"PTH stimulates PLC beta and gamma isozymes in rat enterocytes: influence of ageing.

GENTILI C; BOLAND, RICARDO; RUSSO DE BOLAND ANA

Cellular Signalling

Elsevier Science Inc.

Lugar: Glasgow Inglaterra; Año: 2001 vol. 13 p. 131 - 138

0898-6568

We previously reported that in rat duodenal cells (enterocytes), parathyroid hormone (PTH [1-34] PTH) stimulates the hydrolysis of polyphosphoinositides by phospholipase C (PLC), generating the second messengers inositol trisphosphate (IP3) and diacylglycerol (DAG) and that this mechanism is severely altered in old animals. In the present study, we show that PTH [1-34]-dependent IP3 release in young rats was blocked to a great extent by an antibody against guanine nucleotide binding protein Galfaq/11, indicating that the hormone activates a beta isoform of PLC coupled to the alfa subunit of Gq/11. In addition, PTH rapidly (within 30 s, with maximal effects at 1 min) stimulated tyrosine phosphorylation of PLCgamma in a dose-dependent fashion (10 -8 -10 -7M). The hormone response was specific as PTH [7-34] was without effects. The tyrosine kinase inhibitors, genistein (100 mM) and herbimycin (2 mM), suppressed PTH-dependent PLCgamma tyrosine phosphorylation. Stimulation of PLCgamma tyrosine phosphorylation by PTH [1-34] greatly decreased with ageing. PP1 (10 mM), a specific inhibitor of the Src family of tyrosine kinases, completely abolished PLCgamma phosphorylation. The hormone-induced Src tyrosine dephosphorylation, a major mechanism of Src activation, an effect that was blunted in old animals. These results indicate that in rat enterocytes PTH generates IP3 mainly through G-protein-coupled PLCbeta and stimulates PLCgamma phosphorylation via the nonreceptor tyrosine kinase Src. Impairment of PTH activation of both PLC isoforms upon ageing may result in abnormal hormone regulation of cell Ca and proliferation in the duodenum.