Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A recently reported new member of the Vav family proteins, Vav3 has been identified as a Ros receptor protein tyrosine kinase (RPTK) interacting protein by yeast two-hybrid screening. Northern analysis shows that Vav3 has a broad tissue expression profile that is distinct from those of Vav and Vav2. Two species of Vav3 transcripts, 3.4 and 5.4 kb, were detected with a differential expression pattern in various tissues. Transient expression of Vav in 293T and NIH 3T3 cells demonstrated that ligand stimulation of several RPTKs (epidermal growth factor receptor [EGFR], Ros, insulin receptor [IR], and insulin-like growth factor I receptor [IGFR]) led to tyrosine phosphorylation of Vav3 and its association with the receptors as well as their downstream signaling molecules, including Shc, Grb2, phospholipase C (PLC-gamma), and phosphatidylinositol 3 kinase. In vitro binding assays using glutathione S-transferase-fusion polypeptides containing the GTPase-binding domains of Rok-alpha, Pak, or Ack revealed that overexpression of Vav3 in NIH 3T3 cells resulted in the activation of Rac-1 and Cdc42 whereas a deletion mutant lacking the N-terminal calponin homology and acidic region domains activated RhoA and Rac-1 but lost the ability to activate Cdc42. Vav3 induced marked membrane ruffles and microspikes in NIH 3T3 cells, while the N-terminal truncation mutants of Vav3 significantly enhanced membrane ruffle formation but had a reduced ability to induce microspikes. Activation of IR further enhanced the ability of Vav3 to induce membrane ruffles, but IGFR activation specifically promoted Vav3-mediated microspike formation. N-terminal truncation of Vav3 activated its transforming potential, as measured by focus-formation assays. We conclude that Vav3 mediates RPTK signaling and regulates GTPase activity, its native and mutant forms are able to modulate cell morphology, and it has the potential to induce cell transformation.
 ...
PMID:Vav3 mediates receptor protein tyrosine kinase signaling, regulates GTPase activity, modulates cell morphology, and induces cell transformation. 1109 73

Crosslinking of multivalent antigen bound IgE transduces FcepsilonRI mediated signaling cascades, which activate nonreceptor-type protein-tyrosine kinases and subsequent tyrosine phosphorylation of cellular proteins, and these are critical elements for degranulation in mast cells. We cloned a novel adaptor molecule, signal transducing adaptor protein (STAP)-2 containing PH and SH2-like domains as a c-fms interacting protein. STAP-2 was identical to a recently cloned adaptor molecule, BKS, a substrate of BRK (breast tumor kinase) tyrosine kinase, although its function is still unknown. To examine a novel function of STAP-2/BSK, we expressed STAP-2/BSK or its mutants in rat basophilic leukemia RBL-2H3 cells. Overexpression of STAP-2/BSK resulted in a suppression of FcepsilonRI-mediated calcium mobilization and degranulation. FcepsilonRI-induced tyrosine phosphorylation of phospholipase C-gamma (PLC-gamma) but not Syk was significantly suppressed in these cells. Furthermore, STAP-2/BSK associated with PLC-gamma in vivo. These data indicate that STAP-2/BSK negatively controls the FcepsilonRI-mediated calcium mobilization and degranulation by direct modulation of tyrosine phosphorylation of PLC-gamma.
 ...
PMID:Regulation of FcepsilonRI-mediated signaling by an adaptor protein STAP-2/BSK in rat basophilic leukemia RBL-2H3 cells. 1281 85

