We have identified and characterized a COOH-terminal motor domain-type kine
sin superfamily protein (KIFC), KIFC3, in the kidney. KIFC3 is a minus end-
directed microtubule motor protein, therefore it accumulates in regions whe
re minus ends of microtubules assemble. In polarized epithelial cells, KIFC
3 is localized on membrane organelles immediately beneath the apical plasma
membrane of renal tubular epithelial cells in vivo and polarized MDCK II c
ells in vitro. Flotation assay, coupled with detergent extraction, demonstr
ated that KIFC3 is associated with Triton X-100-insoluble membrane organell
es, and that it overlaps with apically transported TGN-derived vesicles. Th
is was confirmed by immunoprecipitation and by GST pulldown experiments sho
wing the specific colocalization of KIFC3 and annexin XIIIb, a previously c
haracterized membrane protein for apically transported vesicles (Lafont, F.
, S. Lecat, P. Verkade, and K. Simons. 1998. J. Cell Biol. 142:1413-1427).
Furthermore, we proved that the apical transport of both influenza hemagglu
tinin and annexin XIIIb was partially inhibited or accelerated by overexpre
ssion of motor-domain less (dominant negative) or full-length KIFC3, respec
tively. Absence of cytoplasmic dynein on these annexin XIIIb-associated ves
icles and distinct distribution of the two motors on the EM level verified
the existence of KIFC3-driven transport in epithelial cells.