomerization occurs, with many structurally related members associating with each other. The specific functional implications of this need to be further evaluated.
G-protein-coupled receptors; Heteroligomerization; Secretin receptor; Bioluminescence resonance energy transfer; Fluorescence resonance energy transfer; Surface expression
Synaptic plasticity in many regions of the central nervous system leads to the continuous adjustment of synaptic strength, which is essential for learning and memory. In this study, we show by visualizing synaptic vesicle release in mouse hippocampal synaptosomes that presynaptic mitochondria and specifically, their capacities for ATP production are essential determinants of synaptic vesicle exocytosis and its magnitude. Total internal reflection microscopy of FM1-43 loaded hippocampal synaptosomes showed that inhibition of mitochondrial oxidative phosphorylation reduces evoked synaptic release. This reduction was accompanied by a substantial drop in synaptosomal ATP levels. However, cytosolic calcium influx was not affected. Structural characterization of stimulated hippocampal synaptosomes revealed that higher total presynaptic mitochondrial volumes were consistently associated with higher levels of exocytosis. Thus, synaptic vesicle release is linked to the presynaptic ability to regenerate ATP, which itself is a utility of mitochondrial density and activity.
Prenatal alcohol exposure is known to induce fetal brain growth deficits at different embryonic stages. We focused this study on investigating the neuroprotective effects against alcohol-induced apoptosis at midgestation using activity-dependent neurotrophic factor (ADNF)-9, a peptide (SALLRSIPA) derived from activity-dependent neurotrophic factor, and NAP, a peptide (NAPVSIPQ) derived from activity-dependent neuroprotective protein. We used an established fetal alcohol exposure mouse model. On embryonic day 7 (E7), weight-matched pregnant females were assigned to the following groups: (1) ethanol liquid diet (ALC) group with 25 % (4.49 %, v/v) ethanol-derived calories, (2) pair-fed (PF) control group, (3) ALC combined with i.p. injections (1.5 mg/kg) of ADNF-9 (ALC/ADNF-9) group, (4) ALC combined with i.p. injections (1.5 mg/kg) of NAP (ALC/NAP) group, (5) PF liquid diet combined with i.p. injections of ADNF-9 (PF/ADNF-9) group, and (6) PF liquid diet combined with i.p. injections of NAP (PF/NAP) group. On day 15 (E15), fetal brains were collected, weighed, and assayed for TdT-mediated dUTP nick end labeling (TUNEL) staining. ADNF-9 or NAP was administered daily from E7 to E15 alongside PF or ALC liquid diet exposure. Our results show that NAP and ADNF-9 significantly prevented alcohol-induced weight reduction of fetal brains. Apoptosis was determined by TUNEL staining; NAP or ADNF-9 administration alongside alcohol exposure significantly prevented alcohol-induced increase in TUNEL-positive cells in primordium of the cingulate cortex and ganglionic eminence. These findings may pave the path toward potential therapeutics against alcohol intoxication during pregnancy stages.
Neuroprotection; Fetal alcohol syndrome; Fetal alcohol exposure; Prenatal alcohol exposure; TUNEL; Apoptosis
Current understanding of the molecular basis of activation of class II G protein-coupled receptors remains limited, despite recent solution of NMR and crystal structures of amino-terminal domains of several family members. One mechanism proposed for the activation of these receptors involves an agonist-stimulated change in conformation of the receptor amino terminus. This results in the exposure of a “hidden endogenous agonist” (WDN sequence in secretin and VPAC1 receptors) within the receptor amino terminus that interacts with the receptor core, thereby changing its conformation and exposing its G protein-binding region. The Asn in this WDN sequence is known to be glycosylated in both secretin and VPAC1 receptors, raising concern about whether this posttranslational modification might interfere with the proposed mechanism. Therefore, we prepared glycosylated forms of cyclic WDN and the longer cyclic peptide, LWDNM, and tested them for agonist activity at secretin and VPAC1 receptor-bearing cell lines. Both glycosylated peptides stimulated full cAMP responses in the cell lines. Clearly, glycosylation did not interfere with this mechanism and may actually facilitate the correct orientation of the pharmacophore of the endogenous agonist ligand. These data provide further evidence for this proposed mechanism for the activation of this family of receptors.
