A block of endocytosis of the yeast cell wall integrity sensors Wsc1 and Wsc2 results in reduced fitness in vivo

Abstract

The response to cell surface stress in yeast is mediated by a set of five plasma membrane sensors. We here address the relation of intracellular localization of the sensors Wsc1, Wsc2, and Mid2 to their turnover and signaling function. Growth competition experiments indicate that Wsc2 plays an important role in addition to Wsc1 and Mid2. The two Wsc sensors appear at the bud neck during cytokinesis and employ different routes of endocytosis, which govern their turnover. Whereas Wsc1 uses a clathrin-dependent NPFDD signal, Wsc2 relies on a specific lysine residue (K495). In end3 and doa4 endocytosis mutants, both sensors accumulate at the plasma membrane, and a hypersensitivity to cell wall-specific drugs and to treatment with zymolyase is observed. A haploid strain in which endocytosis of the two sensors is specifically blocked displays a reduced fitness in growth competition experiments. If the Mid2 sensor is mobilized by the addition of an endocytosis signal, it mimics the dynamic distribution of the Wsc sensors, but is unable to complement the specific growth defects of a wsc1 deletion. These data suggest that sensor distribution is not the major determinant for its specificity.

Methylglyoxal Activates the Target of Rapamycin Complex 2-Protein Kinase C Signaling Pathway in Saccharomyces cerevisiae

“…Hence, the MG-induced activation of the Pkc1-Mpk1 MAP kinase cascade occurred irrespective of the Wsc1/Mid2 pathway. Besides Wsc1/Mid2, Wsc2 and Mtl1 have also been reported to act as upstream sensors for the Pkc1-Mpk1 pathway (41,42). Therefore, we determined whether these proteins are involved in the MGinduced phosphorylation of Mpk1.…”

Atomic force microscopy – looking at mechanosensors on the cell surface

“…Fluorescence microscopy has shown that GFP-Wsc1 sensors form membrane patches, but the structure-function relationships of such clusters has long remained a mystery (Wilk et al, 2010). To address this problem, spatially resolved SMFS was used to map the distribution of single Wsc1 sensors on the surface of live S. cerevisiae (Heinisch et al, 2010b).…”

Microcompartments within the yeast plasma membrane

“…Mid2-GFP fusions appear in a punctuated, rather stable, pattern in the plasma membrane of vegetative cells, but move into the shmoo projections during the yeast mating process (Hutzler et al , 2008 ;Wilk et al , 2010 ). On the other hand, Wsc1-GFP is a highly dynamic sensor, which constantly travels through endocytosis and accumulates in the plasma membrane at sites of cell wall remodeling, i.e., in the newly forming bud and at the bud neck during cytokinesis (Piao et al , 2007 ;Wilk et al , 2010 ). With regard to the above-described lateral organization of the plasma membrane, preliminary results from the Heinisch group indicate that Mid2 (and Wsc2) may colocalize with Pma1 in the MCP network, whereas Wsc1 may reside in the MCC microcompartment (Wilk , 2010 ).…”

“…Bnr1 generates actin cables extending into the mother cell Vallen et al , 2000 ;Gao et al , 2010 ;Liu et al , 2012 Chs2 Localizes to the invaginating plasma membrane at the bud neck in the anaphase Catalytic subunit of the CSII; synthesizes the chitin disk of the primary septum Shaw et al , 1991 ;Chuang and Schekman , 1996 CWI sensors (Wsc1, Wsc2) Localize to the bud neck at anaphase Sensing of cell surface stress; signal transduction triggers new cell wall biosynthesis Wilk et al , 2010 Table 1 Proteins involved in the formation of incipient bud and the bud neck compartments.…”

“…Moreover, the CWI sensor Wsc1 accumulates in the growing bud and, later on, at the bud neck in both S. cerevisiae and K. lactis (Rodicio et al , 2008 ;Wilk et al , 2010 ). There are some striking coincidences related to the mechanism of localization of these components: i) Rho1 is apparently recruited either by its interaction with the GEF Rom2 or with PI(4,5)P 2 , with the latter also recruiting Pil1 and Lsp1, the main eisosome proteins (Yoshida et al , 2009 ;Karotki et al , 2011 ).…”