title: par-1, atypical pkc, and PP2A/B55 sur-6 are implicated in the regulation of exocyst-mediated membrane trafficking in Caenorhabditis elegans.
abstract: The exocyst is a conserved protein complex that is involved in tethering secretory vesicles to the plasma membrane and regulating cell polarity. Despite a large body of work, little is known how exocyst function is controlled. To identify regulators for exocyst function, we performed a targeted RNA interference (RNAi) screen in Caenorhabditis elegans to uncover kinases and phosphatases that genetically interact with the exocyst. We identified seven kinase and seven phosphatase genes that display enhanced phenotypes when combined with hypomorphic alleles of exoc-7 (exo70), exoc-8 (exo84), or an exoc-7;exoc-8 double mutant. We show that in line with its reported role in exocytotic membrane trafficking, a defective exoc-8 caused accumulation of exocytotic soluble NSF attachment protein receptor (SNARE) proteins in both intestinal and neuronal cells in C. elegans. Down-regulation of the phosphatase protein phosphatase 2A (PP2A) phosphatase regulatory subunit sur-6/B55 gene resulted in accumulation of exocytic SNARE proteins SNB-1 and SNAP-29 in wild-type and in exoc-8 mutant animals. In contrast, RNAi of the kinase par-1 caused reduced intracellular green fluorescent protein signal for the same proteins. Double RNAi experiments for par-1, pkc-3, and sur-6/B55 in C. elegans suggest a possible cooperation and involvement in postembryo lethality, developmental timing, as well as SNARE protein trafficking. Functional analysis of the homologous kinases and phosphatases in Drosophila median neurosecretory cells showed that atypical protein kinase C kinase and phosphatase PP2A regulate exocyst-dependent, insulin-like peptide secretion. Collectively, these results characterize kinases and phosphatases implicated in the regulation of exocyst function, and suggest the possibility for interplay between the par-1 and pkc-3 kinases and the PP2A phosphatase regulatory subunit sur-6 in this process.
authors.affiliation: Institute of Biotechnology, Research Program in Cell and Molecular Biology, 00014 University of Helsinki, Helsinki, Finland.
authors.forename: Yaming
authors.initials: Y
authors.lastname: Jiu
authors.forename: Kiran
authors.initials: K
authors.lastname: Hasygar
authors.forename: Lois
authors.initials: L
authors.lastname: Tang
authors.forename: Yanbo
authors.initials: Y
authors.lastname: Liu
authors.forename: Carina I
authors.initials: CI
authors.lastname: Holmberg
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Bürglin
authors.forename: Ville
authors.initials: V
authors.lastname: Hietakangas
authors.forename: Jussi
authors.initials: J
authors.lastname: Jäntti
mesh_terms: D000483:Alleles; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005089:Exocytosis; D009154:Mutation; D010641:Phenotype; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D050600:SNARE Proteins / Q000235:genetics / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins; C409406:PAR-1 protein, C elegans; D017346:Protein Serine-Threonine Kinases; C115015:PKC-3 protein; D011493:Protein Kinase C; D054648:Protein Phosphatase 2; C489811:SUR-6 protein, C elegans
keywords: Caenorhabditis elegans; PP2A; exocyst; par-1; pkc-3