title: Cyclic AMP-dependent phosphorylation of filamin in mammalian smooth muscle.
abstract: Filamin is a high molecular weight actin-binding protein found in large quantities in smooth muscle and other non-muscle cells. We have studied the phosphorylation of filamin in a mammalian smooth muscle, the guinea pig vas deferens. Intact vas deferens incorporated [32P]orthophosphate into filamin. Incubation of particulate fractions of vas deferens with [gamma-32P]ATP resulted in 32P-labeling of filamin. Cyclic AMP stimulated this phosphorylation, whereas cyclic GMP and Ca2+ had no effect. Purified vas deferens filamin can be phosphorylated by purified cyclic AMP-dependent protein kinase. We have compared cyclic AMP and cyclic GMP effects on phosphorylation in smooth muscle. Cyclic GMP stimulated phosphorylation of two particulate proteins, G-I (Mr = 130,000) a protein previously described by Casnellie, J. E., and Greengard, P. (1974) Proc. Natl. Acad, Sci. U.S.A. 71, 1891-1895 and G-III (Mr = 240,000). Both proteins and the kinase responsible for their phosphorylation appear to be membrane-bound. Phosphorylation of both proteins is stimulated by cyclic GMP (Ka = 3 x 10(-8) M), cyclic AMP (Ka = 3 x 10(-7) M), and to a lesser degree by Ca2+. In contrast, filamin phosphorylation is due to a soluble kinase stimulated only by cyclic AMP (Ka = 3 x 10(-7) M) and not by cyclic GMP or Ca2+.
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D003285:Contractile Proteins / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism; D006168:Guinea Pigs; D008297:Male; D009130:Muscle, Smooth / Q000378:metabolism*; D010750:Phosphoproteins / Q000096:biosynthesis*; D011494:Protein Kinases / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014649:Vas Deferens / Q000378:metabolism
chemical_list: D000199:Actins; D002352:Carrier Proteins; D003285:Contractile Proteins; D010750:Phosphoproteins; D000242:Cyclic AMP; D011494:Protein Kinases; D006152:Cyclic GMP; D002118:Calcium