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1.  Diabetes, pancreatic cancer, and metformin therapy 
Pancreatic cancer carries a poor prognosis as most patients present with advanced disease and preferred chemotherapy regimens offer only modest effects on survival. Risk factors include smoking, obesity, heavy alcohol, and chronic pancreatitis. Pancreatic cancer has a complex relationship with diabetes, as diabetes can be both a risk factor for pancreatic cancer and a result of pancreatic cancer. Insulin, insulin-like growth factor-1 (IGF-1), and certain hormones play an important role in promoting neoplasia in diabetics. Metformin appears to reduce risk for pancreatic cancer and improve survival in diabetics with pancreatic cancer primarily by decreasing insulin/IGF signaling, disrupting mitochondrial respiration, and inhibiting the mammalian target of rapamycin (mTOR) pathway. Other potential anti-tumorigenic effects of metformin include the ability to downregulate specificity protein transcription factors and associated genes, alter microRNAs, decrease cancer stem cell proliferation, and reduce DNA damage and inflammation. Here, we review the most recent knowledge on risk factors and treatment of pancreatic cancer and the relationship between diabetes, pancreatic cancer, and metformin as a potential therapy.
PMCID: PMC4224068  PMID: 25426078
metformin; pancreatic cancer; diabetes; mTOR; AMPK; insulin; IGF-1
2.  Effects of Oxidative Alcohol Metabolism on the Mitochondrial Permeability Transition Pore and Necrosis in a Mouse Model of Alcoholic Pancreatitis 
Gastroenterology  2012;144(2):10.1053/j.gastro.2012.10.037.
Opening of the mitochondrial permeability transition pore (MPTP) causes loss of the mitochondrial membrane potential (ΔΨm) and, ultimately, adenosine triphosphate depletion and necrosis. Cells deficient in cyclophilin D (CypD), a component of the MPTP, are resistant to MPTP opening, loss of ΔΨm, and necrosis. Alcohol abuse is a major risk factor for pancreatitis and is believed to sensitize the pancreas to stressors, by poorly understood mechanisms. We investigated the effects of ethanol on the pancreatic MPTP, the mechanisms of these effects, and their role in pancreatitis.
We measured ΔΨm in mouse pancreatic acinar cells incubated with ethanol alone and in combination with physiologic and pathologic concentrations of cholecystokinin-8 (CCK). To examine the role of MPTP, we used ex vivo and in vivo models of pancreatitis, induced in wild-type and CypD−/− mice by a combination of ethanol and CCK.
Ethanol reduced basal ΔΨm and converted a transient depolarization, induced by physiologic concentrations of CCK, into a sustained decrease in ΔΨm, resulting in reduced cellular adenosine triphosphate and increased necrosis. The effects of ethanol and CCK were mediated by MPTP because they were not observed in CypD−/− acinar cells. Ethanol and CCK activated MPTP through different mechanisms— ethanol by reducing the ratio of oxidized nicotinamide adenine dinucleotide to reduced nicotinamide adenine dinucleotide, as a result of oxidative metabolism, and CCK by increasing cytosolic Ca2+. CypD−/− mice developed a less-severe form of pancreatitis after administration of ethanol and CCK.
Oxidative metabolism of ethanol sensitizes pancreatic mitochondria to activate MPTP, leading to mitochondrial failure; this makes the pancreas susceptible to necrotizing pancreatitis.
PMCID: PMC3841074  PMID: 23103769
Tissue Damage; Ethanol Toxicity; Cell Death; Exocrine Pancreas
3.  Genes, Tolerance and Systemic Autoimmunity 
Autoimmunity Reviews  2011;11(9):664-669.
