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

Proteins of the ras family of oncogenes have been implicated in signal transduction pathways initiated by protein kinase C (PKC) and by tyrosine kinase oncogenes and receptors, but the role that ras plays in these diverse signalling systems is poorly defined. The activity of ras proteins has been shown to be controlled in part by a cellular protein, GAP (GTPase-activating protein), that negatively regulates p21c-ras by enhancing its intrinsic GTPase activity. Thus, overexpression of GAP provides a tool for determining the step(s) in signal transduction dependent on p21c-ras activity. In this paper, we report that overexpression of GAP blocks the phorbol ester (tetradecanoyl phorbol acetate [TPA])-induced activation of p42 mitogen-activated protein kinase (p42mapk), c-fos expression, and DNA synthesis. GAP overexpression did not block responses to serum or fluoroaluminate. Moreover, not all biochemical events elicited by TPA were affected by GAP overexpression, as increased glucose uptake and phosphorylation of MARCKS, a major PKC substrate, occurred normally. Reduction of GAP expression to near normal levels restored the ability of the cells to activate p42mapk in response to TPA. These findings suggest that ras and GAP together play a key role in a PKC-dependent signal transduction pathway which leads to p42mapk activation and cell proliferation.
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PMID:Regulation of tetradecanoyl phorbol acetate-induced responses in NIH 3T3 cells by GAP, the GTPase-activating protein associated with p21c-ras. 154 25

T cell stimulation via the TCR complex (TCR/CD3 complex) results in activation of the guanine nucleotide binding proteins encoded by the ras protooncogenes (p21ras). In the present study we show that the activation state of p21ras in T lymphocytes can also be controlled by triggering of the CD2 Ag. The activation state of p21ras is controlled by GTP levels on p21ras. In T cells stimulation of protein kinase C is able to induce an accumulation of "active" p21ras-GTP complexes due to an inhibitory effect of protein kinase C stimulation on the intrinsic GTPase activity of p21ras. The regulatory effect of protein kinase C on p21ras GTPase activity appears to be mediated via regulation of GAP, the GTPase activating protein of p21ras. In the present report, we demonstrate that the TCR/CD3 complex and the CD2 Ag control the accumulation of p21ras-GTP complexes via a regulatory effect on p21ras GTPase activity. The TCR/CD3 complex and CD2 Ag are also able to control the cellular activity of GAP. These data demonstrate that p21ras is part of the signal transduction responses controlled by the CD2 Ag, and reveal that the TCR/CD3 complex and CD2 Ag control the activation state of p21ras via a similar mechanism.
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PMID:CD2 antigen mediated activation of the guanine nucleotide binding proteins p21ras in human T lymphocytes. 167 18

The interaction of the brain-specific calmodulin-binding protein kinase C (PKC) substrate, neuromodulin (GAP 43), with membrane phospholipids was studied. Specific binding of neuromodulin to negatively charged phospholipids through electrostatic interactions was demonstrated. Comparison of the binding of neuromodulin to acidic phospholipids with that of neurogranin, a newly characterized calmodulin-binding PKC substrate (Baudier J., Deloulme, J. C., Van Dorsselaer, A., Black, D., and Mathes H. (1991) J. Biol. Chem. 266, 229-237) suggested that the conserved basic amino acid sequence which characterizes the two proteins and which corresponds to the PKC phosphorylation and calmodulin binding domain also serves as phospholipid binding site. In the absence of calmodulin, binding of neuromodulin to phosphatidylserine at low concentration parallels its phosphorylation by PKC, suggesting that formation of a ternary complex between neuromodulin, phosphatidylserine, and PKC is required for optimum neuromodulin phosphorylation. In the presence of calmodulin, the binding of neuromodulin to phosphatidylserine is inhibited, resulting in total inhibition of neuromodulin phosphorylation. Our results suggest that, in vivo, phosphorylation of neuromodulin may not only depend on protein kinase C (PKC)1 activation but also on the accessibility of the neuromodulin phosphorylation domain to activated membrane-bound PKC that could regulated by CaM.
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PMID:The interactions of the brain-specific calmodulin-binding protein kinase C substrate, neuromodulin (GAP 43), with membrane phospholipids. 182 85

