[
European Worm Meeting,
2006]
Johanna Pispa and Jussi Jntti. Correct regulation of protein secretion is required for many cellular processes, e.g. for the formation of cellular polarity. Consequently it needs to be tightly linked with other cellular signalling pathways. Very little is known about the molecular mechanisms that regulate this crosstalk. We are examining the interaction between the exocyst and the ER-associated protein translocation machinery in C. elegans. The exocyst is an eight-subunit complex that is required during the last stage of secretion. Its role is to tether secretory transport vesicles onto the plasma membrane. Previous work by us and others has shown that a subunit of the protein translocation complex, Sec61beta (or Seb1 in yeast) interacts both genetically and physically with the exocyst (Toikkanen et al, 2003 JBC 278:20946, Lipschutz et al., 2003 JBC 278:20954). In bacteria and yeast Sec61beta is not required for viability but in Drosophila it is (Valcrcel et al., 1999 J Cell Sci 112:4389). However, the precise function of Sec61beta is not clearly understood, and nothing is known about the significance of its interaction with the exocyst in multicellular organisms.. Our initial aim is to characterise the C. elegans Sec61beta (Y38F2AR.9). We have obtained a deletion mutant from Shohei Mitani, the National Bioresource Project, Japan. Homozygous Sec61beta worms are non-viable indicating that in multicellular animals Sec61beta is essential. Sec61beta RNAi by bacterial feeding reduces growth rate during larval development, possibly by defects in secretion of the cuticle. We have also generated worms expressing GFP-reporter constructs using Sec61beta promoter fragments of two different sizes. The longer 1.5kb promoter drives GFP expression mainly in the intestine and the pharynx. Our next goal is to analyse the Sec61beta-exocyst interactions both genetically and biochemically. For this aim we are generating antibodies against Sec61beta, and two subunits of the exocyst, Sec3 (F52E4.7) and Sec15 (C28G1.3).