title: MDC9, a widely expressed cellular disintegrin containing cytoplasmic SH3 ligand domains.
abstract: Cellular disintegrins are a family of proteins that are related to snake venom integrin ligands and metalloproteases. We have cloned and sequenced the mouse and human homologue of a widely expressed cellular disintegrin, which we have termed MDC9 (for metalloprotease/disintegrin/cysteine-rich protein 9). The deduced mouse and human protein sequences are 82% identical. MDC9 contains several distinct protein domains: a signal sequence is followed by a prodomain and a domain with sequence similarity to snake venom metalloproteases, a disintegrin domain, a cysteine-rich region, an EGF repeat, a membrane anchor, and a cytoplasmic tail. The cytoplasmic tail of MDC9 has two proline-rich sequences which can bind the SH3 domain of Src, and may therefore function as SH3 ligand domains. Western blot analysis shows that MDC9 is an approximately 84-kD glycoprotein in all mouse tissues examined, and in NIH 3T3 fibroblast and C2C12 myoblast mouse cell lines. MDC9 can be both cell surface biotinylated and 125I-labeled in NIH 3T3 mouse fibroblasts, indicating that the protein is present on the plasma membrane. Expression of MDC9 in COS-7 cells yields an 84-kD protein, and immunofluorescence analysis of COS-7 cells expressing MDC9 shows a staining pattern that is consistent with a plasma membrane localization. The apparent molecular mass of 84 kD suggests that MDC9 contains a membrane-anchored metalloprotease and disintegrin domain. We propose that MDC9 might function as a membrane-anchored integrin ligand or metalloprotease, or that MDC9 may combine both activities in one protein.
authors.affiliation: Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
authors.forename: G
authors.initials: G
authors.lastname: Weskamp
authors.forename: J
authors.initials: J
authors.lastname: Krätzschmar
authors.forename: M S
authors.initials: MS
authors.lastname: Reid
authors.forename: C P
authors.initials: CP
authors.lastname: Blobel
mesh_terms: D016475:3T3 Cells; D051722:ADAM Proteins; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D019483:Disintegrins; D006801:Humans; D008565:Membrane Proteins; D008666:Metalloendopeptidases / Q000235:genetics / Q000302:isolation & purification; D051379:Mice; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics* / Q000302:isolation & purification; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D018909:src Homology Domains
chemical_list: D018076:DNA, Complementary; D019483:Disintegrins; D008565:Membrane Proteins; D010455:Peptides; D051722:ADAM Proteins; C098339:ADAM9 protein, human; C498316:Adam9 protein, mouse; D008666:Metalloendopeptidases