Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

IA-2, a member of the protein tyrosine phosphatase family, represents a major target autoantigen in type 1 diabetes. To study the regulation of IA-2 gene expression, we used INS-1 insulinoma cells to analyze beta-cell signal transduction pathways as well as the effect of metabolic and hormonal factors involved in the regulation of the insulin secretory pathway. Quantitative competitive reverse transcriptase-polymerase chain reaction revealed that an increase of cellular cAMP mediated by forskolin (10 micromol/l, 24 h) or 3-isobutyl-1-methylxanthine (100 micromol/l, 24 h) induced maximal stimulation of IA-2 mRNA levels (451 +/- 85 and 338 +/- 86% compared with basal conditions; P < 0.001). In contrast, activation of protein kinase C (PKC) by short-term treatment with phorbol 12-myristate 13-acetate (PMA) (1 micromol/l, 6 h) did not alter IA-2 expression, whereas depletion of PKC by prolonged culturing (24 h) exerted a significant inhibition (57 +/- 24%; P < 0.05). cAMP-dependent upregulation was confirmed by the findings that glucagon (10 micromol/l, 24-48 h) increased levels of IA-2 mRNA (190 +/- 35%; P < 0.05), whereas short-term incubation with high glucose concentration showed no effect. However, prolonged incubation in high glucose (21 mmol/l) induced a time- and dose-dependent increase of IA-2 mRNA expression, reaching maximal values after 144 h (285 +/- 68%; P < 0.05). These studies demonstrate that stimuli of insulin secretion that operate by activation of adenylate cyclase generating cAMP significantly increase IA-2 gene expression. In contrast, activation of PKC by high glucose concentration or PMA exerted no effect, suggesting that IA-2 gene expression is not simply coupled to insulin secretion, but may be involved in the fine regulation of beta-cell function. These findings may be important to clarify the function of IA-2 in beta-cells and elucidate mechanisms involved in the induction of autoimmunity to IA-2.
 ...
PMID:Regulation of the diabetes-associated autoantigen IA-2 in INS-1 pancreatic beta-cells. 1090 70

Isolated pancreatic islets from rat and mouse and the insulinoma cell lines, betaHC9 and RINm5F, were investigated to determine the regulation of metallothionein (MT). Dexamethasone (DEX) increased rat and mouse islet and insulinoma cell MT levels in a time- and concentration-dependent manner. Rat islet MT expression was increased with interleukin-1beta (IL-1beta), but not tumor necrosis factor-alpha (TNF). However, MT induction by IL-1beta and TNF was synergistic with DEX in rat islets and insulinoma cells. Mouse islet MT failed to respond to IL-1beta alone, although IL-1beta and TNF were synergistic. IL-1beta and TNF did not synergize with DEX for mouse islet MT induction. Zinc sulfate induced MT in rat islets but not mouse islets. MT messenger RNA levels were significantly increased in rat islets in response to DEX and IL-1beta plus DEX. The inducible nitric oxide synthase inhibitors N(G)-monomethyl-L-arginine and aminoguanidine failed to inhibit IL-1beta induced MT levels in insulinoma cells, and the nitric oxide generating agent sodium nitroprusside failed to significantly affect MT levels. Phorbol dibutyrate increased MT levels in rat islets and betaHC9 cells, but phorbol dibutyrate and IL-1beta effects were not additive. Transgenic MT-null and wild-type mouse islets had similar insulin contents, but basal and glucose-stimulated insulin release from MT-null islets were significantly lower than in wild-type islets. Blood glucose levels in MT-null mice were, however, slightly lower than those in wild-type mice. Thus, MT induction in pancreatic islets and beta-cells is regulated by cytokines and DEX, and protein kinase C activation may play a role. However, regulation of MT induction in mouse and rat islets differs. MT also appears to modulate insulin release from pancreatic islets.
 ...
PMID:Metallothionein induction in islets of Langerhans and insulinoma cells. 1094 Apr 96

