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

Increasing evidence links the activation of Rho family GTPases to the stimulation of lipid hydrolysis catalyzed by phospholipase C (PLC)-beta isozymes. To better define this relationship, members of a library of recombinant Rho GTPases were screened for their capacity to directly engage various purified PLC-beta isozymes. Of the 17 tested members of the Rho family, only the active isoforms of Rac (Rac1, Rac2, and Rac3) both stimulate PLC-beta activity in vivo and bind PLC-beta2 and PLC-beta3, but not PLC-beta1, in vitro. Furthermore, the recognition site for Rac GTPases was localized to the pleckstrin homology (PH) domain of PLC-beta2, and this PH domain is fully sufficient to selectively interact with the active versions of the Rac GTPases, but not with other similar Rho GTPases. Together, these findings present a quantitative evaluation of the direct interactions between Rac GTPases and PLC-beta isozymes and define a novel role for the PH domain of PLC-beta2 as a putative effector site for Rac GTPases.
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PMID:The pleckstrin homology domain of phospholipase C-beta2 as an effector site for Rac. 1265 29

Unique among the phospholipase C isozymes, the recently identified phospholipase C-epsilon (PLC-epsilon) contains an amino-terminal CDC25 domain capable of catalyzing nucleotide exchange on Ras family GTPases as well as a tandem array of Ras-associating (RA) domains near its carboxyl terminus that are effector binding sites for activated H-Ras and Rap. To determine whether other small GTPases activate PLC-epsilon, we measured inositol phosphate accumulation in COS-7 cells expressing a broad range of GTPase-deficient mutants of Ras superfamily proteins. RhoA, RhoB, and RhoC all markedly stimulated inositol phosphate accumulation in PLC-epsilon-expressing cells. This stimulation matched or exceeded phospholipase activation promoted by co-expression of PLC-epsilon with the known regulators Ras, Galpha12/13, or Gbeta1gamma2. In contrast, little effect was observed with the other Rho family members Rac1, Rac2, Rac3, and Cdc42. Truncation of the two carboxyl-terminal RA domains caused loss of responsiveness to H-Ras but not to Rho. Truncation of PLC-epsilon to remove the CDC25 and pleckstrin homology (PH) domains also did not cause loss of responsiveness to Rho, Galpha12/13, or Gbeta1gamma2. Comparative sequence analysis of mammalian phospholipase C isozymes revealed a unique approximately 65 amino acid insert within the catalytic core of PLC-epsilon not present in PLC-beta, gamma, delta, or zeta. A PLC-epsilon construct lacking this region was no longer activated by Rho or Galpha12/13 but retained regulation by Gbetagamma and H-Ras. GTP-dependent interaction of Rho with PLC-epsilon was illustrated in pull-down experiments with GST-Rho, and this interaction was retained in the PLC-epsilon construct lacking the unique insert within the catalytic core. These results are consistent with the conclusion that Rho family GTPases directly interact with PLC-epsilon by a mechanism independent of the CDC25 or RA domains. A unique insert within the catalytic core of PLC-epsilon imparts responsiveness to Rho, which may signal downstream of Galpha12/13 in the regulation of PLC-epsilon, because activation by both Rho and Galpha12/13 is lost in the absence of this sequence.
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PMID:Direct activation of phospholipase C-epsilon by Rho. 1290 Apr 2

The regulation of the two isoforms of phospholipase C-gamma, PLCgamma(1) and PLCgamma(2), by cell surface receptors involves protein tyrosine phosphorylation as well as interaction with adapter proteins and phosphatidylinositol 3,4,5-trisphosphate (PtdInsP(3)) generated by inositol phospholipid 3-kinases (PI3Ks). All three processes may lead to recruitment of the PLCgamma isozymes to the plasma membrane and/or stimulation of their catalytic activity. Recent evidence suggests that PLCgamma may also be regulated by Rho GTPases. In this study, PLCgamma(1) and PLCgamma(2) were reconstituted in intact cells and in a cell-free system with Rho GTPases to examine their influence on PLCgamma activity. PLCgamma(2), but not PLCgamma(1), was markedly activated in intact cells by constitutively active Rac1(G12V), Rac2(G12V), and Rac3(G12V) but not by Cdc42(G12V) and RhoA(G14V). The mechanism of PLCgamma(2) activation was apparently independent of phosphorylation of tyrosine residues known to be modified by PLCgamma(2)-activating protein-tyrosine kinases. Activation of PLCgamma(2) by Rac2(G12V) in intact cells coincided with a translocation of PLCgamma(2) from the soluble to the particulate fraction. PLCgamma isozyme-specific activation of PLCgamma(2) by Rac GTPases (Rac1 approximately Rac2 > Rac3), but not by Cdc42 or RhoA, was also observed in a cell-free system. Herein, activation of wild-type Rac GTPases with guanosine 5'-(3-O-thio)triphosphate caused a marked stimulation of PLCgamma(2) but had no effect on the activity of PLCgamma(1). PLCgamma(1) and PLCgamma(2) have previously been shown to be indiscriminately activated by PtdInsP(3) in vitro. Thus, the results suggest a novel mechanism of PLCgamma(2) activation by Rac GTPases involving neither protein tyrosine phosphorylation nor PI3K-mediated generation of PtdInsP(3).
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PMID:Isozyme-specific stimulation of phospholipase C-gamma2 by Rac GTPases. 1617 25