title: ADAM12/syndecan-4 signaling promotes beta 1 integrin-dependent cell spreading through protein kinase Calpha and RhoA.
abstract: The ADAMs (a disintegrin and metalloprotease) comprise a large family of multidomain proteins with cell-binding and metalloprotease activities. The ADAM12 cysteine-rich domain (rADAM12-cys) supports cell attachment using syndecan-4 as a primary cell surface receptor that subsequently triggers beta(1) integrin-dependent cell spreading, stress fiber assembly, and focal adhesion formation. This process contrasts with cell adhesion on fibronectin, which is integrin-initiated but syndecan-4-dependent. In the present study, we investigated ADAM12/syndecan-4 signaling leading to cell spreading and stress fiber formation. We demonstrate that syndecan-4, when present in significant amounts, promotes beta(1) integrin-dependent cell spreading and stress fiber formation in response to rADAM12-cys. A mutant form of syndecan-4 deficient in protein kinase C (PKC)alpha activation or a different member of the syndecan family, syndecan-2, was unable to promote cell spreading. GF109203X and Gö6976, inhibitors of PKC, completely inhibited ADAM12/syndecan-4-induced cell spreading. Expression of syndecan-4, but not syn4DeltaI, resulted in the accumulation of activated beta(1) integrins at the cell periphery in Chinese hamster ovary beta1 cells as revealed by 12G10 staining. Further, expression of myristoylated, constitutively active PKCalpha resulted in beta(1) integrin-dependent cell spreading, but additional activation of RhoA was required to induce stress fiber formation. In summary, these data provide novel insights into syndecan-4 signaling. Syndecan-4 can promote cell spreading in a beta(1) integrin-dependent fashion through PKCalpha and RhoA, and PKCalpha and RhoA likely function in separate pathways.
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: Reidar
authors.initials: R
authors.lastname: Albrechtsen
authors.forename: Morten
authors.initials: M
authors.lastname: Grauslund
authors.forename: Meena
authors.initials: M
authors.lastname: Asmar
authors.forename: Christer
authors.initials: C
authors.lastname: Larsson
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Takada
authors.forename: Arthur M
authors.initials: AM
authors.lastname: Mercurio
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; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D016466:CHO Cells; D002448:Cell Adhesion; D002465:Cell Movement; D006224:Cricetinae; D003545:Cysteine / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D019012:Integrin beta1 / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D008954:Models, Biological; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D017434:Protein Structure, Tertiary; D051381:Rats; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014162:Transfection; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D018076:DNA, Complementary; D019012:Integrin beta1; D008565:Membrane Proteins; D009124:Muscle Proteins; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D051722:ADAM Proteins; D000072199:ADAM12 Protein; C000606480:ADAM12 protein, human; C096115:Adam12 protein, mouse; D008666:Metalloendopeptidases; D020742:rhoA GTP-Binding Protein; D003545:Cysteine