A GTPase activating protein (GAP), p122, has previously been cloned as a phospholipase C (PLC)delta1-interacting protein. p122 shows a specific GAP activity for Rho and enhances the enzyme activity of PLCdelta1. In this study, we examined the localization and functions of p122/RhoGAP, using enhanced green fluorescent protein (EGFP)-tagged proteins. EGFP-p122 was observed as punctate structures at the plasma membrane of BHK (fibroblastic) cells and MDCK (epithelial) cells. This patchy distribution depended on membrane cholesterol levels and the C-terminal region of p122 containing the GAP domain was responsible for it. Sucrose density gradient centrifugation and immunostaining of caveolin-1 revealed that p122 was localized in caveolin-enriched membrane domains mainly via its GAP domain. We demonstrated that transient expression of EGFP-p122 caused internalization of caveolin-1. Moreover, when the EGFP-tagged GAP domain was introduced in another fibroblastic cell line, NRK cells, punctate fluorescent structures were co-localized with caveolin-1. In this case, caveolin-1-positive structures were found in patches of F-actin, unlike those of untransfected cells that formed linear arrays along with actin stress fibres. These results suggest that p122 is localized in caveolae and plays an important role in caveolin distribution through reorganization of the actin cytoskeleton.
 ...
PMID:A PLCdelta1-binding protein, p122/RhoGAP, is localized in caveolin-enriched membrane domains and regulates caveolin internalization. 1472 5

Engagement of the B-cell antigen receptor (BCR) activates kinases of the Src and Syk families and signaling complexes assembled by adaptor proteins, which dictate B-cell fate and function. The adaptor 3BP2/SH3BP2, an Abl Src homology domain 3 (SH3)-binding and Syk-kinases interacting protein, exhibits positive regulatory roles in T, natural killer (NK), and basophilic cells. However, its involvement in BCR signaling is completely unknown. Here we show that 3BP2 is tyrosine phosphorylated following BCR aggregation on B lymphoma cells, and that 3BP2 is a substrate for Syk and Fyn, but not Btk. To further explore the function of 3BP2 in B cells, we screened a yeast 2-hybrid B-lymphocyte library and found 3BP2 as a binding partner of Vav proteins. The interaction between 3BP2 and Vav proteins involved both constitutive and inducible mechanisms. 3BP2 also interacted with other components of the BCR signaling pathway, including Syk and phospholipase C gamma (PLC-gamma). Furthermore, overexpression and RNAi blocking experiments showed that 3BP2 regulated BCR-mediated activation of nuclear factor of activated T cells (NFATs). Finally, evidence was provided that 3BP2 functionally cooperates with Vav proteins and Rho GTPases to activate NFATs. Our results show that 3BP2 may regulate BCR-mediated gene activation through Vav proteins.
 ...
PMID:The adaptor protein 3BP2 associates with VAV guanine nucleotide exchange factors to regulate NFAT activation by the B-cell antigen receptor. 1534 94

Effector functions mediated by NK cells involve cytotoxicity and transcription-dependent production and release of cytokines and chemokines. Although the JAK/STAT pathway mediates lymphokine-induced transcriptional regulation in NK cells, very little is known about transcriptional regulation induced during cell-cell contact. We demonstrate that the Wiskott-Aldrich syndrome protein (WASp) is an important component for integration of signals leading to nuclear translocation of NFAT2 and NF-kappaB (RelA) during cell-cell contact and NKp46-dependent signaling. This WASp function is independent of its known role in F-actin polymerization and cytoskeletal rearrangement. Absence of WASp results in decreased accumulation of calcineurin, WASp-interacting protein, and molecules upstream of calcium mobilization, i.e., activated ZAP70 and phospholipase C-gamma1, in the disorganized NK cell immune synapse. Production of GM-CSF, but not IFN-gamma, is decreased, while natural cytotoxicity of Wiskott-Aldrich syndrome-NK cells is maintained. Our results indicate that WASp independently regulates its dual functions, i.e., actin cytoskeletal remodeling and transcription in NK cells.
 ...
PMID:The Wiskott-Aldrich syndrome protein regulates nuclear translocation of NFAT2 and NF-kappa B (RelA) independently of its role in filamentous actin polymerization and actin cytoskeletal rearrangement. 1572 66

