Characterization of GPI14/YJR013w mutation that induces the cell wall integrity signalling pathway and results in increased protein production in Saccharomyces cerevisiae.

We report here identification and characterization of a mutation in the GPI14 gene, the yeast homologue of the mammalian PIG-M that functions in the synthesis of the GPI moiety anchoring proteins to the plasma membrane. We show that the first putative transmembrane domain of Gpi14p is not essential for its function. Downregulation of GPI14 expression/reduced protein function due to an amino terminal deletion resulted in increased transcription and production of an endogenous and a heterologous secreted protein expressed from HSP150 and ADH1 promoter, respectively. In these cells, unfolded protein response was induced but was not responsible for the enhanced production of these proteins. A cell wall defect in the gpi14 mutant cells was suggested by cell aggregation phenotype, increased sensitivity to Calcofluor white, an increased release of Gas1p and total protein into the culture medium. In the gpi14 mutant cells, transcription of RLM1, a transcription factor participating in the cell wall integrity signalling pathway, was increased, and deletion of RLM1 resulted in a synthetic lethal phenotype with the gpi14 mutation. These results suggest that partial inactivation of Gpi14p causes defects in the cell wall structure and suggest that compromised GPI anchor synthesis results in enhanced protein production via the cell wall integrity signalling pathway.