The characterization of functional CD8+ inhibitory or regulatory T cells and their gene regulation remains a critical challenge in the field of tolerance and autoimmunity. Investigating the genes induced in regulatory cells and the regulatory networks and pathways that underlie mechanisms of immune resistance and prevent apoptosis in the CD8+ T cell compartment are crucial to understanding tolerance mechanisms in systemic autoimmunity. Little is currently known about the genetic control that governs the ability of CD8+ Ti or regulatory cells to suppress anti-DNA Ab production in B cells. Silencing genes with siRNA or shRNA and overexpression of genes with lentiviral cDNA transduction are established approaches to identifying and understanding the function of candidate genes in tolerance and immunity. Elucidation of interactions between genes and proteins, and their synergistic effects in establishing cell-cell cross talk, including receptor modulation/antagonism, are essential for delineating the roles of these cells. In this review, we will examine recent reports which describe the modulation of cells from lupus prone mice or lupus patients to confer anti-inflammatory and protective gene expression and novel associated phenotypes. We will highlight recent findings on the role of selected genes induced by peptide tolerance in CD8+ Ti.
PMCID: PMC3306516  PMID: 22155015
Autoimmunity; Systemic Lupus Erythematosus; CD8+ Treg; Genes and Tolerance
4.  Differential PKC-dependent and -independent PKD activation by G protein α subunits of the Gq family: selective stimulation of PKD Ser748 autophosphorylation by Gαq 
Cellular Signalling  2011;24(4):914-921.
Protein kinase D (PKD) is activated within cells by stimulation of multiple G protein coupled receptors (GPCR). Earlier studies demonstrated a role for PKC to mediate rapid activation loop phosphorylation-dependent PKD activation. Subsequently, a novel PKC-independent pathway in response to Gαq-coupled GPCR stimulation was identified. Here, we examined further the specificity and PKC-dependence of PKD activation using COS-7 cells cotransfected with different Gq-family Gα and stimulated with aluminum fluoride (AlF4−). PKD activation was measured by kinase assays, and Western blot analysis of activation loop sites Ser744, a prominent and rapid PKC transphosphorylation site, and Ser748, a site autophosphorylated in the absence of PKC signaling. Treatment with AlF4− potently induced PKD activation and Ser744 and Ser748 phosphorylation, in the presence of cotransfected Gαq, Gα11, Gα14 or Gα15. These treatments achieved PKD activation loop phosphorylation similar to the maximal levels obtained by stimulation with the phorbol ester, PDBu. Preincubation with the PKC inhibitor GF1 potently blocked Gα11-, Gα14-, and Gα15-mediated enhancement of Ser748 phosphorylation induced by AlF4−, and largely abolished Ser744 phosphorylation. In contrast, Ser748 phosphorylation was almost completely intact, and Ser744 phosphorylation was significantly activated in cells cotransfected with Gαq. Importantly, the differential Ser748 phosphorylation was also promoted by treatment of Swiss 3T3 cells with Pasteurella multocida toxin, a selective activator of Gαq but not Gα11. Taken together, our results suggest that Gαq, but not the closely related Gα11, promotes PKD activation in response to GPCR ligands in a unique manner leading to PKD autophosphorylation at Ser748.
PMCID: PMC3286641  PMID: 22227248
5.  Drinking and driving pancreatitis 
Autophagy  2011;7(7):783-785.
Alcohol abuse is the leading etiologic factor of pancreatitis, although many heavy drinkers do not develop pancreatic damage. Alcohol promotes pancreatitis through a combination of remote (e.g., increased gut permeability to bacterial products such as lipopolysaccharide) and more proximal effects (e.g., altered pancreatic cholinergic inputs), including oxidative damage at the level of the pancreatic acinar cell. Recent evidence indicates that alcohol exposure to rodents disturbs proteostasis in the exocrine pancreas, an effect counterbalanced by homeostatic processes that include both the unfolded protein response (UPR) and autophagy. A corollary to this notion is that pancreatitis results when adaptive responses are insufficiently robust to alleviate the cellular stress caused by alcohol.
