Integrin alpha V beta 3 is a malignant driver of anchorage-independence and tumor angiogenesis, but its dysregulation in hepatocellular carcinoma (HCC) remains unclear. In this study, we observed that sulfatide significantly promoted integrin alpha V(ITGAV) expression and wound closure in HCC. We also noted that elevated sulfatide profoundly stimulated integrin alpha V beta 3 clustering and signaling. In the cells with integrin alpha V beta 3 clustering induced by sulfatide, integrin beta 3 subunit was phosphorylated. Simultaneously, focal adhesion kinase (FAK), Src and paxillin were also phosphorylated. Treatment with FAK inhibitor resulted in robust suppression of FAK-Y397 and Src-Y416 phosphorylation stimulated by sulfatide, but not suppression of integrin beta 3 phosphorylation. Src inhibitors repressed Src-Y416 and FAK Y861 and Y925 phosphorylation, but not FAK-Y397 and integrin beta 3 phosphorylation. After mutation of integrin beta 3 (Y773F and Y785F), FAK or Src phosphorylation failed to be stimulated by sulfatide. Moreover, beta 3 Y773 and Y785 phosphorylation was suppressed by insulin-like growth factor receptor knockdown even in cells stimulated by sulfatide. In assays of immunoprecipitation and immunostaining with integrin alpha V or beta 3 antibody, labeled sulfatide was found in the complex and co-localized with integrin alpha V beta 3. Taken together, this study demonstrated that elevated sulfatide bound to integrin alpha V beta 3 and induced clustering and phosphorylation of alpha V beta 3 instead of matrix ligand binding, triggering outside-in signaling.
[1]Fudan Univ, Sch Basic Med Sci, Dept Biochem & Mol Biol, Shanghai 200433, Peoples R China.
[2]Minist Publ Hlth, Key Lab Glycoconjugate Res, Shanghai, Peoples R China.
[3]Wenzhou Med Univ, Yu Ying Childrens Hosp, Wenzhou, Peoples R China.
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