Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cytoplasmic regions of the receptors for epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) bind and activate phospholipase C-gamma1 (PLC-gamma1) and other signaling proteins in response to ligand binding outside the cell. Receptor binding by PLC-gamma1 is a function of its SH2 domains and is required for growth factor-induced cell cycle progression into the S phase. Microinjection into MDCK epithelial cells and NIH 3T3 fibroblasts of a polypeptide corresponding to the noncatalytic SH2-SH2-SH3 domains of PLC-gamma1 (PLC-gamma1 SH2-SH2-SH3) blocked growth factor-induced S-phase entry. Treatment of cells with diacylglycerol (DAG) or DAG and microinjected inositol-1,4,5-triphosphate (IP3), the products of activated PLC-gamma1, did not stimulate cellular DNA synthesis by themselves but did suppress the inhibitory effects of the PLC-gamma1 SH2-SH2-SH3 polypeptide but not the cell cycle block imposed by inhibition of the adapter protein Grb2 or p21 Ras. Two c-fos serum response element (SRE)-chloramphenicol acetyltransferase (CAT) reporter plasmids, a wild-type version, wtSRE-CAT, and a mutant, pm18, were used to investigate the function of PLC-gamma1 in EGF- and PDGF-induced mitogenesis. wtSRE-CAT responds to both protein kinase C (PKC)-dependent and -independent signals, while the mutant, pm18, responds only to PKC-independent signals. Microinjection of the dominant-negative PLC-gamma1 SH2-SH2-SH3 polypeptide greatly reduced the responses of wtSRE-CAT to EGF stimulation in MDCK cells and to PDGF stimulation in NIH 3T3 cells but had no effect on the responses of mutant pm18. These results indicate that in addition to Grb2-mediated activation of Ras, PLC-gamma1-mediated DAG production is required for EGF- and PDGF-induced S-phase entry and gene expression, possibly through activation of PKC.
Mol Cell Biol 1998 Jan
PMID:Requirement for phospholipase C-gamma1 enzymatic activity in growth factor-induced mitogenesis. 941 5

To investigate the receptor-channel coupling pathway, the coding region of the 5-HT1a receptor was subcloned into two plasmid vectors pSP64(polyA+) and pSP64T. Compared to the original 5-HT1a receptor construct G-21, both new constructs increased greatly the expression of functional 5-HT1a receptors in Xenopus oocytes, which developed large inward current responses to 5-HT. These responses were dose-dependent (EC50 approximately 150 nM), and could be elicited also by 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). The 5-HT1a receptor mediated current had an oscillatory time course, and a reversal potential close to the equilibrium potential for Cl- (ca. -25 mV). Moreover, during and for some minutes following the application of 5-HT, these oocytes acquired the property of generating a transient inward current when their membrane was hyperpolarized. These features are characteristic of responses mediated by other receptors (e.g. muscarinic, angiotensin, serum receptors, etc.) that are known to couple to the endogenous PLC/PI second messenger pathway in Xenopus oocytes. In particular, the 5-HT1a receptor mediated current was very similar to the current induced by 5-HT-stimulation of heterogenic 5-HT2c receptors. Our results show further that the 5-HT1a receptor couples to the endogenous PLC/PI pathway much less efficiently than the 5-HT2c receptor. These results demonstrate clearly that the human 5-HT1a receptor can couple efficiently to the Xenopus oocyte endogenous PLC/PI pathway, and provide additional evidence for cell-specific signal transduction.
Brain Res Mol Brain Res 1997 Nov
PMID:Efficient coupling of 5-HT1a receptors to the phospholipase C pathway in Xenopus oocytes. 942 13

BKS-2 is an immature B cell lymphoma that undergoes apoptotic cell death when signaled via its surface IgM receptor. To study the signaling components of surface IgM mediated apoptosis in B lymphoma cells, we generated mutants of BKS-2 that were resistant to anti-IgM induced apoptosis. One mutant cell line, 1.B5, did not undergo apoptotic cell death upon treatment with anti-IgM antibodies and also did not exhibit elevation of intracellular Ca2+ in response to cross-linking of surface IgM. This appeared to be due to a defect in protein tyrosine kinase (PTK) activity since fewer proteins were tyrosine phosphorylated in the mutant cells stimulated with anti-IgM when compared to wild type BKS-2. Subsequently, we showed that protein tyrosine kinases lyn and blk were inducibly tyrosine phosphorylated in the wild type BKS-2 but not in 1.B5 mutant cells in response to anti-IgM. Also the kinase activity of lyn was elevated in the wild type but not in mutant cells upon triggering through surface IgM. Furthermore, tyrosine phosphorylation of CD19, a known substrate of lyn, was inducible in anti-IgM stimulated BKS-2 cells but severely reduced in 1.B5 cells. In contrast, kinase activity of another src kinase, blk, was increased on anti-IgM stimulation in both wild type and mutant cells. Surprisingly, syk, a non-src protein tyrosine kinase important for surface IgM mediated signaling, was tyrosine phosphorylated in the lyn deficient mutant cells as well as in the wild type BKS-2 cells. Furthermore, anti-IgM induced increase in kinase activity of syk was similar in the mutant and wild type cells. Thus, in contrast to other studies that propose syk to be a downstream target of src family kinases, syk may act upstream of lyn in immature B cells. Consistent with a functional syk, its target, phospholipase gamma2 (PLC-gamma2) was normally tyrosine phosphorylated in mutant cells.
Mol Immunol
PMID:Activation of syk in an immature B cell line does not require lyn activity. 946 22