GAP-43, a major protein of neuronal growth cones and certain presynaptic terminals, is a candidate for important functions in both axon growth and synaptic plasticity. To facilitate studies that may elucidate these functions, we have efficiently generated large quantities of GAP-43 by introducing a GAP-43 cDNA into a bacterial expression system driven by T7-RNA polymerase. Two constructs were expressed in this system: one (pT7Ava-GAP) produces a fusion protein in which the first 16 amino acids of GAP-43 are replaced by 11 amino acids of the phage T7 capsid protein; the other (pT7FL-GAP) produces full length GAP-43. After the bacteria were lysed, both products were soluble, and could be efficiently purified by HPLC chromatography on a C4 reversed-phase column. One liter of bacterial culture yielded 50 mg of purified fusion protein or 10 mg of complete GAP-43. When it was incubated with protein kinase C, the fusion protein was phosphorylated at the same single site (serine 41) that is phosphorylated in cultured neurons. The ability to produce large quantities of GAP-43 by this procedure should expedite future studies investigating its structure, posttranslational modification, and function.
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PMID:Production of the neuronal growth-associated protein GAP-43 in a bacterial expression system. 183 54

We report the cloning and expression of a cDNA encoding a high molecular weight (85.2 kd) cytosolic phospholipase A2 (cPLA2) that has no detectable sequence homology with the secreted forms of PLA2. We show that cPLA2 selectively cleaves arachidonic acid from natural membrane vesicles and demonstrate that cPLA2 translocates to membrane vesicles in response to physiologically relevant changes in free calcium. Moreover, we demonstrate that an amino-terminal 140 amino acid fragment of cPLA2 translocates to natural membrane vesicles in a Ca(2+)-dependent fashion. Interestingly, we note that this 140 amino acid domain of cPLA2 contains a 45 amino acid region with homology to PKC, p65, GAP, and PLC. We suggest that this homology delineates a Ca(2+)-dependent phospholipid-binding motif, providing a mechanism for the second messenger Ca2+ to translocate and activate cytosolic proteins.
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PMID:A novel arachidonic acid-selective cytosolic PLA2 contains a Ca(2+)-dependent translocation domain with homology to PKC and GAP. 190 18

Oncogenic forms of p21ras are found in a wide range of human tumors. However, the mechanism by which p21ras transforms remains obscure. Genetic evidence has identified a domain of p21ras that is involved with interaction with an effector molecule required for transformation. Two proteins, GAP and the tumor suppressor NF1, interact with p21ras in this region but it is an unresolved puzzle whether either of these is the an unresolved puzzle whether either of these is the effector. After interaction with an effector, two downstream events--activation of protein kinase C and another pathway--are necessary for induction of DNA synthesis by oncogenic p21ras; however, morphological transformation does not require activation of protein kinase C.
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PMID:How does p21ras transform cells? 203 Dec 88

External signals that control the activity of proteins encoded by the ras proto-oncogenes have not previously been characterized. It is now shown that stimulation of the antigen receptor of T lymphocytes causes a rapid activation of p21ras. The mechanism seems to involve a decrease in the activity of GAP, the GTPase-activating protein, on stimulation of protein kinase C. In lymphocytes, p21ras may therefore be an important mediator of the action of protein kinase C.
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PMID:Stimulation of p21ras upon T-cell activation. 220 20

