title: Proteolytic cleavage of epidermal growth factor receptor. A Ca2+-dependent, sulfhydryl-sensitive proteolytic system in A431 cells.
abstract: The Mr = 160,000 epidermal growth factor (EGF) receptor in A431 cells is partially cleaved during membrane isolation to a Mr = 145,000 polypeptide containing both EGF binding and phosphate acceptor sites. We show that the proteolytic degradation of the EGF receptor depends upon the presence of Ca2+ in the medium used to scrape the cells from the substratum. Only the high molecular weight form of the receptor is detected in membranes prepared in the absence of Ca2+. Ca2+-dependent proteolysis occurs rapidly (t1/2 approximately 5 min) following cell scraping. Proteolysis results in a decrease in EGF-dependent phosphorylation of the receptor while retaining EGF binding capacity. In addition, membranes containing the uncleaved form of the receptor reveal a substantial increase in EGF-dependent phosphorylation of proteins with Mr approximately 80, 89, and 185 X 10(3). In the presence of Ca2+, addition of iodoacetic acid to the scraping medium strongly inhibits receptor fragmentation, whereas other inhibitors (phenylmethylsulfonyl fluoride, leupeptin, and pepstatin) have no effect. The results implicate a role for a Ca2+-dependent, SH-sensitive protease in EGF receptor degradation. Prevention of proteolysis yields membrane preparations with highly active EGF-dependent kinase system.
mesh_terms: D002118:Calcium / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors; D006801:Humans; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D007700:Kinetics; D010447:Peptide Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*
chemical_list: D007461:Iodoacetates; D011956:Receptors, Cell Surface; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D010447:Peptide Hydrolases; D002118:Calcium; D019807:Iodoacetic Acid