GH and PRL stimulate proliferation and insulin production of pancreatic beta-cells. Whereas GH- and PRL-regulated transcription of the insulin gene in insulinoma cells has been shown to depend on STAT5 (signal transducer and activator of transcription 5), the signaling pathways involved in GH/PRL-induced beta-cell replication are unknown. The roles of various signaling pathways in human GH (hGH)-induced DNA synthesis were studied by analysis of the effect of specific inhibitors in both the insulin-producing cell line, INS-1, and in primary beta-cells. The mitogen-activated protein kinase kinase (MEK)-inhibitor, PD98059, as well as the mitogen-activated protein kinase p38 (MAPKp38) inhibitor, SB203580, partially inhibited hGH- induced proliferation in INS-1 cells but had no significant effect in primary beta-cells. Staurosporine, a protein kinase C (PKC) and protein kinase A (PKA) inhibitor, blocked both basal and hGH-induced proliferation in INS-1 cells, but had no inhibitory effect in primary beta-cells. Wortmannin, a phosphatidylinositol 3-kinase (PI3K) inhibitor, inhibited hGH-induced proliferation neither in INS-1 cells nor in primary beta-cells, whereas the tyrosine kinase inhibitor, genistein, completely inhibited hGH- induced proliferation in both primary beta-cells and INS-1 cells. To analyze the possible role of STAT5 in hGH-induced proliferation, a dominant negative STAT5 mutant, STAT5Delta749, was expressed in INS-1 cells under the control of a doxycycline- inducible promoter by stable transfection. Two clones were found to exhibit dose-dependent, doxycycline-inducible expression of STAT5Delta749 and suppression of hGH-stimulated transcriptional activation of a STAT5-regulated PRL receptor (PRLR) promoter-reporter construct. Furthermore, induction of STAT5Delta749 expression completely inhibited hGH-induced DNA synthesis. Analysis of endogenous gene expression revealed a doxycycline-dependent inhibition of hGH-stimulated PRLR and cyclin D2 mRNA levels. Our results suggest that GH/PRL-induced beta-cell proliferation is dependent on the Janus Kinase2 (JAK2)/STAT5 signaling pathway but not the MAPK, PI3K, and PKC signaling pathways. Furthermore, the cell cycle regulator cyclin D2 may be a crucial target gene for STAT5 in this process.
 ...
PMID:Growth hormone- and prolactin-induced proliferation of insulinoma cells, INS-1, depends on activation of STAT5 (signal transducer and activator of transcription 5). 1114 45

Reversible protein phosphorylation is an important and versatile mechanism by which cells transduce external signals into biological responses. Cellular levels of protein phosphorylation are determined by the balanced actions of both protein kinases and protein phosphatases (PPases). Compared with protein kinases, however, serine/threonine PPases have received less attention. In the present study, the effects of certain insulin secretagogues and intracellular second messengers, known to stimulate or inhibit insulin secretion, on the activities of cation-independent serine/threonine PPases were investigated in insulin-secreting RINm5F insulinoma cells. Raising cellular cAMP through adenylyl cyclase activation and phosphodiesterase inhibition in intact cells, evoked inhibitory effects on PPase activities. The addition of a nitric oxide donor, cyclic nucleotides, or proinflammatory prostaglandins to RINm5F cell homogenates at widely different concentrations did not affect type-1 or -2A PPase activities. Phosphatidyl serine seemingly activated PPase-1, while inactivating PPase-2A. A protein kinase C-activating phorbol ester produced the opposite results when added to RINm5F cell homogenates. These studies suggest that several known intracellular second messengers are without effect on beta-cell PPase activities. However, phosphatidyl serine and protein kinase C activation, whose activity is transiently increased by glucose, may promote insulin release through PPase inactivation, likely contributing to the increase in phosphorylation state that occurs after stimulation of insulin release. Thus, inhibition of protein dephosphorylation may be a novel regulatory mechanism, assisting in activation of the stimulus-secretion coupling in insulin-producing cells.
 ...
PMID:Effects of second messengers on serine/threonine protein phosphatases in insulin-secreting cells. 1132 9

Voltage-gated K(+) channel alpha subunits (K(V) alpha) have been previously identified in pancreatic islet beta-cells where it has been suggested they have a role in membrane repolarization and insulin secretion. Here we report the cloning of the three mammalian K(V) beta subunits, including splice variants of these subunits, from both human and rat pancreatic islets and from the rat insulinoma cell line INS-1. Two of the splice variants, K(V) beta1a and K(V) beta3, previously reported to be neuronal tissue specific, are expressed in islets and INS-1 cells. In addition, a splice variant of K(V) beta2 that lacks two potential protein kinase C phosphorylation sites at the amino terminus is present. Immunoblot analysis suggests a high level of K(V) beta2 subunit protein in rat pancreatic islets and immunoprecipitation with anti-K(V) beta2 antibody pulls down a protein from INS-1 cells that reacts with anti-aldose reductase antibody. The K(V) beta subunits, which are attached to the cytoplasmic face of the alpha subunits and are members of the aldose reductase superfamily of NADPH oxidoreductases, may have an as yet undetermined role in the regulation of insulin secretion by the intracellular redox potential. Finally, we suggest that a systematic nomenclature for K(V) beta subunits first proposed by McCormack et al. be adopted for this family of potassium channel subunits as it corresponds with the nomenclature used for their cognate K(V) alpha subunits.
 ...
PMID:Evidence for voltage-gated potassium channel beta-subunits with oxidoreductase motifs in human and rodent pancreatic beta cells. 1134 91

