ИСТИНА

LAM genes encode membrane-associated sterol-binding proteins which transport sterols between the endoplasmic reticulum (ER) and the adjacent membranes. LAM proteins are found in most eukaryotic organisms, including humans, they contain transmembrane and ergosterol-binding domains. In yeast Saccharomyces cerevisiae, LAM family is represented by three pairs of paralogs. Lam1 - Lam4 proteins are localized in the endoplasmic reticulum/plasma membrane contact sites and transport sterols between these compartments. As the functions of paralogous genes are often redundant, only a few phenotypes associated with the delitions of LAM genes was reported. Here we screened for phenotypes of double and quadruple deletants of paralogous LAM2/LAM4 and LAM1/LAM3 genes encoding the ERbound proteins. We found that deletion of LAM genes does not affect yeast growth in YPD but decrease their survival in stressful conditions. For instance, double deletion of LAM2 and LAM4 genes sensibilized yeast cells to heat shock, ethanol and high osmolarity. We found that the decrease of osmolarity tolerance is not mediated by inhibition of HOG-signaling pathway. We also determined the types of genetic interactions of LAM genes within paralogous pairs and between LAM2 and some genes of ergosterol biosynthesis pathway. Our and previously reported data suggest that sterol content of plasma membrane is critically important to cell survival. We suggest that the role of LAM genes is to rapidly change plasma membrane sterol content to specific stresses. This work was supported by RSCF grant 18-14-00151.