Cyclic nucleotide-dependent phosphorylation of proteins in rabbit ciliary processes.

Cyclic nucleotide-dependent protein phosphorylation in albino rabbit ciliary processes was studied in particulate and soluble fractions of the tissue by the technique of SDS-polyacrylamide gel electrophoresis and autoradiography. In the presence of gamma-32P-ATP, the soluble fraction showed increased phosphorylation of proteins of 200, 32 and 16 kDa molecular weight when 10 microM cAMP was added. Protein phosphorylation increased with time up to 5 min. No significant augmentation of phosphorylation was observed in the presence of 10 microM cGMP compared to control. In the particulate fraction, proteins with molecular weights of 200, 160, 105, 72, 58, 32 and 16 kDa showed increased phosphorylation in the presence of 10 microM cAMP. Phosphorylation caused by the addition of cAMP was maximal between 30 sec and 1 min for the particulate membrane fraction, but with longer incubation times the incorporation of phosphate residues decreased. The same molecular weight proteins of the membrane fraction that were phosphorylated in a cAMP-dependent manner were phosphorylated in the absence of exogenous cAMP by addition of either the catalytic subunit of cAMP-dependent protein kinase or activators of membrane-bound adenylate cyclase such as l-isoproterenol, vasoactive intestinal peptide, aluminum fluoride or forskolin. A cAMP-dependent dephosphorylation of a 56 kDa protein was observed in the membrane fraction. Cyclic GMP did not cause observable changes in the pattern of protein phosphorylation in the particulate fraction of rabbit ciliary processes.(ABSTRACT TRUNCATED AT 250 WORDS)