Sugar-Coated Sensors

Abstract

Budding yeasts have a rigid cell wall that the yeast must be able to remodel during vegetative growth and pheromone-induced morphogenesis. Wsc1 and Mid2 are cell surface transmembrane proteins with an O-glycosylated extracellular NH 2 -terminal domain and an intracellular COOH-terminus, which are proposed to serve as sensors for cell wall integrity. Philip and Levin showed that the cytoplasmic domains of Wsc1 and Mid2 were able to interact with Rom2 (a guanine nucleotide exchange factor for Rho1, which is crucial for cell wall remodeling) and that Wsc1 and Mid2 stimulated Rho1 activation (measured as loading of guanine triphosphate analog). The authors identified PMT2 , which encodes a protein mannosyl transferase, as a gene that yields an additive cell lysis defect in a wsc1 Δ background. Pmt2 was exclusively responsible for catalyzing the glycosylation of Mid2, and defective Mid2 glycosylation resulted in impaired Mid2 stimulation of mitogen-activated protein kinase 1 in response to pheromone. Philip, B., and Levin, D.E. (2000) Wsc1 and Mid2 are cell surface sensors for cell wall integrity signaling that act through Rom2, a guanine nucleotide exchange factor for Rho1. Mol. Cell. Biol. 21 : 271-280. [Abstract] [Full Text]