The alpha 7 integrin as a target protein for cell surface mono-ADP-ribosylation in muscle cells.
A membrane-associated arginine-specific mono-ADP-ribosyltransferase was purified 215,000-fold from rabbit skeletal muscle and its gene was isolated from a skeletal muscle cDNA library. The enzyme was a glycosylphosphatidyl-inositol-linked protein, present on the surface of differentiated skeletal muscle myoblasts (myotubes). Following incubation of cultured, intact myotubes with [adenylate-32P]NAD and analysis by SDS-PAGE, a major radiolabeled protein of 97/140 kDa (reduced/nonreduced conditions) was observed. It was identified as integrin alpha 7 based on its size, binding to a laminin affinity column, immunoprecipitation with a monoclonal antibody, and partial amino acid sequencing. Since ADP-ribosylarginine hydrolase, the enzyme responsible for cleavage of the ADP-ribosylarginine bond and a component with the transferase of a putative ADP-ribosylation cycle, is cytosolic, whereas the transferase is attached via a GPI-anchor to the cell surface, the processing of ADP-ribosylated integrin alpha 7 was investigated. 32P label was rapidly removed from [32P]ADP-ribosylated integrin alpha 7, a process inhibited by free ADP-ribose or p-nitrophenylthymidine-5'-monophosphate, alternative substrates for 5'-nucleotide phosphodiesterase. The processed integrin alpha 7 was not susceptible to subsequent ADP-ribosylation, although the amount of surface integrin alpha 7 remained constant. During the processing, no loss of label was observed from integrin alpha 7 radiolabeled with [14C]NAD, containing 14C in the nicotinamide-proximal ribose, consistent with a degradation of the ADP-ribose moiety by a cell surface 5'-nucleotide phosphodiesterase. Thus, cell surface ADP-ribosylation, in contrast to intracellular ADP-ribosylation, is not readily reversed by the presently known ADP-ribosylarginine hydrolase and seems to operate outside the postulated ADP-ribosylation cycle.
Zolkiewska
A
A
Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1434, USA.
Moss
J
J
D036002:ADP Ribose Transferases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D039001:Integrin alpha Chains; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D011499:Protein Processing, Post-Translational
D015703:Antigens, CD; D039001:Integrin alpha Chains; C085725:integrin alpha7; D000246:Adenosine Diphosphate Ribose; D036002:ADP Ribose Transferases