STIMULATION OF MUSCARINIC RECEPTORS INDUCES EXPRESSION OF INDIVIDUAL FOS AND JUN GENES THROUGH DIFFERENT TRANSDUCTION PATHWAYS

The transduction pathways coupling muscarinic receptors to induction o f fos and jun genes were investigated in neuroblastoma SH-SY5Y cells. Stimulation with carbachol induced expression of c-fos, fosB, c-jun, j unB, and junD. This effect was abolished by pretreatment with atropine , indicating an involvement of muscarinic receptors. These genes were also induced by activation of protein kinase C with phorbol ester or b y elevating the intracellular Ca2+ concentration with a Ca2+ ionophore . The Ca2+ effect was inhibited by KN-62, suggesting an induction thro ugh Ca2+/calmodulin-dependent kinase II. Inhibition of protein kinase C with GF109203X suppressed the carbachol-stimulated increase in mRNA levels of c-fos, fosB, and junB by similar to 70% but had only minor e ffects on the expression of c-jun and junD. On the other hand, preincu bation with KN-62 attenuated the carbachol-induced increase in c-jun a nd junD expression by 70% but had no effect on c-fos, fosB, and junB m RNA levels, Simultaneous inhibition of both protein kinase C and Ca2+/ calmodulin-dependent kinase II completely abolished the carbachol-stim ulated expression of c-jun and junD, but c-fos, fosB, and junB were st ill expressed to a certain extent under this condition. Comparison of the inhibitory effects of GF109203X and Go 6976 suggests the involveme nt of classical protein kinase C isozymes in muscarinic receptor-stimu lated expression of fos and jun genes. These results demonstrate that the muscarinic receptor-induced expression of individual fos and jun g enes is regulated via different pathways, primarily protein kinase C o r Ca2+/calmodulin-dependent kinase II.