The WASp homologue Las17p functions with the WIP homologue End5p/verprolin and is essential for endocytosis in yeast

Abstract

Several end mutations that block the internalisation step of endocytosis in Saccharomyces cerevisiae also affect the cortical actin cytoskeleton [1]. END5 encodes a proline-rich protein (End5p or verprolin) required for a polarised cortical actin cytoskeleton and endocytosis [2,3]. End5p interacts with actin [4], but its exact function is not yet known. To help elucidate End5p function, we sought other End5p-interacting proteins and identified the LAS17/BEE1 gene (encoding the yeast homologue of the human Wiskott-Aldrich Syndrome protein, WASp) as a high-copy-number suppressor of the temperature-sensitive growth and endocytic defects of end5-1 cells (carrying a frameshift mutation affecting the last 213 residues of End5p). LAS17 is unable to suppress a full deletion of END5 (end5 delta), however, suggesting that the defective End5-1p in end5-1 mutants may be stabilised by Las17p. The amino terminus of Las17p interacts with the carboxyl terminus of End5p in the yeast two-hybrid system and similar interactions have been shown between WASp and a mammalian End5p homologue, WASp-interacting protein (WIP) [5]. As las17 delta deletion mutants are blocked in endocytosis, we conclude that Las17p and End5p interact and are essential for endocytosis.

Interaction of the Endocytic Scaffold Protein Pan1 with the Type I Myosins Contributes to the Late Stages of Endocytosis

“…Comparisons of Las17 with WASP homologues suggest that one of the mutated residues, W41E, may correspond to the invariant tryptophan residue positioned from 23 to 25 residues away from the start of WH1/EVH1 domains; this is one of the aromatic residues implicated in the WH1/EVH1 domain binding to peptide ligands (Rong and Vihinen, 2000). WH1/EVH1 domains typically bind proline-rich peptides, and the N-terminal region of Las17 that contains the WH1 domain has been reported to bind to Vrp1/End5 (Naqvi et al, 1998). It will be interesting to know whether the las17-14 mutant protein is disrupted for Vrp1 binding or Arp2/3 activation; if so, this might explain the synthetic sickness we observe with our pan1⌬PRD allele.…”

A role for yeast oxysterol-binding protein homologs in endocytosis and in the maintenance of intracellular sterol-lipid distribution

“…The percentage of faintly stained Osh-depleted cells (~85%) was similar to the wellcharacterized endocytosis mutant, las17∆ (87%), indicating a comparable defect. LAS17/BEE1 encodes the Saccharomyces cerevisiae homolog of the mammalian Wiskott-Aldrich syndrome protein, which is required for cortical actin assembly and endocytosis (Li, 1997;Naqvi et al, 1998). Although some endocytosis genes are essential, LAS17 is only required for growth at high temperatures.…”

Verprolin: A cool set of actin‐binding sites and some very HOT prolines

“…3, vrp1D 1 vector, top) (18). The end5 mutation is a frame-shift after codon 604 of VRP1 (renamed vrp1-E5) (3,18). Interestingly, vrp1-E5 retains potential function as modest over-expression of vrp1-E5 rescues vrp1D viability at 37 8C (our unpublished data).…”

“…The vrp1D cells are temperature-sensitive, that is, they are viable at 24 8C, but not at elevated temperature (e.g., 37 8C). In contrast, wild-type (VRP1) yeast cells are viable at both temperatures (2)(3)(4). The majority of vrp1D cells remain viable for a few hours and continue to grow in size at 37 8C but are unable to divide (5).…”

“…1). The verprolin-Las17p and verprolin-type I myosin complexes function in assembly of the branched F-actin that comprises actin patches and colocalise with actin patches (3,4,26,27).…”