title: Epidermal growth factor (EGF) ligand release by substrate-specific a disintegrin and metalloproteases (ADAMs) involves different protein kinase C (PKC) isoenzymes depending on the stimulus.
abstract: The dysregulation of EGF family ligand cleavage has severe consequences for the developing as well as the adult organism. Therefore, their production is highly regulated. The limiting step is the ectodomain cleavage of membrane-bound precursors by one of several a disintegrin and metalloprotease (ADAM) metalloproteases, and understanding the regulation of cleavage is an important goal of current research. We have previously reported that in mouse lung epithelial cells, the pro-EGF ligands TGFα, neuregulin 1β (NRG), and heparin-binding EGF are differentially cleaved depending on the cleavage stimulus (Herrlich, A., Klinman, E., Fu, J., Sadegh, C., and Lodish, H. (2008) FASEB J.). In this study in mouse embryonic fibroblasts that lack different ADAMs, we show that induced cleavage of EGF ligands can involve the same substrate-specific metalloprotease but does require different stimulus-dependent signaling pathways. Cleavage was stimulated by phorbol ester (12-O-tetradecanoylphorbol-13-acetate (TPA), a mimic of diacylglycerol and PKC activator), hypertonic stress, lysophosphatidic acid (LPA)-induced G protein-coupled receptor activation, or by ionomycin-induced intracellular calcium release. Although ADAMs showed substrate preference (ADAM17, TGFα and heparin-binding EGF; and ADAM9, NRG), substrate cleavage differed substantially with the stimulus, and cleavage of the same substrate depended on the presence of different, sometimes multiple, PKC isoforms. For instance, classical PKC was required for TPA-induced but not hypertonic stress-induced cleavage of all EGF family ligands. Inhibition of PKCζ enhanced NRG release upon TPA stimulation, but it blocked NRG release in response to hypertonic stress. Our results suggest a model in which substantial regulation of ectodomain cleavage occurs not only on the metalloprotease level but also on the level of the substrate or of a third protein.
authors: Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA.
authors: Michelle
authors: M
authors: Dang
authors: Karen
authors: K
authors: Dubbin
authors: Antonio
authors: A
authors: D'Aiello
authors: Monika
authors: M
authors: Hartmann
authors: Harvey
authors: H
authors: Lodish
authors: Andreas
authors: A
authors: Herrlich
mesh_terms: D051722:ADAM Proteins / Q000235:genetics; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects*; D002460:Cell Line; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008024:Ligands; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D007527:Isoenzymes; D008024:Ligands; D004815:Epidermal Growth Factor; D011493:Protein Kinase C; D051722:ADAM Proteins