title: Hierarchy of ADAM12 binding to integrins in tumor cells.
abstract: ADAMs (a disintegrin and metalloprotease) comprise a family of cell surface proteins with protease and cell-binding activities. Using different forms and fragments of ADAM12 as substrates in cell adhesion and spreading assays, we demonstrated that alpha9beta1 integrin is the main receptor for ADAM12. However, when alpha9beta1 integrin is not expressed--as in many carcinoma cells--other members of the beta1 integrin family can replace its ligand binding activity. In attachment assays, the recombinant disintegrin domain of ADAM12 only supported alpha9 integrin-dependent tumor cell attachment, whereas full-length ADAM12 supported attachment via alpha9 integrin and other integrin receptors. Cells that attached to full-length ADAM12 in an alpha9 integrin-dependent manner also attached to ADAM12 in which the putative alpha9beta1 integrin-binding motif in the disintegrin domain had been mutated. This attachment was mediated through use of an alternate beta1 integrin. We also found that cell spreading in response to ADAM12 is dependent on the apparent level of integrin activation. Binding of cells to ADAM12 via the alpha9beta1 integrin was Mn(2+)-independent and resulted in attachment of cells with a rounded morphology; attachment of cells with a spread morphology required further activation of the alpha9beta1 integrin. We demonstrated that phosphoinositide-3-kinase appears to be central in regulating alpha9beta1 integrin cell spreading activity in response to ADAM12.
authors.affiliation: Institute of Molecular Pathology, University of Copenhagen, Frederik V's vej 11, DK-2100 Copenhagen, Denmark.
authors.forename: Charles Kumar
authors.initials: CK
authors.lastname: Thodeti
authors.forename: Camilla
authors.initials: C
authors.lastname: Fröhlich
authors.forename: Christian Kamp
authors.initials: CK
authors.lastname: Nielsen
authors.forename: Peter
authors.initials: P
authors.lastname: Holck
authors.forename: Christina
authors.initials: C
authors.lastname: Sundberg
authors.forename: Marie
authors.initials: M
authors.lastname: Kveiborg
authors.forename: Yashithra
authors.initials: Y
authors.lastname: Mahalingam
authors.forename: Reidar
authors.initials: R
authors.lastname: Albrechtsen
authors.forename: John R
authors.initials: JR
authors.lastname: Couchman
authors.forename: Ulla M
authors.initials: UM
authors.lastname: Wewer
mesh_terms: D051722:ADAM Proteins; D000072199:ADAM12 Protein; D000818:Animals; D016466:CHO Cells; D002448:Cell Adhesion / Q000502:physiology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D004285:Dogs; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D017434:Protein Structure, Tertiary; D051381:Rats
chemical_list: D016023:Integrins; D008565:Membrane Proteins; C113256:integrin alpha 9 beta 1; D019869:Phosphatidylinositol 3-Kinases; D051722:ADAM Proteins; D000072199:ADAM12 Protein; C000606480:ADAM12 protein, human; D008666:Metalloendopeptidases