Identification of a serine protease which activates the mouse heart adenosine 5',5"',P1,P4-tetraphosphate receptor.
We have previously demonstrated that a serine protease dependent processing step is required for activation of the 30-kDa adenosine 5',5"',P1,P4-tetraphosphate (Ap4A) receptor. However, monoclonal antibodies (Mabs) against a 212-kDa polypeptide inhibit Ap4A binding to its receptor [Walker et al. (1993) Biochemistry 32, 1264-1269]. SDS-PAGE followed by autoradiography of [3H]diisopropylfluorophosphate (DIPF) covalently attached to membrane fractions reveals that the serine protease is the 212-kDa polypeptide or a proenzyme. Mabs against the 30-kDa Ap4A receptor are identified that inhibit Ap4A binding to its membrane receptor. These Mabs do not recognize the 212-kDa membrane protein but recognize four membrane proteins with molecular masses of 67, 55, 42, and 30 kDa. These data suggest that the precursor for the Ap4A receptor is a 67-kDa polypeptide which undergoes multiple cleavage events, at least one by the 212-kDa protein.
Department of Biological Sciences, Clemson University, South Carolina 29634-1903.
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Walker
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Hilderman
D000818:Animals; D000911:Antibodies, Monoclonal; D001345:Autoradiography; D002462:Cell Membrane / Q000378:metabolism; D015226:Dinucleoside Phosphates / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D007531:Isoflurophate / Q000378:metabolism; D051379:Mice; D008970:Molecular Weight; D009206:Myocardium / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D018048:Receptors, Purinergic P2; D012697:Serine Endopeptidases / Q000276:immunology / Q000494:pharmacology*
D000911:Antibodies, Monoclonal; D015226:Dinucleoside Phosphates; D011956:Receptors, Cell Surface; D018048:Receptors, Purinergic P2; C080426:adenosine 5',5''',P1,P4-tetraphosphate receptor; D007531:Isoflurophate; C020733:diadenosine tetraphosphate; D012697:Serine Endopeptidases