Effects of synthetic defects of very long-chain fatty acids on cell membrane stability and sensitivity of polyenes in yeast

Abstract:

[Background] Very long-chain fatty acids (VLCFA) are involved in the synthesis of membrane lipid sphingolipids and closely related to the metabolism of membrane lipid ergosterol and phospholipids. Defects in the synthesis of VLCFA in cells can damage the stability of cell membranes and thus enhance the fungal susceptibility to polyene-based drugs. However, the effect of the synthesis defects of VLCFA on the membrane stability and the sensitivity to polyene drugs is not entirely clear. [Objective] The role and function of the cell long-chain fatty acid elongases ELO1, ELO2 and ELO3. [Methods] The response of mutants with the synthesis defects of VLCFA, elo1?, elo2? and elo3?, to amphotericin B (AmB), one of the polyene drugs, and other drugs, such as nystatin (Ny) and econazole nitrate (Eco) was investigated. The ergosterol contents of different yeast cells were detected, and its response to Na+ and intracellular sodium and potassium levels was examined. [Results] We found that elo2? and elo3? mutants were highly sensitive to AmB. In addition, these two mutants were also sensitive to other drugs, such as Ny and Eco. Generally increased unsaturated fatty acids affect membrane stability. Our results showed that exogenous oleic acid (OLA) increased the sensitivity of elo2? and elo3? mutants to AmB. Compared with those of the wild-type and elo1? mutant, the ergosterol contents of the defective strains elo2? and elo3? decreased significantly. Sodium-potassium ion balance was a necessary condition for maintaining the normal physiology of cells, and was also an important parameter for measuring cell membrane stability. We found that defective strains were more sensitive to high concentrations of NaCl than wild-type strains. The levels of sodium and potassium in cells under different concentrations of AmB were detected by ICP-AES. The data showed that sodium levels were elevated in VLCFA synthesis-deficient strains compared with the wild-type strain. The potassium content in mutants was decreased significantly. [Conclusion] The synthetic defects of VLCFA could lead to the more fragile cell membrane and lower stability, thus increasing the sensitivity of fungi to polyenes. It suggests that fatty acid elongase could be the target of potential antifungal therapy.

Key words:Fatty acid elongase, Polyene drugs, Ergosterol, Sodium/Potassium ion balance, Saccharomyces cerevisiae