title: Defective cyclic adenosine 3'-5'-monophosphate-dependent phosphorylation of plasma membrane proteins in chemically and virally transformed cells.
abstract: Cyclic adenosine 3':5'-monophosphate (cyclic AMP)-dependent phosphorylation of endogenous plasma membrane proteins catalyzed by an endogenous plasma membrane protein kinase was assayed in purified plasma membrane preparations derived from nontransformed, methylcholanthrene-transformed, and simian virus 40 (SV40)-transformed BALB/3T3 cells. In nontransformed cells, cyclic AMP stimulated the phosphorylation of two proteins with molecular weights of 24,000 and 14,000. The labeling of these proteins could be inhibited by rabbit skeletal muscle protein kinase inhibitor. In methylcholanthrene-transformed cells, no cyclic AMP-dependent phosphorylation of endogenous plasma membrane proteins was observed. SV40-transformed cells also showed markedly decreased cyclic AMP-dependent phosphorylation of both endogenous plasma membrane substrates. Addition of exogenous cyclic AMP-dependent protein kinase from bovine kidney to plasma membrane preparations isolated from methylcholanthrene or SV40-transformed isolated from methylcholanthrene or SV40-transformed cells, however, catalyzed the cyclic AMP-dependent phosphorylation of both the M.W. 24,000 and M.W. 14,000 substrates. These data show that the plasma membranes of transformed cells have a defect in an endogenous cyclic AMP-dependent phosphorylation system and that this defect can be corrected by addition of an exogenous cyclic AMP-dependent protein kinase.
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D002472:Cell Transformation, Viral; D000242:Cyclic AMP / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008748:Methylcholanthrene; D051379:Mice; D008970:Molecular Weight; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D013539:Simian virus 40
chemical_list: D008565:Membrane Proteins; D010750:Phosphoproteins; D008748:Methylcholanthrene; D000242:Cyclic AMP; D011494:Protein Kinases