ADAM12/Syndecan-4 Signaling Promotes β1Integrin-dependent Cell Spreading through Protein Kinase Cα and RhoA

Charles Kumar Thodeti, Reidar Albrechtsen, Morten Grauslund, Meena Asmar, Christer Larsson, Yoshikazu Takada, Arthur M. Mercurio, John R. Couchman, Ulla M. Wewer
2002 Journal of Biological Chemistry  
The ADAMs (a disintegrin and metalloprotease) comprise a large family of multidomain proteins with cellbinding 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 ␤ 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
more » ... 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 ␤ 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)␣ activation or a different member of the syndecan family, syndecan-2, was unable to promote cell spreading. GF109203X and Gö 6976, inhibitors of PKC, completely inhibited ADAM12/syndecan-4-induced cell spreading. Expression of syndecan-4, but not syn4⌬I, resulted in the accumulation of activated ␤ 1 integrins at the cell periphery in Chinese hamster ovary ␤1 cells as revealed by 12G10 staining. Further, expression of myristoylated, constitutively active PKC␣ resulted in ␤ 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 ␤ 1 integrin-dependent fashion through PKC␣ and RhoA, and PKC␣ and RhoA likely function in separate pathways. 1 The abbreviations used are: PKC, protein kinase C; mAb, monoclonal antibody; ADAM, a disintegrin and metalloprotease; GAG, glycosaminoglycan; EGFP, enhanced green fluorescent protein; FITC, fluorescein isothiocyanate; TRITC, tetramethylrhodamine isothiocyanate; CHO, chinese hamster ovary cells; CNF1, cytotoxic necrotizing factor 1; rADAM12-cys, recombinant ADAM12 cysteine-rich domain.
doi:10.1074/jbc.m208937200 pmid:12509413 fatcat:yhffuhwg7fecna5dl6x43hqama