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)

Various mechanisms have been identified by which hormones and neurotransmitters, interacting with heptahelical receptors, modulate the intracellular Ca2+ concentration in neuronal, endocrine, and neuroendocrine cells. All of them involve heterotrimeric G proteins. Best documented are hormonal stimulations and inhibitions of voltage-dependent Ca2+ channels. Stimulation is caused by agonists interacting with receptors known to induce phosphatidylinositol 4,5-bisphosphate hydrolysis, that is, a PI response. Although the PI response triggers a transient secretion by fast Ca2+ release, the stimulation of Ca2+ channels is assumed to be responsible for prolonged cell responses and for refilling of IP3-sensitive Ca2+ pools after repeated stimulations. Using antisense oligonucleotide microinjection in rat pituitary GH3 cells, Gi2 has been identified as the pertussis toxin-sensitive G protein stimulating Ca2+ channels, whereas Gq/G11 are involved in the concurrent PI response with subsequent protein kinase C activation, which is required for Ca2+ channel stimulation. Inhibitory modulations of Ca2+ channels are assumed to be the basis of inhibitions of transmitter or hormone secretion. Experiments in GH3 cells have revealed that Go subforms composed of alpha o1 x beta 3 x gamma 4 and alpha o2 x beta 1 x gamma 3 are the active G-protein heterotrimers transferring inhibitory signals from muscarinic M4 and somatostatin receptors to the Ca2+ channel, respectively.
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PMID:Heterotrimeric G proteins involved in the modulation of voltage-dependent calcium channels of neuroendocrine cells. 797 80

Activation of a calmodulin (CaM)-dependent protein kinase associated with rabbit skeletal-muscle sarcoplasmic reticulum (SR) results in the phosphorylation of polypeptides of 450, 360, 165, 105, 89, 60, 34 and 20 kDa. Radioligand-binding studies indicated that a membrane-bound 60 kDa polypeptide contained both CaM- and ATP-binding domains. Under renaturing conditions on nitrocellulose blots, the 60 kDa polypeptide of the membrane exhibited CaM-dependent autophosphorylation activity, suggesting that it was the CaM-dependent protein kinase of SR. Ca2+/CaM-independent autophosphorylation of polypeptides of 62 and 45 kDa was found to occur in the light SR, whereas the Ca2+/CaM-dependent autophosphorylation activity was enriched in the heavy SR. Both these kinase activities were absent from transverse tubules, although these membranes were enriched in CaM-binding polypeptides of 160, 100 and 80 kDa. In the absence of Ca2+, CaM bound to a 33 kDa polypeptide of the membrane. The purified ryanodine receptor was not phosphorylated by the purified CaM kinase, although it was a substrate for protein kinase C. Affinity-purified antibodies to brain CaM kinase II cross-reacted with the 60 kDa polypeptide in Western blots and immunoprecipitated the 60 kDa polypeptide, along with the 360, 105, 89, 34 and 20 kDa phosphoproteins, from Nonidet-P-40-solubilized SR membranes. Antibodies raised against the 60 kDa kinase polypeptide did not cross-react with the other phosphoproteins, suggesting that these polypeptides were distinct and unrelated. Subcellular distribution of the 60 kDa kinase indicated the specific association of the polypeptide with the junctional-face membrane of SR. The CaM-dependent incorporation of 32P into various membrane proteins was inhibited by the CaM kinase II fragment (290-309), with an IC50 value of 2 nM for the inhibition of incorporation into the 60 kDa kinase polypeptide. Recent studies [Wang and Best (1992) Nature (London) 359, 739-741] have shown that a CaM kinase activity intrinsic to the membrane can inactivate the Ca(2+)-release channel of skeletal muscle SR. Since our results demonstrate that the 60 kDa polypeptide of SR is a CaM-dependent protein kinase, we suggest that this kinase, through its associations, may be responsible for gating the Ca(2+)-release channel.
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PMID:A 60 kDa polypeptide of skeletal-muscle sarcoplasmic reticulum is a calmodulin-dependent protein kinase that associates with and phosphorylates several membrane proteins. 824 Mar 1

