THE ALPHA-SUBUNIT MESSENGER-RNAS FOR G(S) AND G(O2) ARE DIFFERENTIALLY REGULATED BY PROTEIN-KINASE-A AND PROTEIN-KINASE-C IN RAT SERTOLI CELLS

In the present study, we have examined regulatory effects of protein k inase A and protein kinase C activation by 8-CPTcAMP and TPA, respecti vely, on mRNAs for various G protein alpha-subunits and corresponding immunoreactive proteins in rat Sertoli cells. G(s) alpha and G(o) alph a mRNA levels were transiently increased 1.5-fold and 4-fold, respecti vely, by 8-CPTcAMP in cultured Sertoli cells. This up-regulation of mR NAs for G(s) alpha and G(o) alpha was also observed when Sertoli cells were incubated in the presence of FSH. When protein synthesis was inh ibited by cycloheximide, the cAMP-mediated stimulation of G(s) alpha m RNA was abolished, whereas G(o) alpha mRNA was superinduced to a 50- t o 100-fold higher level than basal. Activation of protein kinase C wit h TPA had a strong, synergistic effect on cAMP-mediated stimulation of G(s) alpha mRNA, whereas the cAMP-mediated stimulation of G(o) alpha mRNA was completely blocked. Surprisingly, changes in mRNA levels were not accompanied by any alterations in the levels of immunoreactive G( s) alpha and G(o) alpha proteins.