title: Regulation of endogenously catalyzed ADP-ribosylation in adipocyte plasma membranes by Ca2+ and calmodulin.
abstract: The effects of Ca2+ and calmodulin on endogenously catalyzed ADP-ribosylation were investigated in adipocyte plasma membranes. Four specific proteins of 70, 65, 61 and 52 kDa were labeled with [32P]ADP-ribose and ADP-ribosylation of the proteins was highly dependent upon the conditions employed. ADP-ribosylation of the 70 kDa protein was observed only in membranes supplemented with Ca2+. Maximal incorporation of [32P] into the protein was achieved with free Ca2+ concentrations of 90 microM. Calcium-stimulated ADP-ribosylation of the 70 kDa protein was inhibited by calmodulin. Half-maximal inhibition was observed in membranes incubated with 1.2 microM calmodulin. The effect of calmodulin was characterized by an inhibition of the incorporation of [32P]ADP-ribose as opposed to a stimulation of its removal. ADP-ribosylation of the 61 kDa protein was not altered by added Ca2+ and/or calmodulin whereas ADP-ribosylation of the 65 kDa protein was partially (50%) inhibited by free Ca2+ concentrations between 10(-6) - 10(-5) M. These results provide evidence that the adipocyte plasma membrane contains ADP-ribosyltransferase activities and demonstrate that ADP-ribosylation of a 70 kDa protein is regulated by Ca2+ and calmodulin.
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D008970:Molecular Weight; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D051381:Rats
chemical_list: D002147:Calmodulin; D008565:Membrane Proteins; D009702:Nucleoside Diphosphate Sugars; D000246:Adenosine Diphosphate Ribose; D004492:Edetic Acid; D002118:Calcium