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Vol. 18, Issue 1, 57-65, January 2007

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

Hai Lan Piao^*, Iara M.P. Machado^*,, and Gregory S. Payne

Department of Biological Chemistry, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA 90095

Submitted August 17, 2006; Revised September 22, 2006; Accepted October 16, 2006
Monitoring Editor: Benjamin Glick

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.

* These authors contributed equally to this work.

Present address: Departamento de Farmacia, Universidade Federal do Parana, R Lothario Meissner 3400, 80210-170 Curitiba, PR, Brazil.

Address correspondence to: Gregory S. Payne (gpayne{at}mednet.ucla.edu)

Abbreviations used: CCV, clathrin-coated vesicles; GFP, green fluorescence protein; LatA, latrunculin A; SHD1, Sla1 homology domain 1; TGN, trans-Golgi network.