Dissecting sensor functions in cell wall integrity signaling in Kluyveromyces lactis

Abstract

KIWSC1, KIWSC213 and KIMID2, which encode putative plasma membrane sensors for cell wall integrity signaling in Kluyveromyces lactis, were cloned and characterized. Double and triple deletion mutants show severe cell integrity defects, indicating overlapping functions. The Klwsc1 Klmid2 double deletion phenotype can be suppressed by overexpression of the downstream components K1ROM2, K1PKC1 and K1BCK1. K1Wsc1 sensor domain analyses showed that an amino-terminal elongation as well as an extension within the cytoplasmic domain are dispensable for function. Heterologous complementation by KIMID2 and K1WSC1 in Saccharomyces cerevisiae is only achieved upon overexpression. In contrast to ScMID2, ScWSCI complements in K lactis. Functional studies with chimeric Mid2 constructs indicate that species specificity is mainly conferred by the extracellular domain. Sensor-GFP fusions localize to the plasma membrane, with a cell cycle dependent distribution of KIWsc1-GFP. Both Wsc-type sensors concentrate in discrete spots within the plasma membrane. (C) 2007 Elsevier Inc. All rights reserved.