The Structure and Function of the Yeast Cell Wall, Plasma Membrane and Periplasm

ABSTRACTYeast cell wall integrity (CWI) signaling serves as a model of the regulation of fungal cell wall synthesis and provides the basis for the development of antifungal drugs. A set of five membrane-spanning sensors (Wsc1 to Wsc3, Mid2, and Mtl1) detect cell surface stress and commence the signaling pathway upon perturbations of either the cell wall structure or the plasma membrane. We here summarize the latest advances in the structure/function relationship primarily of the Wsc1 sensor and critically review the evidence that it acts as a mechanosensor. The relevance and physiological significance of the information obtained for the function of the other CWI sensors, as well as expected future developments, are discussed.

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NPFXD-mediated Endocytosis Is Required for Polarity and Function of a Yeast Cell Wall Stress Sensor

Molecular Biology of the Cell ◽

10.1091/mbc.e06-08-0721 ◽

2007 ◽

Vol 18 (1) ◽

pp. 57-65 ◽

Cited By ~ 59

Author(s):

Hai Lan Piao ◽

Iara M.P. Machado ◽

Gregory S. Payne

Keyword(s):

Cell Wall ◽

Yeast Cell ◽

Wall Stress ◽

Yeast Cell Wall ◽

Stress Sensor ◽

Cell Wall Stress ◽

A Cell ◽

Increased Sensitivity ◽

Targeting Signal ◽

And Function

The actin-associated protein Sla1p, through its SHD1 domain, acts as an adaptor for the NPFX(1,2)D endocytic targeting signal in yeast. Here we report that Wsc1p, a cell wall stress sensor, depends on this signal-adaptor pair for endocytosis. Mutation of NPFDD in Wsc1p or expression of Sla1p lacking SHD1 blocked Wsc1p internalization. By live cell imaging, endocytically defective Wsc1p was not concentrated at sites of endocytosis. Polarized distribution of Wsc1p to regions of cell growth was lost in the absence of endocytosis. Mutations in genes necessary for endosome to Golgi traffic caused redistribution of Wsc1p from the cell surface to internal compartments, indicative of recycling. Inhibition of Wsc1p endocytosis caused defects in polarized deposition of the cell wall and increased sensitivity to perturbation of cell wall synthesis. Our results reveal that the NPFX(1,2)D-Sla1p system is responsible for directing Wsc1p into an endocytosis and recycling pathway necessary to maintain yeast cell wall polarity. The dynamic localization of Wsc1p, a sensor of the extracellular wall in yeast, resembles polarized distribution of certain extracellular matrix-sensing integrins through endocytic recycling.

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Yeast cell wall, membrane, and soluble marker polypeptides identified by comparative two-dimensional electrophoresis

Canadian Journal of Biochemistry ◽

10.1139/o80-077 ◽

1980 ◽

Vol 58 (7) ◽

pp. 565-572 ◽

Cited By ~ 7

Author(s):

A. J. Robertson ◽

J. H. Gerlach ◽

G. H. Rank ◽

L. C. Fowke

Keyword(s):

Cell Wall ◽

Plasma Membrane ◽

Yeast Cell ◽

Soluble Protein ◽

Protein Fractions ◽

Yeast Cells ◽

Yeast Cell Wall ◽

Total Soluble Protein ◽

Cell Wall Fraction ◽

Two Dimensional

Yeast cell wall, plasma membrane, total spheroplast, and total soluble protein fractions were isolated from exponentially growing Saccharomyces cerevisiae batch cultures. The cell wall, plasma membrane, and soluble protein fractions were obtained by mechanical disruption of intact yeast cells under identical osmotic conditions. Electron micrographs of purified wall fractions appeared free of vesicular membrane contamination and micrographs of plasma membrane vesicles were free of cell wall contamination. Various stages of cell wall purification were monitored by electron microscopy and comparative two-dimensional sodium dodecyl sulfate – polyacrylamide gel electrophoresis. This resulted in the identification of a glycopeptide designated 16 w in the cell wall fraction, with an apparent isoelectric point of 5.0 and an apparent molecular weight of 25 000. Protein analyses of soluble and plasma membrane protein fractions failed to detect component 16w. Two-dimensional protein analyses of total cellular homogenates were capable of resolving the cell wall glycopeptide 16w. However, protein separations of spheroplasts formed by glusulase degradation of the cell wall complex did not detect 16w. These observations suggest that component 16w is unique to the cell wall fraction. In addition, comparison of two-dimensional gels of soluble and plasma membrane proteins, with a total cellular homogenate, tentatively identified several polypeptides unique to each of the soluble and plasma membrane fractions.

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