The role of the different isoforms of protein kinase C (PKC) in modulating insulin secretion is still widely unknown. The aim of our studies was to investigate which isoforms are influenced by gastrin-releasing peptide (GRP), a neuropeptide which has been shown to modulate insulin secretion by activating PKC. Presence of PKC isoforms alpha, beta, gamma, delta, epsilon and zeta was tested by immunoblot analysis in whole pancreatic islets of mouse and rat and in the insulinoma cell line RINm5F. Effects of GRP, the truncated peptide GRP1-16 and KCl were also measured on translocation of PKC isoforms. In pancreatic islets of mouse and rat, the PKC isoforms alpha, beta, gamma, delta, epsilon and zeta could be detected. No PKCgamma activity was present in the pancreatic tumor cell line RINm5F. Incubation of mouse or rat islets or of RINm5F cells with GRP induced translocation of the PKC isoforms alpha, beta and zeta. The N-terminal portion of the peptide GRP1-16 induced partial translocation only of the PKC isoforms alpha, beta and zeta in mouse and rat islets in 4 out of 10 cases, but failed to show any effect on PKC isoforms in RINm5F cells. Depolarization of the islets by KCl did not translocate any tested PKC isoform. However, incubation with GRP followed by depolarization with KCl led to translocation of the PKC isoforms alpha, beta and zeta. It is suggested that PKC alpha, beta and/or zeta may play a role in the modulation of insulin secretion by GRP.
 ...
PMID:Distribution and stimulation by gastrin-releasing peptide of protein kinase C subfamilies in insulin-secreting cells. 1139 8

A cytosolic 84 kDa Group VIA phospholipase A2 (iPLA2beta) that does not require Ca2+ for catalysis was cloned from Chinese hamster ovary (CHO) cells, murine P388D1 cells, pancreatic islet beta-cells, and other sources. Proposed iPLA2beta functions include participation in phosphatidylcholine (PC) homeostasis by degrading excess PC generated in CHO cells that overexpress CTP:phosphocholine cytidylyltransferase (CT), which catalyzes the rate-limiting step in PC biosynthesis; participation in biosynthesis of arachidonate-containing PC species in P388D1 cells by generating lysophosphatidylcholine (LPC) acceptors for arachidonate incorporation; and participation in signaling events in insulin secretion from islet beta-cells. To further examine iPLA2beta functions in beta-cells, we prepared stably transfected INS-1 insulinoma cell lines that overexpress iPLA2beta activity eightfold compared to parental INS-1 cells or to INS-1 cells transfected with an empty retroviral vector that did not contain iPLA2beta cDNA. The iPLA2beta-overexpressing cells exhibit a twofold increase in CT activity compared to parental cells but little change in rates of [3H]choline incorporation into or disappearance from PC. Electrospray ionization (ESI) tandem mass spectrometric measurements indicate that iPLA2beta-overexpressing cells have 1.5-fold higher LPC levels than parental INS-1 cells but do not exhibit increased rates of [3H]arachidonate incorporation into phospholipids, and incorporation is unaffected by a bromoenol lactone (BEL) suicide substrate inhibitor of iPLA2beta. The rate of appearance of arachidonate-containing phosphatidylethanolamine species visualized by ESI mass spectrometry is also similar in iPLA2beta-overexpressing and parental INS-1 cells incubated with supplemental arachidonic acid, and this process is unaffected by BEL. Compared to parental INS-1 cells, iPLA2beta-overexpressing cells proliferate more rapidly and exhibit amplified insulin secretory responses to a protein kinase C-activating phorbol ester, glucose, and a cAMP analog. These findings suggest that iPLA2beta plays a signaling role in beta-cells that differs from housekeeping functions in PC biosynthesis and degradation in P388D1 and CHO cells.
 ...
PMID:Studies of phospholipid metabolism, proliferation, and secretion of stably transfected insulinoma cells that overexpress group VIA phospholipase A2. 1152 67