G protein-coupled receptors; Secretin receptor; VPAC1 receptor; Receptor activation; Glycosylation
FoxN4 (forkhead box N4), which is a transcription factor involved in developing spinal cord and spinal neurogenesis, implied important roles in the central nervous system (CNS). However, its expression and function in the adult CNS lesion are still unclear. In this study, we established a spinal cord injury (SCI) model in adult rats and investigated the expression of FoxN4 in the spinal cord. Western blot analysis revealed that FoxN4 was present in normal spinal cord. It gradually increased, peaked at day 3 after SCI, and then decreased during the following days. Immunohistochemistry further confirmed that FoxN4 was expressed at low levels in gray and white matters in normal condition and increased after SCI. Double immunofluorescence staining showed that FoxN4 is located on neurons and astrocytes, and FoxN4 expression was increased progressively in reactive astrocytes within the vicinity of the lesion, predominately in the white matter. In addition, almost all FoxN4-positive cells also expressed nestin or PCNA. Our data suggested that FoxN4 might play important roles in CNS pathophysiology after SCI.
FoxN4; Spinal cord injury; Astrocytes; PCNA
The signal transduction mechanisms of pituitary adenylate cyclase activating polypeptide (PACAP) were investigated in lung cancer cells. Previously, PACAP-27 addition to NCI-H838 cells increased phosphatidylinositol turnover and intracellular cAMP leading to proliferation of lung cancer cells. Also, PACAP receptors (PAC1) regulated the tyrosine phosphorylation of ERK, focal adhesion kinase and paxillin. In this communication the effects of PACAP on cytosolic Ca2+ and PYK-2 tyrosine phosphorylation were investigated. PACAP-27 increased cytosolic Ca2+ within seconds after addition to FURA-2 AM loaded NCI-H838 cells. The increase in cytosolic Ca2+ caused by PACAP was inhibited by PACAP (6–38) (PAC1 antagonist), U73122 (phospholipase C inhibitor) or BAPTA (calcium chelator), but not H89 (PKA inhibitor). PACAP-38 but not vasoactive intestinal peptide (VIP), addition to NCI-H838 or H1299 cells significantly increased the tyrosine phosphorylation of PYK-2 after 2 min. The increase in PYK-2 tyrosine phosphorylation caused by PACAP was inhibited by PACAP(6–38), U73122 or BAPTA, but not H89. The results suggest that PAC1 regulates PYK-2 tyrosine phosphorylation in a calcium-dependent manner.
Calcium influx is required for the pituitary adenylyl cyclase activating polypeptide (PACAP)-induced increase in guinea pig cardiac neuron sexcitability, noted as a change from a phasic to multiple action potential firing pattern. Intracellular recordings indicated that pretreatment with the nonselective cationic channel inhibitors, 2-aminoethoxydiphenylborate (2-APB), 1-[β-[3-(4-methoxyphenyl)propoxy]-4-methoxy-phenethyl]-1H-imidazole HCl (SKF 96365), and flufenamic acid (FFA) reduced the 20-nM PACAP-induced excitability increase. Additional experiments tested whether 2-APB, FFA, and SKF 96365 could suppress the increase in excitability by PACAP once it had developed. The increased action potential firing remained following application of 2-APB but was diminished by FFA. SKF 96365 transiently depressed the PACAP-induced excitability increase. A decrease and recovery of action potential amplitude paralleled the excitability shift. Since semiquantitative PCR indicated that cardiac neurons express TRPC subunit transcripts, we hypothesize that PACAP activates calcium-permeable, nonselective cationic channels, which possibly are members of the TRPC family. Our results are consistent with calcium influx being required for the initiation of the PACAP-induced increase in excitability, but suggest that it may not be required to sustain the peptide effect. The present results also demonstrate that non-selective cationic channel inhibitors could have other actions, which might contribute to the inhibition of the PACAP-induced excitability increase.
Parasympathetic neurons; Neuropeptide; TRPC channels; Semiquantitative PCR; Calcium influx
Members of the neurotrophin family, including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4/5 (NT-4/5), and other neurotrophic growth factors such as ciliary neurotrophic factor (CNTF) and artemin, regulate peripheral and central nervous system development and function. A subset of the neurotrophin-dependent pathways in the hypothalamus, brainstem, and spinal cord, and those that project via the sympathetic nervous system to peripheral metabolic tissues including brown and white adipose tissue (BAT and WAT), muscle and liver, regulate feeding, energy storage, and energy expenditure. We briefly review the role that neurotrophic growth factors play in energy balance, as regulators of neuronal survival and differentiation, neurogenesis, and circuit formation and function, and as inducers of critical gene products that control energy homeostasis.
