title: Selective cleavage of the heregulin receptor ErbB-4 by protein kinase C activation.
abstract: The 180-kDa transmembrane tyrosine kinase ErbB-4 is a receptor for the growth factor heregulin. 125I-Heregulin binding to NIH 3T3 cells overexpressing the ErbB-4 receptor is rapidly decreased by 12-O-tetradecanoylphorbol-13-acetate (TPA) pretreatment. Immunologic analysis demonstrates that TPA treatment of cells induces the proteolytic cleavage of ErbB-4, producing an 80-kDa cytoplasmic domain fragment, which contains a low level of phosphotyrosine, and a 120-kDa ectodomain fragment, which is released into the extracellular medium. Cleavage of ErbB-4 was also enhanced by other protein kinase C activators, i.e. platelet-derived growth factor, ionomycin, and synthetic diacylglycerol, while protein kinase C inhibition or down-regulation suppressed the TPA stimulation of ErbB-4 degradation. TPA did not induce the degradation of related receptors (ErbB-1, ErbB-2, and ErbB-3) in the EGF receptor family. The phorbol ester-induced cleavage of ErbB-4 occurs within or close to the ectodomain, as the 80-kDa cytoplasmic domain fragment is recognized by antibody to the ErbB-4 carboxyl terminus and is membrane-associated. Coprecipitation experiments show that, while the 80-kDa ErbB-4 fragment is associated with the SH2-containing molecules PLC-gamma1 and Shc, TPA did not induce the phosphorylation of these substrates in intact cells. In addition, kinase assays in vitro indicate that the 80-kDa fragment is not an active tyrosine kinase. These results show that protein kinase C negatively regulates heregulin signaling through the ErbB-4 receptor by the activation of a selective proteolytic mechanism.
authors.affiliation: Departments of Biochemistry and Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
authors.forename: M
authors.initials: M
authors.lastname: Vecchi
authors.forename: J
authors.initials: J
authors.lastname: Baulida
authors.forename: G
authors.initials: G
authors.lastname: Carpenter
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D051379:Mice; D008970:Molecular Weight; D020890:Neuregulin-1; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D066247:Receptor, ErbB-4; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
chemical_list: D002352:Carrier Proteins; D006023:Glycoproteins; D020890:Neuregulin-1; D010446:Peptide Fragments; C087230:heregulin beta1; C587689:ERBB4 protein, human; D066246:ErbB Receptors; C587690:Erbb4 protein, mouse; D066247:Receptor, ErbB-4; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate