PDR16 and PDR17, Two Homologous Genes ofSaccharomyces cerevisiae, Affect Lipid Biosynthesis and Resistance to Multiple Drugs

H Bart Van Den Hazel,Harald Pichler,Maria Adelaide Do Valle Matta,Erich Leitner,André Goffeau,Günther Daum

doi:10.1074/jbc.274.4.1934

Abstract

The Saccharomyces cerevisiae open reading frame YNL231C was recently found to be controlled by the multiple drug resistance regulator Pdr1p. Here we characterize YNL231C (PDR16) and its homologue YNL264C (PDR17). Deletion of PDR16 resulted in hypersensitivity of yeast to azole inhibitors of ergosterol biosynthesis. While no increase in drug sensitivity was found upon deletion of PDR17 alone, a Deltapdr16,Deltapdr17 double mutant was hypersensitive to a broad range of drugs. Both mutations caused significant changes of the lipid composition of plasma membrane and total cell extracts. Deletion of PDR16 had pronounced effects on the sterol composition, whereas PDR17 deletion mainly affected the phospholipid composition. Thus, Pdr16p and Pdr17p may regulate yeast lipid synthesis like their distant homologue, Sec14p. The azole sensitivity of the PDR16-deleted strain may be the result of imbalanced ergosterol synthesis. Impaired plasma membrane barrier function resulting from a change in the lipid composition appears to cause the increased drug sensitivity of the double mutant strain Deltapdr16,Deltapdr17. The uptake rate of rhodamine-6-G into de-energized cells was shown to be almost 2-fold increased in a Deltapdr16,Deltapdr17 strain as compared with wild-type and Deltapdr5 strains. Collectively, our results indicate that PDR16 and PDR17 control levels of various lipids in various compartments of the cell and thereby provide a mechanism for multidrug resistance unrecognized so far.

Highlights

The yeast Saccharomyces cerevisiae has, like many other organisms, the ability to acquire multiple drug resistance, i.e. become less sensitive to a broad range of chemically and func
Drug Sensitivity of Strains Deleted for PDR16 and/or Its Homologue PDR17—We recently identified PDR16 (YNL231C) as one of several novel genes controlled by the yeast multiple drug resistance regulator Pdr1p
To investigate whether PDR16 like other Pdr1p targets is involved in multiple drug

Summary

Introduction

The yeast Saccharomyces cerevisiae has, like many other organisms, the ability to acquire multiple drug resistance, i.e. become less sensitive to a broad range of chemically and func-. Neither Pdr1p or Pdr3p nor the drug efflux pumps which they regulate are required for growth of yeast in the absence of drugs It is not known whether the true physiological function of these drug resistance determinants is to protect the cell from external toxic compounds or whether they may play other roles. In order to get more insight into the physiological role of Pdr1p, we recently screened for target genes regulated by this transcription factor This screening resulted in the identification of a broad range of novel Pdr1p target genes, one of which was the open reading frame with the systematic name YNL231C (PDR16). The Pdr16p is 23% identical and 54% similar to the product of the S. cerevisiae SEC14 gene This homology is spread throughout the protein sequence. It was suggested that Sec14p/PITP may regulate formation of secretory vesicles from the Golgi by stimulating the turnover of phospholipids

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