Brain-Derived Neurotrophic Factor (BDNF); Corticotropin Releasing Hormone (CRH); Hypothalamus; Nerve Growth Factor (NGF); Neurotrophin; VGF
Migraine is a debilitating neurological disorder characterized by mild to severe headache that is often accompanied by aura and other neurological symptoms. Among proposed mechanisms, dilation of the dural vasculature especially the middle meningeal artery (MMA) has been implicated as one component underlying this disorder. Several regulatory peptides from trigeminal sensory and sphenopalatine postganglionic parasympathetic fibers innervating these vessels have been implicated in the process including pituitary adenylate cyclase-activating polypeptide (PACAP). Although PACAP has been well described as a potent dilator in many vascular beds, the effects of PACAP on the dural vasculature are unclear. In the current study, we examined the ability of PACAP to dilate MMAs that were isolated from rats and pressurized ex vivo. PACAP38 potently dilated pressurized MMAs with an EC50 of 1 pM. The PAC1 receptor antagonist, PACAP(6-38), abolished MMA dilation caused by picomolar concentrations of PACAP. In contrast, cerebellar arteries isolated from the brain surface were ~1,000-fold less sensitive to PACAP than MMAs. Although cerebellar arteries expressed transcripts for all three PACAP receptor subtypes (PAC1, VPAC1, and VPAC2 receptors) by RT-PCR analyses, MMA demonstrated only PAC1 and VPAC2 receptor expression. Further, multiple variants of the PAC1 receptor were identified in the MMA. The expression of PAC1 receptors and the high potency of PACAP to induce MMA vasodilation are consistent with their potential roles in the etiology of migraine.
Migraine; Vascular smooth muscle; Neurotransmitter; Pituitary adenylate cyclase-activating polypeptide (PACAP); Calcitonin gene-related peptide (CGRP)
These studies examined transcriptional and translational plasticity of three transient receptor potential (TRP) channels (TRPA1, TRPV1, TRPV4) with established neuronal and non-neuronal expression and functional roles in the lower urinary tract. Mechanosensor and nociceptor roles in either physiological or pathological lower urinary tract states have been suggested for TRPA1, TRPV1 and TRPV4. We have previously demonstrated neurochemical, organizational and functional plasticity in micturition reflex pathways following induction of urinary bladder inflammation using the antineoplastic agent, cyclophosphamide (CYP). More recently, we have characterized similar plasticity in micturition reflex pathways in a transgenic mouse model with chronic urothelial overexpression (OE) of nerve growth factor (NGF) and in a transgenic mouse model with deletion of vasoactive intestinal polypeptide (VIP). In addition, the micturition reflex undergoes postnatal maturation that may also reflect plasticity in urinary bladder TRP channel expression. Thus, we examined plasticity in urinary bladder TRP channel expression in diverse contexts using a combination of quantitative, real-time PCR and western blotting approaches. We demonstrate transcriptional and translational plasticity of urinary bladder TRPA1, TRPV1 and TRVP4 expression. Although the functional significance of urinary bladder TRP channel plasticity awaits further investigation, these studies demonstrate context-(inflammation, postnatal development, NGF-OE, VIP deletion) and tissue-dependent (urothelium + suburothelium, detrusor) plasticity.
TRPA1; TRPV1; TRPV4; cyclophosphamide; NGF; VIP
Chromogranin A (CgA) is a member of the granins, a family of acidic proteins found in abundance in (neuro)endocrine cells (e.g. in chromaffin cells) and in some tumors. Like other granins, CgA has a granulogenic role in secretory granule biogenesis and is stored in these organelles. CgA is partially processed differentially in various cell types to yield biologically active peptides, such as vasostatin, pancreastatin, catestatin and serpinins. In this review we describe the roles of CgA and several of its derived peptides. CgA, which is elevated in the blood of cancer patients, inhibits angiogenesis and exerts protective effects on the endothelial barrier function in tumors, thus affecting response to chemotherapy. Recent studies indicate that the serpinins promote cell survival and myocardial contractility and relaxation. Other peptides such as pancreastatin was found to have significant effects on inhibition of glucose stimulated insulin secretion and glucose up-take, induction of glycogenolysis in hepatocytes and inhibition of lipogenesis. In contrast, catestatin has opposite effects to that of pancreastatin in glucose metabolism and lipogenesis. Catestatin appears to also play a significant role in cardiac function, blood pressure regulation, and mutations in the catestatin domain of the CgA gene are associated with hypertension in humans.
