Nicotinic and muscarinic agonists, phorbol esters, and agents which raise cyclic AMP levels phosphorylate distinct groups of proteins in the superior cervical ganglion

Abstract

The phosphorylation of proteins in the superior cervical ganglion of the rat was investigated. Ganglia were incubated with 32Pi, and the 32P-labeled proteins in the ganglion were separated by two-dimensional electrophoresis and visualized by autoradiography. Approximately 40 distinct phosphoproteins could be visualized by these methods. The most heavily labeled ganglionic protein was an acidic protein with an Mr of approximately 83,000. Tyrosine hydroxylase was identified as a doublet of two closely-migrating radioactive spots. Treatment of intact ganglia with depolarizing agents, nicotinic and muscarinic agonists, phorbol esters, and agents that increase the content of cyclic adenosine 3':5'-monophosphate in the ganglion stimulated the incorporation of 32Pi into distinct but overlapping groups of phosphoproteins. All of these agents increased the phosphorylation of tyrosine hydroxylase. In contrast, only phorbol esters and muscarinic agonists increased the phosphorylation of the 83,000 ganglionic phosphoprotein. Our data are consistent with the idea that the various classes of agonists may activate distinct protein kinases in the ganglion.