PMCID: PMC3359467  PMID: 21460613
acinar cell; alcohol abuse; pancreas; ERAD; UPR; XBP1
6.  CID755673 enhances mitogenic signaling by phorbol esters, bombesin and EGF through a protein kinase D-independent pathway 
Recently, CID755673 was reported to act as a highly selective inhibitor of protein kinase D (PKD). In the course of experiments using CID755673, we noticed that it exerted unexpected stimulatory effects on [3H]thymidine incorporation and cell cycle progression in Swiss 3T3 cells stimulated by bombesin, a Gq-coupled receptor agonist, phorbol 12,13-dibutyrate (PDBu), a biologically active tumor promoting phorbol ester and epidermal growth factor (EGF). These stimulatory effects could be dissociated from the inhibitory effect of CID755673 on PKD activity, since enhancement of DNA synthesis was still evident in cells with severely down-regulated PKD1 after transfection of siRNA targeting PKD1. A major point raised by our study is that CID755673 can not be considered a specific inhibitor of PKD and it should be used with great caution in experiments attempting to elucidate the role of PKD family members in cellular regulation, particularly cell cycle progression from G1/Go to S phase.
PMCID: PMC2812606  PMID: 19896460
Swiss 3T3 cells; PDGF; PKD knock down; cell cycle; DNA synthesis
7.  Identification of a novel phosphorylation site in c-jun directly targeted in vitro by protein kinase D 
Protein kinase D (PKD) phosphorylates the c-jun amino-terminal in vitro at site(s) distinct from JNK [C. Hurd, R.T. Waldron, E. Rozengurt, Protein kinase D complexes with c-jun N-terminal kinase via activation loop phosphorylation and phosphorylates the c-jun N-terminus, Oncogene 21 (2002) 2154-2160], but the sites have not been identified. Here, metabolic 32P-labeling of c-jun protein in COS-7 cells indicated that PKD phosphorylates c-jun in vivo at a site(s) between aa 43-93, a region containing important functional elements. On this basis, the PKD-mediated phosphorylation site(s) was further characterized in vitro using GST-c-jun fusion proteins. PKD did not incorporate phosphate into Ser63 and Ser73, the JNK sites in GST-c-jun(1-89). Rather, PKD and JNK could sequentially phosphorylate distinct site(s) simultaneously. By mass spectrometry of tryptic phosphopeptides, Ser58 interposed between the JNK-binding portion of the delta domain and the adjacent TAD1 was identified as a prominent site phosphorylated in vitro by PKD. These data were further supported by kinase reactions using truncations or point-mutations of GST-c-jun. Together, these data suggest that PKD-mediated phosphorylation modulates c-jun at the level of its N-terminal functional domains.
PMCID: PMC2765859  PMID: 17359934
Protein kinase D; Protein kinase C; PKCmu; c-jun; c-jun N-terminal kinase; AP-1; Phosphorylation site; Activation loop; Phosphopeptide; Mass spectrometry
8.  The RAS Effector RIN1 Directly Competes with RAF and Is Regulated by 14-3-3 Proteins 
Molecular and Cellular Biology  2002;22(3):916-926.
Activation of RAS proteins can lead to multiple outcomes by virtue of regulated signal traffic through alternate effector pathways. We demonstrate that the RAS effector protein RIN1 binds to activated RAS with an affinity (Kd, 22 nM) similar to that observed for RAF1. At concentrations close to their equilibrium dissociation constant values, RIN1 and RAF1 compete directly for RAS binding. RIN1 was also observed to inhibit cellular transformation by activated mutant RAS. This distinguishes RIN1 from other RAS effectors, which are transformation enhancing. Blockade of transformation was mediated by the RAS binding domain but required membrane localization. RIN1 recognizes endogenous RAS following transient activation by epidermal growth factor, and a portion of RIN1 fractionates to the cell membrane in a manner consistent with a reversible interaction. RIN1 also binds to 14-3-3 proteins through a sequence including serine 351. Mutation of this residue abolished the 14-3-3 binding capacity of RIN1 and led to more efficient blockade of RAS-mediated transformation. The mutant protein, RIN1S351A, showed a shift in localization to the plasma membrane. Serine 351 is a substrate for protein kinase D (PKD [also known as PKCμ]) in vitro and in vivo. These data suggest that the normal localization and function of RIN1, as well as its ability to compete with RAF, are regulated in part by 14-3-3 binding, which in turn is controlled by PKD phosphorylation.
PMCID: PMC133556  PMID: 11784866

Results 1-8 (8)