To study the role of protein kinase C (PKC) and its substrates in neuronal function, we have investigated the in vitro endogenous phosphorylation of the neuronal phosphoprotein F1 after induction of synaptic plasticity by long-term potentiation (LTP). The protein F1 phosphorylation was found to increase 5 min (Routtenberg et al., 1985), 1 hr (Lovinger et al., 1986) and 3 d (Lovinger et al., 1985) after LTP. The characteristics of this protein bear close similarities to a number of proteins characterized in various neuronal systems, such as B50 (brain specific, synaptosome-enriched protein), pp46 (a growth cone protein), and GAP 43 (nerve growth and regeneration-associated protein). A positive identification of the purified protein F1 with these proteins would link protein F1 to the developmental growth of axons, nerve regeneration, and polyphosphoinositide metabolism, as well as adult plasticity. We have therefore purified and partially characterized native protein F1 so that a meaningful comparison among the properties of these proteins can be made. Using synaptosomal plasma membrane (P2') as starting material, subsequent purification involved pH extraction, 40-80% ammonium sulfate precipitation, hydroxylapatite, and phenyl-Sepharose column chromatography. This procedure achieved greater than 800-fold purification and about 45% yield relative to P2'. Purified protein F1 (Mr = 47,000, pI = 4.5) was found to be a hydrophilic molecule and was phosphorylated by 1000-fold purified PKC in the presence of phosphatidylserine (PS) and Ca2+. The Ka of PS activation is about 15 micrograms/ml (approximately 20 microM), and that of Ca2+ is about 25 microM. Diolein and DiC:8 (a synthetic diacylglycerol) lowered the requirement of Ca2+ for maximal stimulation from 100 to 5 microM. Ca2+-calmodulin kinases type I and II did not phosphorylate protein F1. The phosphoamino acid analysis showed that 97% of the total incorporated 32P-phosphate was on the serine residue. Phosphopeptide mapping using V8-protease generated 2 phospho-fragments having apparent Mr of 13,000 and 11,000. Calmodulin at 3.6 microM inhibited 95% of protein F1 phosphorylation by PKC. The availability of purified native protein F1 should facilitate investigation of the physiological role of this protein in the nervous system and its functional regulation by PKC.
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PMID:Phosphoprotein F1: purification and characterization of a brain kinase C substrate related to plasticity. 379 93

p120 GAP is a GTPase activating protein for p21 ras. It is a multidomain protein which exhibits sequence similarity with other GTPase-activating proteins, src, pleckstrin and a central portion of the protein kinase C conserved region 2 domain known as CaLB (Ca(2+)-dependent phospholipid-binding). The presence of this CaLB motif has led to the speculation that p120 GAP may be a member of a family of structurally related proteins containing a Ca(2+)-dependent membrane/lipid-binding domain. Here we have studied the in vitro Ca(2+)-dependent phospholipid-binding properties of the isolated proposed CaLB sequence in human GAP and deduce that a phospholipid-binding sequence is indeed located between amino acids 606 and 648. Binding of phosphatidylserine and phosphatidylinositol, but not phosphatidylcholine, within this sequence is Ca(2+)-dependent, with an estimated EC50 for Ca2+ of approx. 1 microM. Using deletion-mutation analysis we have further defined the minimal boundaries for this in vitro phospholipid-binding activity. p120 GAP amino acids 612-643 exhibit full phospholipid-binding activity, but further deletion of either amino acids 612-617 or amino acids 633-648 significantly decreased or abolished phospholipid binding. These studies establish that amino acids 612-643 of p120 GAP indeed constitute a functional CaLB domain and thereby imply a role for Ca2+ in the regulation of p120 GAP association with cellular (membrane) phospholipids.
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PMID:Mutation-deletion analysis of a Ca(2+)-dependent phospholipid binding (CaLB) domain within p120 GAP, a GTPase-activating protein for p21 ras. 773 87

Long-term potentiation (LTP) is a well known experimental model for studying the activity-dependent enhancement of synaptic plasticity, and because of its long duration and its associative properties, it has been proposed as a system to investigate the molecular mechanisms of memory formation. At present, there are several lines of evidence that indicate that pre- and postsynaptic kinases and their specific substrates are involved in molecular mechanisms underlying LTP. Many studies focus on the involvement of protein kinase C (PKC). One way to investigate the role of PKC in long-term potentiation is to determine the degree of phosphorylation of its substrates after in situ phosphorylation in hippocampal slices. Two possible targets are the presynaptic membrane-associated protein B-50 (a.k.a. GAP 43, neuromodulin and F1), which has been implicated in different forms of synaptical plasticity in the brain such as neurite outgrowth, hippocampal LTP and neurotransmitter release, and the postsynaptic protein neurogranin (a.k.a. RC3, BICKS and p17) which function remains to be determined. This review will focus on the protein kinase C activity in pre- and postsynaptic compartment during the early phase of LTP and the possible involvement of its substrates B-50 and neurogranin.
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PMID:Long-term potentiation and synaptic protein phosphorylation. 775 99


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