Obesity is commonly associated with elevated plasma levels of free fatty acids (FFAs). High levels of FFA have emerged as a major link between obesity and insulin resistance/type 2 diabetes (T2DM). Thus, acute and chronic elevations of plasma FFAs produce insulin resistance in skeletal muscle and liver. In skeletal muscle, FFA-induced insulin resistance is associated with accumulation of intramyocellular triglyceride and diacylglycerol, and with activation of protein kinase C (the beta and delta isoforms). It is suggested that FFAs interfere with insulin signalling via PKC-induced serine phosphorylation of the insulin receptor substrate-1. In the liver, FFAs cause insulin resistance by interfering with insulin suppression of glycogenolysis. In beta-cells, FFAs potentiate glucose-stimulated insulin secretion acutely and chronically. It is postulated that this prevents the development of T2DM in most (>80%) obese insulin-resistant people who have FFA-mediated insulin resistance. Elevated levels of FFA also seem to activate a pro-inflammatory and pro-atherogenic pathway (the IkappaB/NFkappaB pathway) and may be responsible, at least in part, for the increase in atherosclerotic vascular disease seen in patients with T2DM. As increased plasma levels account for up to 50% of insulin resistance in obese patients with T2DM, lowering of plasma FFAs could be a new and promising approach to the treatment of T2DM.
Best Pract Res Clin Endocrinol Metab 2003 Sep
PMID:Nutritional effects of fat on carbohydrate metabolism. 1296 93

Myelodysplastic syndrome (MDS) is a heterogeneous group of clonal hematopoietic disorders. Therapeutic interventions for MDS other than allogeneic bone marrow transplantation have been palliative. Because most of the patients are elderly and may not be candidates for ablative transplant conditioning regimens, treatment has focused on supportive care. Recently, several novel biological and chemotherapeutic agents have demonstrated activity in MDS and are being incorporated into the treatment paradigm. These agents are based on specific mechanisms aimed at angiogenesis in the bone marrow, secretion of growth factors and/or their receptors, and modulators in their intracellular pathways. Several agents are in the initial stages of clinical trial, including anti-vascular endothelial growth factor, bevacizumab, receptor tyrosine kinase inhibitors, farnesyl transferase inhibitors, protein kinase C inhibitors, matrix metalloproteinase inhibitors and other agents such as thalidomide and arsenic trioxide. Novel chemotherapeutic agents include topoisomerase inhibitors such as topotecan and rubitecan, and deoxyadenosine analogues such as troxacitabine, tezacitabine, and clofarabine. Prognostic factors predicting response in MDS patients treated with intensive chemotherapy have been identified and include younger age and favorable cytogenetics.
Best Pract Res Clin Haematol 2004 Dec
PMID:Nucleoside analogs and antimetabolite therapies for myelodysplastic syndrome. 1549 95

Treatment of myelodysplastic syndrome (MDS) has been hampered by the lack of understanding of the molecular and biological abnormalities associated with this disease. Biological abnormalities may lead to typical phenotypic changes in more differentiated cells. Recent developments in the natural history and underlying molecular mechanisms of MDS and acute myeloid leukemia (AML) have identified new molecular therapeutic targets. Several new classes of drugs have shown promise in early clinical trials and may alter the standard of care of these patients. Among these new drugs are farnesyltransferase inhibitors, receptor tyrosine kinase inhibitors, protein kinase C inhibitors, and VEGF inhibitors. These agents have been tested in patients with solid tumors and hematological malignancies such as AML and MDS. Most of the studies in MDS are in early stages of development, where doses are being determined based on the experience in refractory or relapsed AML or solid tumors. Future therapies in MDS will attempt to resolve cytopenias, eliminate malignant clones and allow differentiation by attacking specific mechanisms of the disease.
Best Pract Res Clin Haematol 2004 Dec
PMID:Inhibitors of signaling in myelodysplastic syndrome. 1549 98

