Inhibition of phosphorylation of troponin I in rat heart by adenosine and 5'-chloro-5'-deoxyadenosine.
We have investigated the effects of adenosine on protein phosphorylation in extracts of rat heart. Incubation of a myofibrillar fraction with [gamma-32P]ATP resulted in the phosphorylation of several proteins by endogenous protein kinases. The adenosine analog 5'-chloro-5'-deoxyadenosine inhibited the phosphorylation of a 29 kD protein in this preparation. The protein was identified as cardiac troponin I (cTnI) by two-dimensional gel electrophoresis, using purified cTnI as standard. Addition of the catalytic subunit of cAMP-dependent protein kinase to the myofibrillar fraction increased phosphorylation of cTnI; this increase was inhibited by 5'-chloro-5'-deoxyadenosine and adenosine. Phosphorylation of purified cTnI by the catalytic subunit was also inhibited by 5'-chloro-5'-deoxyadenosine. Under these conditions used, 50% inhibition of phosphorylation by either endogenous or exogenous kinase was observed at approximately 50 microM 5'-chloro-5'-deoxyadenosine or adenosine. The inhibition described here occurred independently of catecholamines. The effects of ADP, AMP, and adenine on cTnI phosphorylation are also described.
Rosenthal
R A
RA
Graduate Department of Biochemistry, Brandeis University, Waltham, MA 02254.
Lowenstein
J M
JM
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D017338:Cladribine; D003839:Deoxyadenosines / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects*; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D014336:Troponin / Q000302:isolation & purification / Q000378:metabolism*; D019210:Troponin I
D003839:Deoxyadenosines; D014336:Troponin; D019210:Troponin I; D017338:Cladribine; C044739:5'-chloro-5'-deoxyadenosine; D011494:Protein Kinases; D000241:Adenosine