The docking/fusion of transport vesicles mediated by the SNARE proteins is thought to be regulated by Sec1/Munc-18 (SM) proteins. The function of SM proteins is less well understood but their importance is emphasized by the blocks of general membrane trafficking and neurotransmitter release caused by mutations in SM proteins. There are 5 members of SM genes on the C. elegans genome, in addition to
unc-18 regulating neurotransmitter release. To investigate systematically molecular structure and function of the Sec1/Munc-18 in multicellular organism, we isolated deletion mutations of all C. elegans SM proteins by TMP/UV method (K. Gengyo-Ando and S. Mitani, 2000). We are focusing on the C. elegans
vps45 (Ce-
vps45) whose orthologous protein in yeast plays an important role in membrane trafficking from the Golgi to vacuole. In the 2001 international C. elegans meeting, we reported that the putative null mutation of Ce-
vps45,
tm246, showed a maternal-effect ts larval lethal phenotype, and this phenotype was rescued when Ce-
vps45 cDNA was specifically expressed in the intestine. To visualize specific membrane trafficking pathway, we performed transgenic analyses using several fluorescent reporters in the mutant background. We found that
tm246 mutation blocked the targeting of cathepsin D/EGFP fusion protein to gut granules. These results suggested that Ce-
vps45 gene products may function in membrane trafficking from the Golgi to lysosome in mainly intestinal cells where lysosome is higy developed. Ce-
vps45 may also be required for endocytic pathway because
tm246 mutant showed a coelomocyte uptake defective (Cup) phenotype (H. Fares and I. Greenwald, 2001) in restrictive temperature. Our data demonstrate that Ce-
vps45 regulating two different membrane trafficking events in C. elegans.