The glycosylphosphatidylinositol phospholipase C (GPI-PLC) from Trypanosoma brucei is particularly effective in hydrolysing the GPI-anchors of some proteins. The enzyme is inhibited by Zn2+ and p-chloromercurylphenylsulphonic acid, both of which can act as sulphydryl reagents, suggesting that a cysteine residue may be important in catalysis. Single cysteine to serine mutants have been produced for all eight cysteines in GPI-PLC; all the mutants were fully active in vitro and were still susceptible to p-chloromercurylphenylsulphonic acid inhibition. In contrast, a single histidine 34 to glutamine mutation totally inactivated GPI-PLC. The histidine was chosen after a sequence alignment with the Bacillus cereus phosphatidylinositol phospholipase C (PI-PLC) suggested a conservation of active site residues, including histidine 34 which is central to the proposed reaction mechanism (Heinz D.W., Ryan M., Bullock T.L., Griffith O.H. EMBO J 1995;14:3855-3863). The results suggest that the GPI-PLC and bacterial PI-PLCs have conserved active sites and that the inhibition of GPI-PLC by sulphydryl reagents can occur through more than one residue.
Mol Biochem Parasitol 1997 Dec 15
PMID:Mutagenesis study of the glycosylphosphatidylinositol phospholipase C of Trypanosoma brucei. 947 90

The presence and role of the c-kit protein was investigated in the mature sperm of the mouse. The c-kit monoclonal antibody (mAb) ACK2 reacted specifically with the acrosomal region and the principal piece of fixed noncapacitated sperm but did not react with the acrosome region in acrosome-reacted sperm. ACK2 significantly inhibited the acrosome reaction; this inhibition was relieved by the calcium ionophore A23187. The kit ligand stem cell factor (SCF) significantly increased the percentage of sperm undergoing acrosome reaction. This increase was partially inhibited by the calcium channel inhibitor (verapamil), the PI3k inhibitor (wortmannin), and the PLC inhibitor (U-73122). ACK2 predominantly recognized c-kit proteins of 33, 48, and 150 kDa by Western blotting of mouse sperm extracts. The 48- and 150-kDa protein bands were released into the media and tyrosine autophosphorylated at low basal levels during acrosome reaction. On stimulation with SCF, the level of c-kit phosphorylation increased significantly. These findings suggest that c-kit is present in mature sperm, and its binding to SCF may result in the activation of PLC gamma 1 and PI3K, leading to receptor autophosphorylation, and ultimately may play a role in capacitation and/or the acrosome reaction.
Mol Reprod Dev 1998 Mar
PMID:The c-kit receptor and its possible signaling transduction pathway in mouse spermatozoa. 949 84

Activation of the delta-opioid receptor in NG108-15 neuroblastoma X glioma hybrid cells results in a transient increase at the intracellular level of inositol-1,4,5-triphosphate [Ins(1,4,5)P3]. This time course in the transient increase in the Ins(1,4,5)P3 level is distinctly different from that observed in the homologous opioid receptor desensitization as measured by the inhibition of adenylyl cyclase activity. One probable mechanism for this rapid loss in Ins(1,4,5)P3 response is the feedback regulation of the phospholipase C activity. Regulation by protein phosphorylation was suggested by the observations that the opioid-mediated response was potentiated by calphostin C, an inhibitor of protein kinase C (PKC), and was abolished by either phorbol-12-myristate-13-acetate, a PKC activator, or calyculin A, a protein phosphatase1/2A inhibitor. The direct phosphorylation of phospholipase C was demonstrated by immunoprecipitation of PLC-beta3 from metabolically labeled NG108-15 cells challenged with the delta-selective agonist [D-Pen2, D-Pen5]enkephalin (DPDPE). A time- and DPDPE concentration-dependent and naloxone-reversible increase in the PLC-beta3 phosphorylation can be demonstrated. This PLC-beta3 phosphorylation was mainly due to PKC activation because pretreatment of NG108-15 cells with calphostin C could block the DPDPE effect. Activation of the PLC-beta3 by DPDPE was one of the prerequisites for agonist-mediated PLC-beta3 phosphorylation because the aminosteroid phospholipase C inhibitor U73122 could block the DPDPE effect. In addition to DPDPE, lysophosphatidic acid (LPA) stimulated the PLC-beta3 phosphorylation, but bradykinin did not. Furthermore, the LPA- and DPDPE-mediated PLC-beta3 phosphorylation was additive and was much less than that observed with phorbol-12-myristate-13-acetate. The effect of DPDPE was specific to PLC-beta3; the betagamma-insensitive phospholipase C-beta1 was not phosphorylated in the presence of either DPDPE or LPA. These results indicate that although PKC phosphorylation of PLC-beta3 is not obligatory for the opioid receptor desensitization, it seems to play a significant facilatory role in the mechanisms allowing desensitization of opioid-activated phospholipase C response before that of adenylyl cyclase inhibition.
Mol Pharmacol 1998 Jun
PMID:Contribution of phospholipase C-beta3 phosphorylation to the rapid attenuation of opioid-activated phosphoinositide response. 961 7

