DIFFERENTIAL CALCIUM-DEPENDENCE IN THE ACTIVATION OF C-JUN KINASE ANDMITOGEN-ACTIVATED PROTEIN-KINASE BY MUSCARINIC ACETYLCHOLINE-RECEPTORS IN RAT 1A CELLS

Carbachol stimulation of the muscarinic acetylcholine m1 receptor (m1R ), stably expressed in Rat 1a fibroblasts, resulted in a calcium-depen dent activation of c-Jun kinase (JNK). Stimulation of the muscarinic a cetylcholine m2 receptor (m2R), stably expressed in Rat la fibroblasts , resulted in a G(i)-mediated activation of JNK that was weak relative to that observed with the m1R. Chelation of calcium inhibited the m2R -mediated activation of JNK but not the robust m2R stimulation of mito gen-activated protein kinase (MARK) activity. These findings demonstra te a role for the second messenger, calcium, in the differential regul ation of the activity of JNK and MARK in Rat 1a cells.