CHARACTERIZATION OF THE KIF3C NEURAL KINESIN-LIKE MOTOR FROM MOUSE

Proteins of the kinesin superfamily define a class of microtubule-depe ndent motors that play crucial roles in cell division and intracellula r transport. To study the molecular mechanism of axonal transport, a c DNA encoding a new kinesin-like protein called KIF3C was cloned from a mouse brain cDNA library. Sequence and secondary structure analysis r evealed that KIF3C is a member of the KIF3 family. Ln contrast to KIF3 A and KIF3B, Northern and Western analysis indicated that KIF3C expres sion is highly enriched in neural tissues such as brain, spinal cord, and retina. When anti-KIF3C antibodies were used to stain the cerebell um, the strongest signal came from the cell bodies and dendrites of Pu rkinje cells. Ln retina, anti-KIF3C mainly stains the ganglion cells. Immunolocalization showed that the KIF3C motor in spinal cord and scia tic nerve is mainly localized in cytoplasm. In spinal cord, the KIF3C staining was punctate; double labeling with anti-giantin and anti-KIF3 C showed a clear concentration of the motor protein in the Golgi compl ex. Staining of ligated sciatic nerves demonstrated that the KIF3C mot or accumulated at the proximal side of the ligated nerve, which sugges ts that KIF3C is an anterograde motor. Immunoprecipitation experiments revealed that KIF3C and KIF3A, but not KIF3B, were coprecipitated. Th ese data, combined with previous data from other labs, indicate that K IF3C and KIF3B are ''variable'' subunits that associate with a common KIF3A subunit, but not with each other. Together these results suggest that KIF3 family members combinatorially associate to power anterogra de axonal transport.