Abstract
Polarized traffic in epithelial cells depends on well-organized pathways that direct secretory cargo to the apical or basolateral plasma membrane. In MDCK cells, apical trafficking can be further divided into a lipid raft-dependent and a raft-independent route, which separate biosynthetic cargo in a post-Golgi endosomal compartment. We have now identified KIF5C as a kinesin motor for apical trafficking of both raft-associated sucrase isomaltase and raft-independent neurotrophin receptor. KIF5C was identified by mass spectrometry in vesicle enriched fractions and on immunoisolated post-Golgi vesicles carrying apical cargo. The amount of vesicle-associated KIF5C was highest on material isolated directly after trans-Golgi network release and declined thereafter. Altogether, our data suggest that KIF5C is involved in the passage of apical cargo molecules to a post-Golgi endosomal compartment, where further segregation into distinct vesicle populations proceeds.