EVIDENCE FOR KINESIN-RELATED PROTEINS ASSOCIATED WITH THE AXONEME OF RETINAL PHOTORECEPTORS

Situated at the junction between inner and outer segment, the connecti ng cilium of retinal photoreceptors supports regulated transport of mo lecules that function distally, while restricting diffusion of membran e proteins from one plasmalemmal domain to the other. Both functions a re thought to be performed by a group of proteins stably or transientl y associated with the axoneme. We have identified two types of unique polypeptides which associated with the axoneme in a nucleotide-depende nt manner: they bind to the axonemes in the presence of adenosine mono phosphate (AMP)-PNP, and are solubilized in the presence of adenosine triphosphate (ATP). The first group contained glyconjugates, previousl y shown to be part of the axoneme-plasmalemma cross-linkers at the con necting cilium. The second group cross-reacted with antibodies to two different conserved peptide sequences (called LAGSE and HIPYR) of kine sin-related proteins, and included polypeptides of similar to 85-97 kD a, Immunofluorescence microscopy of whole-mounted axonemes with the tw o anti-kinesin antibodies showed labeling throughout the axoneme, incl uding the connecting cilium-basal body region. These results suggest t hat the identified proteins may serve as motor molecules for transport of material to the outer segment via the connecting cilium. (C) 1997 Academic Press Limited.