%0 Journal Article
%T The linkage between ¦Â1 integrin and the actin cytoskeleton is differentially regulated by tyrosine and serine/threonine phosphorylation of ¦Â1 integrin in normal and cancerous human breast cells
%A Kazuhide Takahashi
%J BMC Cell Biology
%D 2001
%I BioMed Central
%R 10.1186/1471-2121-2-23
%X The ¦Â1 integrin immunoprecipitates from either HBE or MCF-7 cells involved ¦Á-actinin while actin coprecipitated with ¦Â1 integrin from HBE cells but not from MCF-7 cells. Immunoblotting using the anti-phosphotyrosine (PY) antibody indicated the phosphorylation of ¦Â1 integrin at least at tyrosine in both cells. Dephosphorylation of ¦Â1 integrin from HBE cells by protein tyrosine phosphatase (PTP), but not by protein serine/threonine phosphatase (PP), caused dissociation of actin from ¦Â1 integrin, although dephosphorylation of it from MCF-7 cells by either PTP or PP caused association of the two proteins. In MCF-7 cells ¦Â1 integrin coprecipitated doublet of proteins having the Ca2+/calmodulin-dependent protein kinase (CaMK) II activity that was susceptible to KN-62, a specific inhibitor of CaMKII.The results suggest that ¦Â1 integrin is tyrosine phosphorylated and links with actin via ¦Á-actinin in HBE cells but prevented from linking with actin in MCF-7 cells by phosphorylation at both tyrosine and serine/threonine of ¦Â1 integrin which forms a complex with ¦Á-actinin and CaMKII. Thus the linkage formation of ¦Â1 integrin with actin may be differentially regulated by its tyrosine and serine/threonine phosphorylation in normal HBE cells and breast cancer MCF-7 cells.The integrin family of surface receptors play a critical role in many cellular processes that include cell adhesion, cell spreading, and growth signaling [1-6]. Integrins interact extracellularly with the substratum such as collagens at specific sites called focal adhesions and intracellularly with many actin-binding proteins such as ¦Á-actinin, talin, and vinculin, thereby linking these proteins with the actin cytoskeleton. Links between cell surface receptor ¦Â integrins and the actin cytoskeleton are though to be established in more than one way. Integrin binds to talin [7], which also binds to vinculin [8-10], which in turn binds to ¦Á-actinin [11,12], which then binds to actin. This constitutes a three-protein
%U http://www.biomedcentral.com/1471-2121/2/23