ECM stimulated reorganization of the actin cortical mat in epithelial tissues may involve tensin, paxillin and focal adhesion kinase
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Embryonic Avian corneal epithelial tissues isolated without basal lamina (-BL) respond to extracellular matrix (ECM) molecules using an actin dependent mechanism. The basal cell surface flattens and the F-actin organizes into microfilament bundles (actin cortical mat, ACM) in the presence of laminin (LM), fibronectin (FN) or collagen (COL). The ACM had different configurations in the presence of different ECM molecules. Epithelia required contact with ECM for 15 min. for the ACM to reform in 2hrs. ACM reorganization could be blocked by phosphotyrosine (P-tyr) inhibitors, genistein and herbimycin A. Using western blot analysis, focal adhesion kinase (FAK) and paxillin (PAX) protein levels appeared the same with or without ECM, however the level of p-tyr proteins increased after 15 min. of ECM incubation. Our current goals were: 1. Determine the p-tyr changes in FAK, PAX and tensin. 2. Determine if tensin or PAX were localized to the ACM. Proteins with p-tyr residues were immunoprecipitated (using PY20) then examined by western blot analysis (FAK, PAX and tensin). Lysates were collected from epithelia isolated -BL and cultured in the presence of control media, +50 ug/ml FN, or +100ug/ml COL from 5 min. to 2hrs. The intracellular distribution of FAK, PAX and tensin showed that these proteins were localized in the cellmatrix attachment complex (CMAX). FAK, PAX, tensin and other proteins were immunoprecipitated with anti p-tyr antibodies in the presence of all ECM molecules tested. In conclusion, FAK, PAX and tensin were localized in the CMAX and were phosphorylated in embryonic epithelia.
