lov-1 and
pkd-2 are required for C. elegans male mating behavior. These genes act in the same pathway and are required for response and location of vulva (Lov) aspects of mating 1,2 . LOV-1 and PKD-2 are both found exclusively in the male chemosensory neurons (CEMs, rays, hook) where they localize to sensory cilia, suggesting a role in sensory signal transduction.
lov-1 and
pkd-2 are similar to the human polycystic kidney disease (PKD) genes PKD1 and PKD2, respectively. Mutations in either PKD1 or PKD2 account for 95% of all autosomal dominant PKD cases (ADPKD). ADPKD is an extremely prevalent genetic disease, occurring in roughly 1 of every 800 persons. LOV-1, like polycystin-1 (encoded by PKD1), is a large and complex protein. LOV-1 is composed of 3178 amino acids and is predicted to contain a variety of functional domains. The extracellular amino terminus contains a mucin-like serine/threonine rich region, a number of glycosylation sites, and a G-protein coupled receptor proteolysis site (GPS) near the first putative transmembrane domain (TM1). Just after TM1 is a region of conserved homology with the lipoxygenase and alpha-toxin proteins called the PLAT/LH2 domain. Typically these domains regulate the interaction between the enzyme and plasma membrane associated proteins and lipids 3 . Following the LOV-1 PLAT/LH2 domain are 10 hydrophobic regions. The last six of these comprise a region of homology conserved in all polycystins. These six putative TM domains are related to those found in a variety of channel proteins. Polycystin-2 is comprised primarily of these 6 conserved TM domains and appears to be a calcium permeable channel 4,5 . A physical interaction between the carboxy termini of polycystin-1 and polycystin-2 is required to produce a functional channel 6 . The current model for polycystin function is that polycystin-1 is an extracellular sensor that mediates calcium flux through the polycystin-2 channel 7,8 . Likewise, we speculate that LOV-1 acts as a receptor that regulates PKD-2. Our main objective is to use in vivo experimental approaches to test if these structural and functional predictions for the polycystins are true. My first goal is to determine the overall membrane topology of LOV-1. That is, I will determine where the amino and carboxyl tail of LOV-1 is found relative to the plasma membrane. I will also determine which of the 11 hydrophobic regions found in the LOV-1 sequence are functional transmembrane spanning domains. My second goal is to determine whether the LOV-1 protein is cleaved at the GPS and to test whether the PLAT/LH2 domain is required for LOV-1 membrane localizaton and protein function. Ultimately, I will characterize calcium channel activity in vivo . By using C. elegans as a model system for ADPKD, we may begin to understand the physiological function(s) of the polycystins. 1. Barr, M. M., Demodena, J., Hall, D. H., Braun, D. & Sternberg, P. W. Nat Genet submitted . 2. Barr, M. M. & Sternberg, P. W. Nature 401 , 386-9. (1999). 3. Miled, N. et al. Biochimie 82 , 973-86. (2000). 4. Gonzalez-Perrett, S. et al. Proc Natl Acad Sci U S A 98 , 1182-1187 (2001). 5. Vassilev, P. M. et al. Biochem Biophys Res Commun 282 , 341-50. (2001). 6. Hanaoka, K. et al. Nature 408 , 990-4. (2000). 7. Calvet, J. P. & Grantham, J. J. Semin Nephrol 21 , 107-123. (2001). 8. Grantham, J. J. & Calvet, J. P. Proc Natl Acad Sci U S A 98 , 790-792. (2001).