The contribution of the O‐glycosylated protein Pir2p/Hsp150 to the construction of the yeast cell wall in wild‐type cells and β1,6‐glucan‐deficient mutants

Abstract

SummaryThe cell wall of yeast contains a major structural unit, consisting of a cell wall protein (CWP) attached via a glycosylphosphatidylinositol (GPI)-derived structure to ␤1,6-glucan, which is linked in turn to ␤1,3-glucan. When isolated cell walls were digested with ␤1,6-glucanase, 16% of all CWPs remained insoluble, suggesting an alternative linkage between CWPs and structural cell wall components that does not involve ␤1,6-glucan. The ␤1,6-glucanase-resistant protein fraction contained the recently identified GPI-lacking, O-glycosylated Pir-CWPs, including Pir2p/Hsp150. Evidence is presented that Pir2p/Hsp150 is attached to ␤1,3-glucan through an alkali-sensitive linkage, without ␤1,6-glucan as an interconnecting moiety. In ␤1,6-glucan-deficient mutants, the ␤1,6-glucanase-resistant protein fraction increased from 16% to over 80%. This was accompanied by increased incorporation of Pir2p/Hsp150. It is argued that this is part of a more general compensatory mechanism in response to cell wall weakening caused by low levels of ␤1,6-glucan.

Deglycosylation systematically improves N-glycoprotein identification in liquid chromatography–tandem mass spectrometry proteomics for analysis of cell wall stress responses in Saccharomyces cerevisiae lacking Alg3p

“…Gas1p is an abundant glycosyltransferase which plays a major role in cell wall remodelling during normal vegetative growth, and Δgas1 cells have a altered cell wall [49]. Hsp150p/Pir2p, a homolog of Cis3p, is upregulated in response to cell wall perturbation in response to beta 1,6-glucan deficiency [50]. In contrast, we did not detect significant changes in the expression of Hsp150p in Δalg3 cells.…”

Differential regulation of cell wall biogenesis during growth and development in yeast

“…When 1,3-β-glucan in the wall decreases, GPI-dependent cell wall proteins become linked through a direct binding of 1,6-β-glucan to chitin, which is consistent with the increased chitin availability (see Kapteyn et al, 1999a). If 1,6-β-glucan is deficient, the amount of 1,6-β-glucanase-resistant mannoproteins increases, suggesting that a larger fraction of cell wall proteins becomes incorporated by binding directly to 1,3-β-glucan and chitin (Kapteyn et al, 1999b), probably because the levels of Pir proteins increase. The third response ensures that cell wall strengthening can occur where weakening takes place.…”

“…Chitin synthesis is drastically increased, and the chitin content of cell walls, normally 1-2 %, can increase to over 20 % (reviewed by Smits et al, 1999). The transcription and incorporation of several cell wall proteins increases (de Nobel et al, 2000 ;Jung & Levin, 1999 ;Kapteyn et al, 1999b), probably to protect the glucan layer against lytic enzymes. Second, the cell switches to alternative mechanisms for incorporation of cell wall proteins.…”

Loss of Function ofKRE5Suppresses Temperature Sensitivity of Mutants Lacking Mitochondrial Anionic Lipids

“…Transcription of FKS2 is up-regulated in response to cell wall stress induced by heat, cell wall mutations, and cell wall-perturbing agents (Zhao et al, 1998;de Nobel et al, 2000;Lagorce et al, 2003;Garcia et al, 2004). Deletion of KRE5 leads to a 114-fold up-regulation of FKS2 in response to an impaired cell wall (Kapteyn et al, 1999). Restored ␤-1,3-glucan levels in pgs1⌬ mutant cells in the presence of the kre5 W1166X suppressor mutation (Table 2) could be mediated by up-regulation of FKS2 expression.…”