The plasma membrane is the first line of cell defense against changes in external environment, thus its integrity and functionality are of utmost importance. The plasma membrane properties depend on both its protein and lipid composition. The PDR16 gene is involved in the control of Kluyveromyces lactis susceptibility to drugs and alkali metal cations. It encodes the homologue of the major K. lactis phosphatidylinositol transfer protein Sec14p. Sec14p participates in protein secretion, regulation of lipid synthesis, and turnover in vivo. We report here that the plasma membrane of the Klpdr16Δ mutant is hyperpolarized and its fluidity is lower than that of the parental strain. In addition, protoplasts prepared from the Klpdr16Δ cells display decreased stability when subjected to hypo-osmotic conditions. These changes in membrane properties lead to an accumulation of radiolabeled fluconazole and lithium cations inside mutant cells. Our results point to the fact that the PDR16 gene of K. lactis (KlPDR16) influences the plasma membrane properties in K. lactis that lead to subsequent changes in susceptibility to a broad range of xenobiotics.
Keywords: Kluyveromyces lactis; PDR16; membrane cytoplasmique; multidrug resistance; multirésistance aux médicaments; plasma membrane.