Disruption of PMR1, encoding a Ca2+-ATPase homolog in Yarrowia lipolytica, affects secretion and processing of homologous and heterologous proteins.

The Yarrowia lipolytica PMR1 gene (YlPMR1) is a Saccharomyces cerevisiae PMR1 homolog which encodes a putative secretory pathway Ca2+-ATPase. In this study, we investigated the effects of a YlPMR1 disruption on the processing and secretion of native and foreign proteins in Y. lipolytica and found variable responses by the YlPMR1-disrupted mutant depending on the protein. The secretion of 32-kDa mature alkaline extracellular protease (AEP) was dramatically decreased, and incompletely processed precursors were observed in the YlPMR1-disrupted mutant. A 36- and a 52-kDa premature AEP were secreted, and an intracellular 52-kDa premature AEP was also detected. The acid extracellular protease activity of the YlPMR1-disrupted mutant was increased by 60% compared to that of the wild-type strain. The inhibitory effect of mutations in secretory pathway Ca2+-ATPase genes on the secretion of rice alpha-amylase was also observed in the Y. lipolytica and S. cerevisiae PMR1-disrupted mutants. Unlike rice alpha-amylase, the secretion of Trichoderma reesei endoglucanase I (EGI) was not influenced by the YlPMR1 disruption. However, the secreted EGI from the YlPMR1-disrupted mutant had different characteristics than that of the control. While wild-type cells secreted the hyperglycosylated form of EGI, hyperglycosylation was completely absent in the YlPMR1-disrupted mutant. Our results indicate that the effects of the YlPMR1 disruption as manifested by the phenotypic response depend on the characteristics of the reporter protein in the recombinant yeast strain evaluated.