| 18322273 |
Zhong M, Murtazina DA, Phillips J, Ku CY, Sanborn BM: Multiple signals regulate phospholipase CBeta3 in human myometrial cells. Biol Reprod. 2008 Jun;78(6):1007-17. Epub 2008 Mar 5.
Phospholipase CB3 (PLCB3) serine (1105) (S (1105)), a substrate for multiple protein kinases, represents a potential point of convergence of several signaling pathways in the myometrium. To explore this hypothesis, the regulation of PLCB3-S (1105) phosphorylation (P-S (1105)) was studied in immortalized and primary human myometrial cells. 8-[4-chlorophenylthio] (CPT)-cAMP and calcitonin gene-related peptide (CALCA) transiently increased P-S (1105). Relaxin also stimulated P-S (1105); this effect was partially blocked by the protein kinase A (PRKA) inhibitor, Rp-8-CPT-cAMPS. Oxytocin, which stimulates Galphaq-mediated pathways, also rapidly increased P-S (1105), as did prostaglandin F2alpha and ATP. Oxytocin-stimulated phosphorylation was blocked by protein kinase C (PRKC) inhibitor Go6976 and by pretreatment overnight with a phorbol ester. Cypermethrin, a PP2B phosphatase inhibitor, but not okadaic acid, a PP1/PP2A inhibitor, prolonged the effect of CALCA on P-S (1105), whereas the reverse was the case for the oxytocin-stimulated increase in P-S (1105). PLCB3 was the predominant PLC isoform expressed in the myometrial cells and PLCB3 short hairpin RNA constructs significantly attenuated oxytocin-stimulated increases in intracellular calcium. oxytocin-induced phosphatidylinositol (PI) turnover was inhibited by CPT-cAMP and okadaic acid, but was enhanced by pretreatment with Go6976. CPT-cAMP inhibited oxytocin-stimulated PI turnover in the presence of overexpressed PLCB3, but not overexpressed PLCB3-S (1105) A. These data demonstrate that both negative crosstalk from the cAMP/PRKA pathway and a negative feedback loop in the oxytocin/G protein/PLCB pathway involving PRKC operate in myometrial cells and suggest that different protein phosphatases predominate in mediating P-S (1105) dephosphorylation in these pathways. The integration of multiple signal components at the level of PLCB3 may be important to its function in the myometrium. |
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