The long isoform of the cell adhesion molecule C-CAM binds to actin

C-CAM is a member of the carcinoembryonic antigen family (CEA) of the rat, which mediates cell adhesion in vitro and binds to signal transduction mole cules. In many tissues C-CAM is expressed in the apical domain of the plasm a membrane in close contact with intracellular cortical microfilaments, e.g ., in the microvilli of the brush borders of enterocytes, Regarding this su bcellular localisation, we have investigated the C-CAM interaction with the cytoskeleton. The association of C-CAM with detergent-insoluble structures increased when the small intestinal mucosa was extracted under conditions known to preserve the cytoskeleton of the brush borders. We found a coimmun oprecipitation of actin with C-CAM of the small intestine mucosa which incr eased in the presence of the chemical cross-linker DSP, allowing the demons tration of complexes between C-CAM and actin of different molecular masses, A recombinant fusion protein of the cytoplasmic domain of the long isoform of C-CAM bound specifically to purified actin in a cosedimentation assay. These results suggest an intrinsic actin-binding activity of C-CAM. (C) 199 9 Academic Press.