Chromogranin A; catestatin; vasostatin; serpinin; cancer; hypertension; diabetes
The bovine chromaffin cell represents an ideal model for the study of cell signaling to gene expression by first messengers. An abundance of GPCR, ionotropic, and growth factor receptors are expressed on these cells, and they can be obtained and studied as an abundant highly enriched cell population: importantly, this is true of no other post-mitotic neuroendocrine or neuronal cell type. Chromaffin cells have now been shown to bear receptors for cytokines whose expression in the circulation is highly elevated in inflammation, including TNF, IFN, IL-1 and IL-6. The use of bovine-specific microarrays, and various biochemical measurements in this highly homogenous cell preparation, reveals unique cohorts of distinct genes regulated by cytokines in chromaffin cells, via signaling pathways that are in some cases uniquely neuroendocrine. The transcriptomic signatures of cytokine signaling in chromaffin cells suggest that the adrenal medulla may integrate neuronal, hormonal, and immune signaling during inflammation through induction of paracrine factors that signal to both adrenal cortex and sensory afferents of the adrenal gland, and autocrine factors, which determine the duration and type of paracrine secretory signaling that occurs in either acute or chronic inflammatory conditions.
adrenal medulla; chromaffin cell; cytokine; IFN; IL-1; IL-6; inflammation; PACAP; stress; TNF
Our recent studies have demonstrated that integrin-linked kinase (ILK) is involved in the induction and maintenance of cocaine behavioral sensitization and chronic cocaine-induced neural plasticity in the nucleus accumbens (NAc) core. In the present study, we used ILK silencing to investigate how ILK may influence cocaine-induced neural plasticity. Adeno-associated virus carrying a small interfering RNA-ILK cassette under the control of an inducible Tet-On system was injected into the NAc core of Sprague–Dawley rats. Induced silencing was established during repeated cocaine injections (sensitization induction period) or between withdrawal days 9 and 22 (sensitization maintenance period). Under both paradigms, established cocaine sensitization under non-silenced conditions was associated with enhanced PSD-95 and synapsin I protein expression as well as enhanced Ser845 phosphorylation of the GluR1 subunit on withdrawal day. Silencing ILK expression under both paradigms prevented or reversed these changes. Importantly, ILK appears to form a complex with PSD-95 and synapsin I because it co-immunoprecipitated with each of these proteins. Together, these data suggest that ILK exerts pleiotropic actions by regulating pre- and postsynaptic neural plasticities within the NAc core in response to repeated cocaine exposure.
Integrin-linked kinase; Cocaine; Behavioral sensitization; PSD-95; SiRNA; GluR1; Synapsin I; Synaptic plasticity
Frontotemporal lobar dementia (FTLD) is the most common cause of dementia in patients younger than 60 years of age, and causes progressive neurodegeneration of the frontal and temporal lobes usually accompanied by devastating changes in language or behavior in affected individuals. Mutations in the progranulin (GRN) gene account for a significant fraction of familial FTLD, and in the vast majority of cases, these mutations lead to reduced expression of progranulin via nonsense-mediated mRNA decay. Progranulin is a secreted glycoprotein that regulates a diverse range of cellular functions including cell proliferation, cell migration, and inflammation. Recent fundamental discoveries about progranulin biology, including the findings that sortilin and tumor necrosis factor receptor (TNFR) are high affinity progranulin receptors, are beginning to shed light on the mechanism(s) by which progranulin deficiency causes FTLD. This review will explore how alterations in basic cellular functions due to PGRN deficiency, both intrinsic and extrinsic to neurons, might lead to the development of FTLD.
Progranulin; Frontotemporal lobar dementia; Sortilin; Tumor necrosis factor receptor; TDP-43; Neuroinflammation
The hippocampus undergoes changes with aging that impact neuronal function, such as synapse loss and altered neurotransmitter release. Nearly half of the aged population also develops deficits in spatial learning and memory. To identify age-related hippocampal changes that may contribute to cognitive decline, transcriptomic analysis of synaptosome preparations from adult (12 months) and aged (28 months) Fischer 344-Brown Norway rats assessed for spatial learning and memory was performed. Bioinformatic analysis identified the MHCI pathway as significantly upregulated with aging. Age-related increases in mRNAs encoding the MHCI genes RT1-A1, RT1-A2, and RT1-A3 was confirmed by qPCR in synaptosomes and in CA1 and CA3 dissections. Elevated levels of the MHCI cofactor (B2m), antigen-loading components (Tap1, Tap2, Tapbp), and two known MHCI receptors (PirB, Klra2) were also confirmed. Protein expression of MHCI was elevated with aging in synaptosomes, CA1, and DG, while PirB protein expression was induced in both CA1 and DG. MHCI expression was localized to microglia and neuronal excitatory postsynaptic densities, and PirB localized to neuronal somata, axons and dendrites. Induction of the MHCI antigen processing and presentation pathway in hippocampal neurons and glia may contribute to age-related hippocampal dysfunction by increasing neuroimmune signaling or altering synaptic homeostasis.
