INVOLVEMENT OF MICROTUBULE MOTORS IN BASOLATERAL AND APICAL TRANSPORTIN KIDNEY-CELLS

THE maintenance of a polarized cell surface requires vectorial transpo rt of vesicles to the apical and the basolateral membrane domains(1). Transport of newly synthesized apical proteins and trans-cytosis from the basolateral to the apical surface have Motors been demonstrated to depend on microtubules(2-9). In contrast, movement of membrane protei ns to the basolateral surface has been claimed to occur by diffusion a nd to be microtubule- and actin-independent(2,4,5,7,10-12). We have re -examined the role of microtubules using a recently developed polarize d transport assay in permeabilized Madin-Darby canine kidney cells(13, 14). Here we report that both apical and basolateral transport is inhi bited by nocodazole treatment. Transport to the basolateral surface wa s inhibited by immunodepletion of cytosolic kinesin. In contrast, apic al transport involved both dynein and kinesin. Our data demonstrate th at in epithelial cells, microtubule motors are involved in the movemen t of apical and basolateral vesicles. Moreover, we propose that the di fferential requirement for microtubule-based motors is related to the microtubule organization.