Negative regulation of parathyroid hormone (PTH)-activated phospholipase C by PTH/PTH-related peptide receptor phosphorylation and protein kinase A.

PTH binding to the PTH/PTHrP receptor activates adenylate cyclase/protein kinase A and phospholipase C (PLC) pathways and increases receptor phosphorylation. The mechanisms regulating PTH activation of PLC signaling are poorly understood. In the current study, we explored the role of PTH/PTHrP receptor phosphorylation and in PTH activation of PLC. When treated with PTH, LLCPK-1 cells stably expressing a green fluorescent protein (GFP)-tagged wild-type (WT) PTH/PTHrP receptor show a small dose-dependent increase in PLC signaling as measured by inositol trisphosphate accumulation assay. In contrast, PTH treatment of LLCPK-1 cells stably expressing a GFP-tagged receptor mutated in its carboxyl-terminal tail so that it cannot be phosphorylated (PD-GFP) results in significantly higher PLC activation (P<0.001). The effects of PTH on PLC activation are dose dependent and reach maximum at the 100 nm PTH dose. When WT receptor-expressing cells are pretreated with H89, a specific inhibitor of PTH activation of PLC signaling is enhanced in a dose-dependent manner. H89 pretreatment in PD-GFP cells causes a further increase in PLC activation in response to PTH treatment. Interestingly, PTH and forskolin (adenylate pathway activator) treatment causes an increase in PLCbeta3 phosphorylation at the Ser1105 inhibitory site and that increase is blocked by the duanyu1529 inhibitor, H89. Expression of a mutant PLCbeta3 in which Ser1105 was mutated to alanine (PLCbeta3-SA), in WT or PD cells increases PTH stimulation of inositol 1,4,5-trisphosphate formation. Altogether, these data suggest that PTH signaling to PLC is negatively regulated by PTH/PTHrP receptor phosphorylation and Furthermore, phosphorylation at Ser1105 is demonstrated as a regulatory mechanism of PLCbeta3 by

KEYWORDS: {{ getKeywords(articleDetailText.words) }}