Zyxin and vinculin distribution at the cell-extracellular matrix attachment complex (CMAX) in corneal epithelial tissue are actin dependent

Avian embryonic corneal epithelia are two cell layers thick. If isolated wi thout (-) basal lamina, the basal cells have unorganized actin and project cytoplasmic protrusions termed blebs. The actin-based cytoskeleton at the c ell-extracellular matrix junction (termed the actin cortical mat) is disrup ted. These epithelia respond to soluble extracellular matrix molecules by r eorganizing the actin cortical mat. Sheets of epithelia were isolated + or -basal lamina. Epithelia isolated -basal lamina were cultured +/- laminin-1 and/or +/- cytochalasin D (CD), The intracellular localization of zyxin, v inculin, paxillin, focal adhesion kinase, and tensin was determined using i ndirect immunohistochemistry. Protein levels were determined by Western blo t analysis. Zyxin and vinculin were concentrated in two areas of the tissue . The interface between the upper cell layer (periderm) and the basal cells . The second area of concentration was at the inferior 1-4 microns of the b asal cells in an area with multiple actin bundles termed the actin cortical mat. The actin bundles align toward zyxin and vinculin that were located n ear basal lateral membranes. Zyxin was displaced from the basal compartment of blebbing basal cells. In contrast tensin, vinculin and focal adhesion k inase mere found diffusely throughout the blebs. Zyxin and vinculin redistr ibuted to the basal-lateral membranes as actin bundles reorganized in lamin in-stimulated epithelia. In contrast to the altered protein distribution, e xtractable protein levels were similar in blebbing and laminin-stimulated e pithelia. Zyxin, vinculin, and other associated proteins were disrupted in the GD-treated tissues and do not colocalize with each other or CD-induced actin aggregates. The intracellular localization of zyxin and vinculin were concentrated in distinct areas along the inferior basolateral membranes of basal cells termed the cell-extracellular matrix attachment complex (CMAX) . The distribution of CMAX proteins was dependent, upon actin bundle organi zation. Anat Rec 254:336-347, 1999, (C) 1999 Wiley-Liss, Inc.