The tSNARE (the target-membrane soluble NSF-attachment protein receptor, where NSF is N -ethylmaleimide-sensitive fusion protein) synaptosomal-associated protein of 25 kDa (SNAP-25) is implicated in regulated insulin secretion. In pheochromocytoma PC12 cells, SNAP-25 is phosphorylated at Ser(187), which lies in a region that is important for its function. The aims of the present study were to determine whether SNAP-25 is phosphorylated at Ser(187) in insulin-secreting cells and, if so, whether this is important for regulated insulin secretion. The major findings are: (i) SNAP-25 is rapidly and reversibly phosphorylated on Ser(187) in both rat insulinoma INS-1 cells and rat islets in response to the phorbol ester, PMA; (ii) less than 35% of SNAP-25 in INS-1 cells is phosphorylated in response to PMA, and phosphorylation is limited to plasma-membrane-associated SNAP-25; (iii) both SNAP-25 isoforms (a and b) are phosphorylated, with 1.8-fold greater phosphorylation for SNAP-25b in response to PMA; (iv) in rat islets, Ser(187) phosphorylation is stimulated by glucose or carbachol, albeit to a lesser extent than by PMA, but not by cAMP; (v) insulin secretion from botulinum neurotoxin E-treated hamster insulinoma tumour (HIT) cells, transfected with toxin-resistant Ser(187)-->Ala or Ser(187)-->Asp mutant SNAP-25, was similar to that of wild-type HIT cells. Furthermore, in rat islets no correlation was found between the extent of SNAP-25 phosphorylation at Ser(187) in response to secretagogues and stimulation of insulin release; (vi) use of protein kinase C (PKC) inhibitors suggests that glucose stimulates SNAP-25 phosphorylation via conventional and non-conventional PKC isoforms. In summary, although SNAP-25 phosphorylation at Ser(187) occurs in insulin-secreting cells and is mediated by PKC, it does not appear to play a major role in regulated insulin secretion.
 ...
PMID:Phosphorylation of SNAP-25 on serine-187 is induced by secretagogues in insulin-secreting cells, but is not correlated with insulin secretion. 1216 83

Antagonism of voltage-dependent K+ (Kv) currents in pancreatic beta-cells may contribute to the ability of glucagon-like peptide-1 (GLP-1) to stimulate insulin secretion. The mechanism and signaling pathway regulating these currents in rat beta-cells were investigated using the GLP-1 receptor agonist exendin 4. Inhibition of Kv currents resulted from a 20-mV leftward shift in the voltage dependence of steady-state inactivation. Blocking cAMP or protein kinase A (PKA) signaling (Rp-cAMP and H-89, respectively) prevented the inhibition of currents by exendin 4. However, direct activation of this pathway alone by intracellular dialysis of cAMP or the PKA catalytic subunit (cPKA) could not inhibit currents, implicating a role for alternative signaling pathways. A number of phosphorylation sites associated with phosphatidylinositol 3 (PI3)-kinase activation were up-regulated in GLP-1-treated MIN6 insulinoma cells, and the PI3 kinase inhibitor wortmannin could prevent antagonism of beta-cell currents by exendin 4. Antagonists of Src family kinases (PP1) and the epidermal growth factor (EGF) receptor (AG1478) also prevented current inhibition by exendin 4, demonstrating a role for Src kinase-mediated trans-activation of the EGF tyrosine kinase receptor. Accordingly, the EGF receptor agonist betacellulin could replicate the effects of exendin 4 in the presence of elevated intracellular cAMP. Downstream, the PKCzeta pseudosubstrate inhibitor could prevent current inhibition by exendin 4. Therefore, antagonism of beta-cell Kv currents by GLP-1 receptor activation requires both cAMP/PKA and PI3 kinase/PKCzeta signaling via trans-activation of the EGF receptor. This represents a novel dual pathway for the control of Kv currents by G protein-coupled receptors.
 ...
PMID:Antagonism of rat beta-cell voltage-dependent K+ currents by exendin 4 requires dual activation of the cAMP/protein kinase A and phosphatidylinositol 3-kinase signaling pathways. 1456 57

During the last decade significant advances in gene therapy have made it possible to treat various pancreatic disorders in both animal models and in humans. For example, insulin gene delivery to non-beta-cell tissues has been shown to reverse hyperglycemia in diabetic mice, and islet transplantation, based on in vitro differentiation of beta cells and concomitant gene targeting to prevent host autoimmune responses, has become more feasible. Additionally, introduction of the glucokinase regulatory protein and protein kinase C-zeta have been shown to improve glucose tolerance in non-insulin-dependent diabetes mellitus animal models. Pancreatic cancer studies utilize several DNA-based strategies for tumor treatment including introduction of tumor suppressor genes, suppression of oncogenes, suicide gene/prodrug therapy, and restricted replication-competent virus therapy. Tumor-specific targeting is an important part of suicide gene therapy, and tumor-specific promoters are used for cell-specific targeting. Tumor-specific suicide gene therapy directed by the rat insulin promoter has been used to eliminate insulinoma tumors in a mouse model. This review compiles a compendium of information related to the treatment of pancreatic disorders using gene therapy.
 ...
PMID:Molecular targeting of pancreatic disorders. 1589 36


<< Previous 1 2 3 4 5 Next >>