Phosphoinositide (PI) 3-kinases, which phosphorylate the D-3 position of the inositol ring, function in several different signalling pathways. The phosphatidylinositol (PtdIns)-specific PI 3-kinase of yeast (Vps34p) is part of a receptor signalling protein complex associated with the trans-Golgi membranes, whereas PI 3-kinases that phosphorylate polyphosphoinositides in animal cells form a major receptor-controlled signalling pathway in the plasma membrane. Recent studies have indicated the presence of active PLC, PLD, and PI 3-kinase-dependent signalling systems in the unicellular green alga Chlamydomonas, and PtdIns-3P in Chlamydomonas shows a particularly high rate of turnover. Here we report the cloning of the Chlamydomonas Vps34p, and some characterisation of its properties, regulation and localisation. A single-copy 12 kb gene was present. The corresponding protein of 122 kDa had full-length homology with Vps34ps from other species, but it contained a novel spacer-like insert region of 148 amino acid residues between homology region 2 (HR2) and the C-terminal catalytic core domain, and three other shorter putative inserts. Available cDNAs were used to assemble a pBluescript clone expressing a recombinant protein which had PtdIns-specific 3-kinase activity. However, an unexpected observation was that recombinant proteins containing the complete catalytic core, but lacking HR2, had no lipid kinase activity, pointing to a previously unsuspected role for this domain, possibly in substrate binding. VPS34 mRNA and protein levels, as determined by RNAse protection assays and by immunological methods respectively, were low in all cell stages that were examined. Western blotting of subcellular fractions revealed that most of Vps34p in cell lysates of cw-15 (a cell wall-deficient mutant) could be recovered in a NP-40-resistant 100000 x g pellet, suggesting that the enzyme may have a location different from that found in higher plants.
Plant Mol Biol 1998 May
PMID:Inositide signalling in Chlamydomonas: characterization of a phosphatidylinositol 3-kinase gene. 962 Feb 64

Earlier autoradiographic studies from our laboratory detected vasopressin recognition sites in the mammalian cerebral cortex [R.E. Brinton, K.W. Gee, J.K. Wamsley, T.P. Davis, H.I. Yamamura, Regional distribution of putative vasopressin receptors in rat brain and pituitary by quantitative autoradiography, Proc. Natl. Acad. Sci. U. S.A., 81 (1984) 7248-7252; C. Chen, R.D. Brinton, T.J. Shors, R.F. Thompson, Vasopressin induction of long-lasting potentiation of synaptic transmission in the dentate gyrus, Hippocampus, 3 (1993) 193-204]. More recently, we have detected mRNA for the V1a vasopressin receptors (V1aRs) in cultured cortical neurons [R.S. Yamazaki, Q. Chen, S.S. Schreiber, R.D. Brinton, V1a Vasopressin receptor mRNA expression in cultured neurons, astroglia, and oligodendroglia of rat cerebral cortex, Mol. Brain Res., 45 (1996) 138-140]. To determine whether these recognition sites are functional receptors, we have pursued the signal transduction mechanism associated with the V1a vasopressin receptor in enriched cultures of cortical neurons. Results of these studies demonstrate that exposure of cortical neurons to the selective V1 vasopressin receptor agonist, [Phe2,Orn8]-vasotocin, (V1 agonist) induced a significant accumulation of [3H]inositol-1-phosphate ([3H]IP1). V1 agonist-induced accumulation of [3H]IP1 was concentration dependent and exhibited a linear dose response curve. Time course analysis of V1 agonist-induced accumulation of [3H]IP1 revealed a significant increase by 20 min which then decreased gradually over the remaining 60 min observation period. V1 agonist-induced accumulation of [3H]IP1 was blocked by a selective V1a vasopressin receptor antagonist, (Phenylac1, D-Tyr(Me)2, Arg6,8, Lys-NH29)-vasopressin. Results of calcium fluorometry studies indicated that V1 agonist exposure induced a marked and sustained rise in intracellular calcium which was abolished in the absence of extracellular calcium. The loss of the rise in intracellular calcium was not due to a failure to induce PIP2 hydrolysis since activation of the phosphatidylinositol pathway occurred in the absence of extracellular calcium. V1 agonist activation of calcium influx was then investigated. V1 agonist-induced 45Ca2+ uptake was concentration dependent with a biphasic time course at 250 nM. Preincubation with the L-type calcium channel blocker, nifedipine, blocked V1 agonist-induced calcium influx suggesting V1 agonist-induced L-type calcium channel activation in cortical neurons. Furthermore, V1 agonist-induced calcium influx was blocked by both bisindolyleimide I (PKC inhibitor) and U-73122 (PLC inhibitor) suggesting a modulation of V1 agonist-induced L-type calcium channel activation by downstream components of the phosphatidylinositol signaling pathway such as protein kinase C. These results indicate that in cultured cortical neurons, V1a vasopressin receptor activation leads to induction of the phosphatidylinositol signaling pathway, influx of extracellular calcium via L-type calcium channel activation, and a rise in intracellular calcium which is dependent on V1a receptor activated influx of extracellular calcium. These data are the first to demonstrate an effector mechanism for the V1 vasopressin receptor in the cerebral cortex and provide a potential biochemical mechanism that may underlie vasopressin enhancement of memory function.
 ...
PMID:Vasopressin-induced calcium signaling in cultured cortical neurons. 963 Jun 55

