Role of specific @entity7131 isozymes in mediating epidermal growth factor, thyrotropin-releasing hormone, and @entity4621 regulation of the @entity35 XXXX promoter in GH4/ @entity35 pituitary cells.

@entity2366 @entity9295 @entity5 @entity141 @entity12703 @entity7131 @entity4621 @entity1218 @entity3695 @entity866 @entity30825 @entity35 @entity11616
Epidermal growth factor (EGF) and @entity1218 both produce enhanced @entity3695 ( @entity3695 ) gene transcription and @entity3695 secretion in GH4 @entity35 pituitary @entity5 cell lines. These agents also activate @entity7131 ( @entity7131 ) in these cells. Previous studies have implicated the PKCepsilon isozyme in mediating @entity1218 -induced @entity3695 secretion. However, indirect studies using @entity4621 down-regulation to investigate the role of @entity7131 in EGF- and @entity1218 -induced @entity3695 gene transcription have been inconclusive. In the present study, we examined the role of multiple @entity7131 isozymes on EGF- and @entity1218 -induced activation of the @entity3695 promoter by utilizing general and selective @entity7131 inhibitors and by expression of genes for wild-type and kinase-negative forms of the @entity7131 isozymes. Multiple nonselective @entity7131 inhibitors, including @entity866 , @entity30825 I, and @entity11616 , inhibited both EGF and @entity1218 induced @entity35 @entity3695 promoter activity. @entity1218 effects were more sensitive to @entity11616 , a competitive inhibitor of @entity2366 , whereas @entity9295 , a selective inhibitor of @entity141 -dependent PKCs, produced a modest inhibition of EGF but no inhibition of @entity1218 effects. @entity12703 , a specific inhibitor of the novel nPKCdelta isozyme, significantly blocked both EGF and @entity1218 effects. Overexpression of genes encoding PKCs alpha, betaI, betaII, delta, gamma, and lambda failed to enhance either EGF or @entity1218 responses, whereas overexpression of nPKCeta enhanced the EGF response. Neither stable nor transient overexpression of nPKCepsilon produced enhancement of EGF- or @entity1218 -induced @entity3695 promoter activity, suggesting that different processes regulate @entity3695 transcription and hormone secretion. Expression of a kinase inactive nPKCdelta construct produced modest inhibition of EGF-mediated rPRL promoter activity. Taken together, these data provide evidence for a role of multiple @entity7131 isozymes in mediating both EGF and @entity1218 stimulated @entity3695 gene transcription. Both EGF and @entity1218 responses appear to require the novel isozyme, nPKCdelta, whereas nPKCeta may also be able to transmit the EGF response. Inhibitor data suggest that the EGF response may also involve @entity141 -dependent isozymes, whereas the @entity1218 response appears to be more dependent on @entity2366 .
