SLC1 and SLC4 encode partially redundant acyl-coenzyme A 1-acylglycerol-3-phosphate O-acyltransferases of budding yeast.
Phosphatidic acid is the intermediate, from which all glycerophospholipids are synthesized. In yeast, it is generated from lysophosphatidic acid, which is acylated by Slc1p, an sn-2-specific, acyl-coenzyme A-dependent 1-acylglycerol-3-phosphate O-acyltransferase. Deletion of SLC1 is not lethal and does not eliminate all microsomal 1-acylglycerol-3-phosphate O-acyltransferase activity, suggesting that an additional enzyme may exist. Here we show that SLC4 (Yor175c), a gene of hitherto unknown function, encodes a second 1-acyl-sn-glycerol-3-phosphate acyltransferase. SLC4 harbors a membrane-bound O-acyltransferase motif and down-regulation of SLC4 strongly reduces 1-acyl-sn-glycerol-3-phosphate acyltransferase activity in microsomes from slc1Delta cells. The simultaneous deletion of SLC1 and SLC4 is lethal. Mass spectrometric analysis of lipids from slc1Delta and slc4Delta cells demonstrates that in vivo Slc1p and Slc4p generate almost the same glycerophospholipid profile. Microsomes from slc1Delta and slc4Delta cells incubated with [14C]oleoyl-coenzyme A in the absence of lysophosphatidic acid and without CTP still incorporate the label into glycerophospholipids, indicating that Slc1p and Slc4p can also use endogenous lysoglycerophospholipids as substrates. However, the lipid profiles generated by microsomes from slc1Delta and slc4Delta cells are different, and this suggests that Slc1p and Slc4p have a different substrate specificity or have access to different lyso-glycerophospholipid substrates because of a different subcellular location. Indeed, affinity-purified Slc1p displays Mg2+-dependent acyltransferase activity not only toward lysophosphatidic acid but also lyso forms of phosphatidylserine and phosphatidylinositol. Thus, Slc1p and Slc4p may not only be active as 1-acylglycerol-3-phosphate O-acyltransferases but also be involved in fatty acid exchange at the sn-2-position of mature glycerophospholipids.
Department of Medicine, University of Fribourg, CH-1700 Fribourg, Switzerland.
Mohammed
M
Benghezal
Carole
C
Roubaty
Vijayanath
V
Veepuri
Jens
J
Knudsen
Andreas
A
Conzelmann
D000214:Acyl Coenzyme A / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs / Q000502:physiology; D015536:Down-Regulation / Q000502:physiology; D004398:Dyneins; D005227:Fatty Acids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D020404:Glycerophospholipids / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D050356:Lipid Metabolism / Q000502:physiology; D008246:Lysophospholipids / Q000378:metabolism; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008861:Microsomes / Q000201:enzymology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity / Q000502:physiology
D000214:Acyl Coenzyme A; D005227:Fatty Acids; D020404:Glycerophospholipids; D008246:Lysophospholipids; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; D000217:Acyltransferases; C113962:LCB4 protein, S cerevisiae; D017853:Phosphotransferases (Alcohol Group Acceptor); D004398:Dyneins; C083745:SLC1 protein, S cerevisiae; C032881:lysophosphatidic acid