Receptor for Activated C Kinase 1 (RACK1), a novel G betagamma-interacting protein, selectively inhibits the activation of a subclass of G betagamma effectors such as phospholipase C beta2 (PLCbeta2) and adenylyl cyclase II by direct binding to G betagamma (Chen, S., Dell, E. J., Lin, F., Sai, J., and Hamm, H. E. (2004) J. Biol. Chem. 279, 17861-17868). Here we have mapped the RACK1 binding sites on G betagamma. We found that RACK1 interacts with several different G betagamma isoforms, including G beta1gamma1, Gbeta1gamma2, and Gbeta5gamma2, with similar affinities, suggesting that the conserved residues between G beta1 and G beta5 may be involved in their binding to RACK1. We have confirmed this hypothesis and shown that several synthetic peptides corresponding to the conserved residues can inhibit the RACK1/G betagamma interaction as monitored by fluorescence spectroscopy. Interestingly, these peptides are located at one side of G beta1 and have little overlap with the G alpha subunit binding interface. Additional experiments indicate that the G betagamma contact residues for RACK1, in particular the positively charged amino acids within residues 44-54 of G beta1, are also involved in the interaction with PLCbeta2 and play a critical role in G betagamma-mediated PLCbeta2 activation. These data thus demonstrate that RACK1 can regulate the activity of a G betagamma effector by competing for its binding to the signal transfer region of G betagamma.
 ...
PMID:RACK1 binds to a signal transfer region of G betagamma and inhibits phospholipase C beta2 activation. 1605 95

Phospholipase C-beta (PLC-beta) isozymes (EC 3.1.4.11) hydrolyze the membrane phospholipid phosphatidylinositol-4,5-bisphosphate to generate intracellular second messenger signaling molecules inositol-1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) in response to receptor activation and other cellular stimuli. PLCbeta1 and PLCbeta3 isozymes were previously demonstrated to bind the calcium-sensitive molecule calmodulin [McCullar JS, Larsen SA, Millimaki RA, Filtz TM. Calmodulin is a phospholipase C-{beta} interacting protein. J Biol Chem 2003;278(36):33708-13]. We have now shown through fluorescence anisotropy that calmodulin/PLCbeta3 affinities increase with increasing calcium in a physiologically relevant concentration range. The bimolecular affinity constants for calmodulin interaction with PLCbeta1 or PLCbeta3 were estimated as 260 and 200 nM, respectively, from fluorescence anisotropy data. There was no effect of calmodulin on basal or G alpha q-stimulated catalytic activity for either isozyme. However, the interaction between calmodulin and PLCbeta3 leads to potentiation of activation by the G-protein beta gamma dimer in an in vitro assay. 1321N1 cells treated with calmodulin inhibitors concurrent with and post-stimulation of muscarinic receptors significantly reduced [3H]PIP hydrolysis. Together these data are suggestive of cooperative role for calmodulin in the G-protein beta gamma dimer-stimulated activity of PLCbeta3.
 ...
PMID:Calmodulin potentiates G beta gamma activation of phospholipase C-beta3. 1711 46

As in the case of most G protein-coupled receptors, agonist stimulation of human oxytocin receptors (OTRs) leads to desensitization and internalization; however, little is known about the subsequent intracellular OTR trafficking, which is crucial for reestablishing agonist responsiveness. We examined receptor resensitization by first using HEK293T cells stably expressing human OTRs. Upon agonist activation, the receptors were almost completely sequestered inside intracellular compartments that were not labeled by lysosomal markers, thus indicating that the internalized receptors were not sorted to these degrading organelles. Binding and fluorescence assays showed that almost 85% of the receptors had returned to the cell surface after 4 h, by which time cell responsiveness to the agonist was also completely restored, as shown by measuring phospholipase C activation. Similar results were also obtained in the presence of cycloheximide, thus indicating that receptor recycling and not de novo receptor synthesis was responsible for the resensitization. Notably, very similar internalization and recycling kinetics were observed in endogenous OTRs expressed on myometrial cells. We also investigated the role of beta-arrestin2 in OTR recycling as these receptors have been previously classified as slowly or nonrecycling receptors on the basis of their stable association with this interacting protein. Our data suggest that the stable OTR/beta-arrestin2 interaction plays an important role in determining the rate of recycling of human OTRs, but does not determine the fate of endocytosed receptors. Subsequent investigations of receptor recycling pathways showed that OTRs localize in vesicles containing the Rab5 and Rab4 small GTPases (markers of the "short cycle"), whereas there was no colocalization with Rab11 (a marker of the "long cycle") or Rab7 (a marker of vesicles directed to endosomal/lysosomal compartments). Taken together, these data indicate that OTRs are capable of very efficient and complete resensitization due to receptor recycling via the short cycle.
 ...
PMID:Intracellular trafficking of the human oxytocin receptor: evidence of receptor recycling via a Rab4/Rab5 "short cycle". 1912 85

