Characterization of a novel C-kinesin (KIFC3) abundantly expressed in vertebrate retina and RPE

Many forms of intracellular transport are mediated by microtubule-dependent motors of the kinesin superfamily (KIFs). To identify kinesins expressed in human retina and RPE, we used degenerate primer RT-PCR to amplify a approximately 440 bp kinesin motor domain fragment from human retinal and RPE messenger RNAs. Four distinct kinesins were detected: one C-kinesin (HsKIFC3); one kinesin from the unc104/KIF1 family [HsKIF1A]; and the ubiquitous and neuronal forms of conventional kinesin heavy chain [HsuKHC and HsnKHC]. The C-kinesin HsKIFC3 comprised 33.3% of the retinal clones and was 60% identical to FKIF2, the most abundant kinesin detected in a previous screen of fish retina and 95% identical to a fragment of MmKifC3 recently amplified from mouse brain. Elsewhere we have reported the sequence of HsKIFC3 and shown that it maps to the same locus on chromosome 16q13-q21 as Bardet-Biedl syndrome Type II, a hereditary retinal degeneration. We describe here the kinesin PCR screen of human retina and RPE and examine the tissue and subcellular distribution of KIFC3 in both fish and human retina using an antibody raised against a peptide conserved between FKIF2 and HsKIFC3. This peptide antibody identified a single approximately 80 kDa band in Western blots of fish and human retina and RPE. In both fish and human retina this antibody strongly labeled photoreceptor terminals in the outer plexiform layer, suggesting that FKIF2/KIFC3 may play some role in the photoreceptor synapse.