POLARIZED EXPRESSION OF HD1 - RELATIONSHIP WITH THE CYTOSKELETON IN CULTURED HUMAN COLONIC-CARCINOMA CELLS

Hemidesmosomes (HDs) mediate adhesion of epithelial cells to the extra cellular matrix and have morphological associations with intermediate- size filaments (Ifs). Hemidesmosomal molecular components including HD 1, the two bullous pemphigoid antigens, and the integrin alpha 6 beta 4 have been identified in HDs of stratified and complex epithelium. In this study, we report that HT29-Fu cells, a human colonic tumor cell line, express two hemidesmosomal components (HD1, alpha 6 beta 4) asso ciated in an adhesion structure termed type II HDs. Immunofluorescence studies showed a colocalization of HD1 and alpha 6 beta 4 in basal pa tches between actin stress fibers. Using cytochalasin B or vinblastine , two drugs which disrupt the cytoskeleton, we demonstrate that the re distribution of HD1 was probably induced by the reorganization of the basal cytokeratin network. We also show that in vitro HD1 binds to pol ymerized cyto keratin intermediate filaments; this suggests that HD1 i n intestinal epithelial cells functions as a linker protein connecting cytokeratin filaments to the basal plasma membrane, probably through the beta 4 subunit of the integrin alpha 6 beta 4. (C) 1997 Academic P ress.