aging; hippocampus; Major Histocompatibility Complex I; Paired Immunoglobulin-like Receptor B; synapse; neuroimmune
Huntingtin Associated Protein 1 (HAP1) is a binding partner for huntingtin, the protein responsible for Huntington’s Disease. In mammals, HAP1 is mostly found in brain where it is expressed in neurons. Although several functions have been proposed for HAP1, its role has not yet been clearly established. Here we report on the identification of a HAP1 C.elegans homolog called T27A3.1. T27A3.1 shows conservation with rat and human HAP1 as well as with Milton, a Drosophila HAP1 homolog. To determine the cellular expression of T27A3.1 (multiple isoforms; a-e), we generated several transgenic worm lines expressing a fluorescent reporter protein (GFP and DsRed2) or full length T27A3.1a/c isoforms fused to GFP under the control of the promoter for T27A3.1. We have found that T27A3.1 is expressed in many cell types including a subset of chemosensory neurons in the head and tail. These include the amphid chemosensory neurons ASKL and R, ASIL and R, ADFL and ASEL; the phasmid neurons PHBL and R; and the CAN neurons which are required for worm survival. Furthermore, we show that the subcellular localization of T27A3.1a/c resemble that of mammalian HAP1 and that T27A3.1a/c localize to stigmoid body like structures.
Huntington; localization; amphid; phasmid; stigmoid body
Alteration of the biological activity among neuronal components of the Mesocorticolimbic (MCL) system has been implicated in the pathophysiology of drug abuse. Changes in the electrophysiological properties of neurons involved in the reward circuit seem to be of utmost importance in addiction. The Hyperpolarization-Activated Cyclic-Nucleotide Current, Ih, is a prominent mixed cation current present in neurons. The biophysical properties of the Ih and its potential modulatory role in cell excitability depend on the expression profile of the Hyperpolarization-activated cyclic nucleotide gated channel (HCN) subunits. We investigated whether cocaine-induced behavioral sensitization, an animal model of drug addiction, elicits region-specific changes in the expression of the HCN2 channel’s subunit in the MCL system. Tissue samples from the ventral tegmental area, prefrontal cortex, nucleus accumbens and hippocampus were analyzed using Western Blot. Our findings demonstrate that cocaine treatment induced a significant increase in the expression profile of the HCN2 subunit in both, its glycosylated and non-glycosylated protein isoforms, in all areas tested. The increase in the glycosylated isoform was only observed in the ventral tegmental area. Together, these data suggest that the observed changes in MCL excitability during cocaine addiction might be associated to alterations in the subunit composition of their HCN channels.
addiction; cocaine sensitization; ventral tegmental area; accumbens; Ih current; HCN channels
Many experiments affirm the notion that augmentation of neurotrophic factors (NTFs) activity, especially brain-derived neurotrophic factors and glial cell-derived neurotrophic factors, could prevent or halt the progress of neurodegeneration in Parkinson’s disease (PD). In this study, we investigated the therapeutic accomplishment of geraniol (GE 100 mg/kg) on 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mice model of PD. Current investigation proved that pretreatment with GE ameliorates the MPTP-induced alterations in behavioral, biochemical, immunohistochemical, and immunoblotting manifestations in mice. Systematically, the loss of dopaminergic neurons and reduced NTFs mRNA expressions induced by MPTP was ameliorated to a significant extent by pretreatment with GE. We found that GE confers a potent neuroprotective agent against MPTP-induced dopaminergic denervation and may become a potential therapeutic agent for PD and/or its progression.
Neurotrophic factors; Neurodegeneration; Parkinson’s disease; Neuroprotective
Familial idiopathic basal ganglia calcification (FIBGC) is a neurodegenerative disorder with neuropsychiatric and motor symptoms. Deleterious mutations in SLC20A2, encoding the type III sodium-dependent phosphate transporter 2 (PiT2), were recently linked to FIBGC in almost 50 % of the families reported worldwide. Here, we show that knockout of Slc20a2 in mice causes calcifications in the thalamus, basal ganglia, and cortex, demonstrating that reduced PiT2 expression alone can cause brain calcifications.
SLC20A2; Brain calcification; Phosphate transporter; PiT2