PROTEIN ZERO, A MYELIN IGCAM, INDUCES PHYSIOLOGICALLY OPERATIVE TIGHTJUNCTIONS IN NONADHESIVE CARCINOMA-CELLS

In the peripheral nervous system, protein zero (P-0), a hemophilic imm unoglubulin cell adhesion molecule, mediates adhesion of Schwann cell membranes as they enwrap axons and generate compact myelin. Although P o is naturally only expressed in peripheral myelin, it can behave as a vigorous adhesion molecule in a variety of cell types (Filbin et al, [1990] Nature 344:871-872; Schneider-Schaulies et al, [1990] J Neurosc i Res 27:286-297; Doyle et al, [1995] J Cell Biol 131:465-482) and can thus be characterized as an obligatory adhesion molecule, Previously, we showed that when HeLa, a cervical carcinoma cell line devoid of ep ithelial junctions, is forced to express P-0, strong cell-cell adhesio n is induced, proteins associated with junctional elements are upregul ated, and ultrastructurally tight junctions, adherens junctions, and d esmosomes become apparent (Doyle et al,, 1995), In this report, we ass essed whether the tight junctions were physiologically operative in P- 0 HeLa expressors. Consistent with the presence of operative light jun ctions, me found that P-0 expressors in monolayers maintained endogeno us proteins in their apical and basolateral plasma membrane subdomains , Furthermore, these cells generated a higher transepithelial resistan ce than did control HeLa cells, which is indicative of the formation o f an effective intercellular permeability barrier (C) 1998 Wiley-Liss, Inc.