Current investigations have revealed that angiogenesis plays a role in the pathogenesis of high-risk myelodysplastic syndrome (MDS) and acute myeloid leukemia, and in the mechanisms of disease progression. Secretion of cytokines and growth factors modulates angiogenesis in the marrow leading to increased vascularity and sustenance of the clonal population. For high-risk MDS patients older than 60 years who are not eligible for aggressive chemotherapy or stem cell transplant, there are few therapeutic options other than supportive treatment. Recent delineation of the pathobiology of MDS has resulted in the development of new agents and treatment modalities that impact on these mechanisms. One of the features of bone marrow pathology is the presence of new vessels, which appear to sustain growth and the hypercellularity of the marrow. Blocking angiogenesis may reduce the microvessel density of the marrow, cellularity, and disease progression. Angiogenesis can be targeted by inhibition of vascular endothelial growth factor (VEGF), which modulates new vessel growth, by the use of antibodies aimed at VEGF and its receptors, as well as receptor tyrosine kinases that block VEGF signaling. Other agents include inhibitors of farnesyl transferase and protein kinase C, which affect upstream modulators of growth factors and their receptor interactions; matrix metalloproteinases, which disrupt matrices and adhesion function promoting vessel growth; and other inhibitors with broader function, such as endostatin, thalidomide, and related analogues.
Best Pract Res Clin Haematol 2004 Dec
PMID:Modulation of angiogenesis in patients with myelodysplastic syndrome. 1549 99

Regulated intramembrane proteolysis (RIP) represents an evolutionarily conserved process linking receptor function with transcriptional regulation. Best characterized by the Notch signaling pathway, RIP involves regulated ectodomain shedding followed by gamma-secretase-mediated release of the C-terminal, cytosolic domain. The C-terminus in turn translocates to the nucleus where it interacts with other proteins to regulate expression of specific genes. Recent studies in our laboratory have shown that megalin, a scavenger receptor in proximal tubule, is subjected to RIP in a manner very similar to that of Notch. We showed that megalin in subjected to protein kinase C-regulated, metalloprotease-mediated ectodomain shedding producing a membrane-associated C-terminal fragment (MCTF). The MCTF in turn forms the substrate for gamma-secretase. These data implicate megalin as a central element of a Notch-like signaling pathway linking protein reabsorption and gene regulation in proximal tubule. The likelihood that megalin processing plays an important role in the progression of proteinuric kidney disease is discussed.
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PMID:Regulated intramembrane proteolysis of megalin: linking urinary protein and gene regulation in proximal tubule? 1655 31

In patients with diabetes, the hyperglycaemia is known to promote high levels of diacylglycerol which activates protein kinase C (PKC) in the vascular tissues and leads to production of vascular endothelial growth factor (VEGF) in the retina. PKC activation is likely to play a key role in diabetic microvascular complications, particularly changes in vascular permeability and ischaemia in the retina. A new potential therapeutic agent, the PKC-beta inhibitor ruboxistaurin, has been studied in animal and human clinical trials in diabetic microvascular disease, particularly in patients with diabetic retinopathy. The mechanism of action of PKC and the results of these trials are discussed in this review. Ruboxistaurin shows promise as an oral treatment for diabetic retinopathy. The trials have demonstrated a significant reduction in visual loss and need for laser treatment in patients with moderate to severe diabetic retinopathy over a 3-year period. There have been no significant concerns over safety or the side-effects profile in the clinical trials. Ruboxistaurin currently has approvable status pending further randomized trials defined by the US Food and Drug Administration (FDA).
Best Pract Res Clin Endocrinol Metab 2007 Dec
PMID:PKC inhibition and diabetic microvascular complications. 1805 36

Best vitelliform macular dystrophy is an inherited autosomal dominant, juvenile onset form of macular degeneration caused by mutations in a chloride ion channel, human bestrophin-1 (hBest1). Mutations in Best1 have also been linked to several other forms of retinopathy. In addition to mutations, hBest1 dysfunction might come about by disruption of other processes that regulate Best1 function. Here we show that hBest1 chloride channel activity is regulated by ceramide and phosphorylation. We have identified a protein kinase C (PKC) phosphorylation site (serine 358) in hBest1 that is important for sustained channel function. Channel activity is maintained by PKC activators, protein phosphatase inhibitors, or pseudo-phosphorylation by substitution of glutamic acid for serine 358. When ceramide levels are elevated by exogenous addition of ceramide to the bath, by addition of bacterial sphingomyelinase, or by hypertonic stress, S358 is rapidly dephosphorylated. The dephosphorylation is mediated by protein phosphatase 2A. Hypertonic stress-induced dephosphorylation is blocked by a dihydroceramide, an inactive form of ceramide, and manumycin, an inhibitor of neutral sphingomyelinase. Our results support a model in which ceramide accumulation during early stages of retinopathy inhibits hBest1 function, leading to abnormal fluid transport across the retina, and enhanced inflammation.
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PMID:Dysregulation of human bestrophin-1 by ceramide-induced dephosphorylation. 1963 17