Subcellular localization of yeast Sec14 homologues and their involvement in regulation of phospholipid turnover.
Sec14p of the yeast Saccharomyces cerevisiae is involved in protein secretion and regulation of lipid synthesis and turnover in vivo, but acts as a phosphatidylinositol-phosphatidylcholine transfer protein in vitro. In this work, the five homologues of Sec14p, Sfh1p-Sfh5p, were subjected to biochemical and cell biological analysis to get a better view of their physiological role. We show that overexpression of SFH2 and SFH4 suppressed the sec14 growth defect in a more and SFH1 in a less efficient way, whereas overexpression of SFH3 and SFH5 did not complement sec14. Using C-terminal yEGFP fusions, Sfh2p, Sfh4p and Sfh5p are mainly localized to the cytosol and microsomes similar to Sec14p. Sfh1p was detected in the nucleus and Sfh3p in lipid particles and in microsomes. In contrast to Sec14p, which inhibits phospholipase D1 (Pld1p), overproduction of Sfh2p and Sfh4p resulted in the activation of Pld1p-mediated phosphatidylcholine turnover. Interestingly, Sec14p and the two homologues Sfh2p and Sfh4p downregulate phospholipase B1 (Plb1p)-mediated turnover of phosphatidylcholine in vivo. In summary, Sfh2p and Sfh4p are the Sec14p homologues with the most pronounced functional similarity to Sec14p, whereas the other Sfh proteins appear to be functionally less related to Sec14p.
Schnabl
Martina
M
Department of Biochemistry, University of Technology, Graz, Austria.
Oskolkova
Olga V
OV
Holic
Roman
R
Brezná
Barbara
B
Pichler
Harald
H
Zágorsek
Milos
M
Kohlwein
Sepp D
SD
Paltauf
Fritz
F
Daum
Günther
G
Griac
Peter
P
D002352:Carrier Proteins / Q000032:analysis* / Q000235:genetics / Q000502:physiology*; D005656:Fungal Proteins / Q000378:metabolism; D005816:Genetic Complementation Test; D008245:Lysophospholipase; D008565:Membrane Proteins / Q000032:analysis* / Q000235:genetics / Q000502:physiology*; D008856:Microscopy, Fluorescence; D009154:Mutation; D010641:Phenotype; D010713:Phosphatidylcholines / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis* / Q000235:genetics / Q000502:physiology*
C483430:CSR1 protein, S cerevisiae; D002352:Carrier Proteins; D005656:Fungal Proteins; D008565:Membrane Proteins; C483431:PDR16 protein, S cerevisiae; C492205:PDR17 protein, S cerevisiae; D010713:Phosphatidylcholines; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; C483438:SEC14 protein, S cerevisiae; C118289:SEC24 protein, S cerevisiae; C483439:SFH5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D008245:Lysophospholipase; C490270:PLB1 protein, S cerevisiae; D010739:Phospholipase D; C106801:phospholipase D1