Autosomal dominant polycystic kidney disease (ADPKD) affects 1 in 500 to 1000 individuals. The primary cause of the disease is associated with the defective function of polycystin-1(PC1) and polycystin-2(PC2) (1). The C. elegans homologues of PC1 and PC2 are LOV-1 and PKD-2, respectively (3), and they are localized in cilia of male-specific sensory neurons in C. elegans and required for male-mating behavior. Recently, the mammalian PC1 and PC2 have been localized to kidney primary cilia and shown to act as a mechanosensitive channel in vitro (2). The ciliary localization of polycystins is thus evolutionarily conserved between vertebrates and C. elegans. As the presence of LOV-1 and PKD-2 in sensory cilia is essential, the proper localization of human PC1 and PC2 may also be essential for function. However, the molecular mechanism of PC localization to cilia is unknown. We will use C. elegans as a model to determine the mechanism of PC localization. We are determining whether vesicular transport or intraflagellar transport (IFT) is required for the localization. Vesicular transport plays an important role in protein sorting of sensory receptors including the ODR-10 GPCR and OSM-9 TRP channel (4). IFT is an evolutionarily conserved process required for ciliogenesis(5). To begin characterization of the mechanisms of PKD-2 localization, we have examined the subcellular localization of functional PKD-2:GFP in various transport mutant backgrounds. The C. elegans gene
unc-101 encodes 1 adaptor clathrin mediating vesicular transport, and
che-3 encodes a heavy chain of cytoplasmic dynein necessary for retrograde IFT. Under the
unc-101 mutant background, PKD-2:GFP is mislocalized to dendrites of CEM neurons in adult males. The
che-3 mutant does not affect the PKD-2:GFP localization. Thus, the proper localization of PKD-2:GFP requires the AP-1 clathrin protein in vesicular transport system. We are currently examining PKD-2:GFP in other transport mutant backgrounds. We are also performing time-lapse motility assays in PKD-2:GFP transgenic animals. (1) Torres, V. D. (1998) Curr. Opin. Nephrol. Hypertens. ,7 159-69 (2) Yoder, B. K. et al. (2002) J. Am. Soc. Nephrol. 13, 2508-16 (3) Barr, M. M. & Sternberg, P. W. (1999) Nature 401, 386-89 (4) Dwyer, N. D. et al. (2001) Neuron 31, 277-87 (5) Rosenbaum, J. L. & Witman, G. B. (2002) Nat. Rev. Mol. Cell. Biol. 3, 813-25