Gbeta subunits from heterotrimeric G-proteins (guanine nucleotide-binding proteins) directly bind diverse proteins, including effectors and regulators, to modulate a wide array of signaling cascades. These numerous interactions constrained the evolution of the molecular surface of Gbeta. Although mammals contain five Gbeta genes comprising two classes (Gbeta1-like and Gbeta5-like), plants and fungi have a single ortholog, and organisms such as Caenorhabditis elegans and Drosophila melanogaster contain one copy from each class. A limited number of crystal structures of complexes containing Gbeta subunits and complementary biochemical data highlight specific sites within Gbetas needed for protein interactions. It is difficult to determine from these interaction sites what, if any, additional regions of the Gbeta molecular surface comprise interaction interfaces essential to Gbeta's role as a nexus in numerous signaling cascades. We used a comparative evolutionary approach to identify five known and eight previously unknown putative interfaces on the surface of Gbeta. We show that one such novel interface occurs between Gbeta and phospholipase C beta2 (PLC-beta2), a mammalian Gbeta interacting protein. Substitutions of residues within this Gbeta-PLC-beta2 interface reduce the activation of PLC-beta2 by Gbeta1, confirming that our de novo comparative evolutionary approach predicts previously unknown Gbeta-protein interfaces. Similarly, we hypothesize that the seven remaining untested novel regions contribute to putative interfaces for other Gbeta interacting proteins. Finally, this comparative evolutionary approach is suitable for application to any protein involved in a significant number of protein-protein interactions.
 ...
PMID:Prediction of protein-protein interfaces on G-protein beta subunits reveals a novel phospholipase C beta2 binding domain. 1964 92

The role of the Wiskott-Aldrich syndrome protein (WASp) in platelet function is unclear because platelets that lack WASp function normally. WASp constitutively associates with WASp-interacting protein (WIP) in resting and activated platelets. The role of WIP in platelet function was investigated using mice that lack WIP or WASp. WIP knockout (KO) platelets lack WASp and thus are double deficient. WIP KO mice have a thrombocytopenia, similar to WASp KO mice, resulting in part from enhanced platelet clearance. Most WIP KO, but not WASp KO, mice evolved platelet-associated immunoglobulins (Ig) of the IgA class, which normalize their platelet survival but diminish their glycoprotein VI (GPVI) responses. Protein tyrosine phosphorylation, including that of phospholipase C-gamma2, and calcium mobilization are impaired in IgA-presenting WIP KO platelets stimulated through GPVI, resulting in defects in alpha-granule secretion, integrin alphaIIbbeta3 activation, and actin assembly. The anti-GPVI antibody JAQ1 induces the irreversible loss of GPVI from circulating platelets in wild-type mice, but not in WIP KO mice that bear high levels of platelet-associated IgAs. Together, the data indicate that platelet-associated IgAs negatively modulate GPVI signaling and function in WIP KO mice.
 ...
PMID:Platelet-associated IgAs and impaired GPVI responses in platelets lacking WIP. 1996 14


1 2 Next >>