An anthranyl moiety placed at the N terminus of a phosphotyrosine peptide potentiates the inhibitory effect of this small peptide on the binding of the Grb2 SH2 domain to the EGF receptor. Using molecular modeling procedures based on the Lck SH2 domain structure, this observation was rationalized in terms of a suitably favorable pi-pi stacking interaction between the anthranyl moiety and the arginine alphaA2 (ArgalphaA2) residue side-chain of Grb2 SH2. The crystal structure of the Grb2 SH2 domain in complex with the inhibitor 2-Abz-EpYINQ-NH2 (IC50 26 nM) has been solved in two different crystal forms at 2.1 and 1.8 A resolution. This structure confirms the modeling based on the Lck SH2 domain. The ArgalphaA2 residue is conserved in most SH2 domains. Thus, as expected, the anthranyl group also confers high affinity to small peptide ligands of other SH2 domains such as Lck-, PLC-gamma-amino-terminal and p85 amino-terminal SH2 domains as demonstrated by structure affinity relationships (SAR) data. These potent peptides with an amino-terminal surrogate group and the structure of Grb2 SH2 domain in complex with one such peptide represent good starting points for the design and optimization of new inhibitors of many SH2 domains.
J Mol Biol 1998 Jun 19
PMID:Structural basis for the high affinity of amino-aromatic SH2 phosphopeptide ligands. 964 78

The regulation of parathyroid hormone secretion by the chief cells of the parathyroid is mediated by a 7-transmembrane (7-TM) Ca2+-sensing receptor (CaR), which signals via activation of pertussis toxin-insensitive G proteins, causing stimulation of phosphatidylinositol-specific phospholipase C (PI-PLC). We have identified the PI-PLC isoforms expressed in two model systems utilized for studying CaR signal transduction, i.e. dispersed bovine parathyroid cells and a human embryonic kidney cell line (HEK 293) stably transfected with the human parathyroid CaR-cDNA. All of the eight PI-PLC isozymes examined in this study were found to be expressed to varying extents in the bovine parathyroid gland and in the CaR-transfected HEK cells as assessed by immunoblotting. We localized the expression of the more abundant isozymes (beta1, beta2, beta3, gamma1, gamma2, delta2) to the chief cells of the bovine parathyroid by immunocytochemistry, while the two less abundant isozymes (delta1, beta4) were not detectable in parathyroid sections. G proteins activated by 7-TM receptors are known to activate mainly PI-PLC of the beta class. Therefore, beta1, beta2, beta3 and beta4, all expressed in the bovine parathyroid, are candidate isozymes for coupling to the CaR. A comparison of the levels of expression of PI-PLC isozymes between CaR-transfected HEK cells and non-transfected HEK cells suggested that the expression of the CaR in this human cell line does not cause a significant up-regulation of any of the PLCbeta and PLCgamma isozymes. PLCdelta2, showing predominantly nuclear localization in the parathyroid, was the sole PI-PLC isozyme with higher levels of expression in CaR-transfected HEK cells.
J Mol Endocrinol 1998 Aug
PMID:Characterization of the phosphatidylinositol-specific phospholipase C isozymes present in the bovine parathyroid and in human kidney HEK293 cells stably transfected with the human parathyroid Ca2+-sensing receptor. 972 59


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