CLONING AND LOCALIZATION OF A CONVENTIONAL KINESIN MOTOR EXPRESSED EXCLUSIVELY IN NEURONS

Kinesin is a microtubule-based motor protein involved in organelle tra nsport in neuronal and nonneuronal cells. Although a single kinesin mo tor has been thought to serve all cell types, we document here that ne urons express a second conventional kinesin heavy chain (nKHC) that is 65% identical in amino acid sequence to the ubiquitously expressed ki nesin heavy chain (uKHC). By preparing antibodies which distinguish be tween the two KHCs, we demonstrate that nKHC is a nucleotide-dependent microtubule-binding protein which partially cofractionates with membr ane organelles. Immunolocalization experiments show that nKHC is distr ibuted throughout the CNS but is highly enriched in subsets of neurons . in hippocampal neurons in culture, uKHC is distributed uniformly thr oughout the neuron, whereas nKHC is selectively concentrated in the ce ll body. These results demonstrate that mammalian neuronal tissue cont ains two conventional kinesin motors which may serve distinct function s in microtubule-based transport.