A novel cardiolipin-remodeling pathway revealed by a gene encoding an endoplasmic reticulum-associated acyl-CoA:lysocardiolipin acyltransferase (ALCAT1) in mouse.
Cardiolipin is a major membrane polyglycerophospholipid that is required for the reconstituted activity of a number of key mitochondrial enzymes involved in energy metabolism. Cardiolipin is subjected to remodeling subsequent to its de novo biosynthesis to attain appropriate acyl composition for its biological functions. Yet, the enzyme(s) involved in the remodeling process have not been identified. We report here the identification and characterization of a murine gene that encodes an acyl-CoA:lysocardiolipin acyltransferase 1 (ALCAT1). Expression of the ALCAT1 cDNA in either insect or mammalian cells led to a significant increase in acyl-CoA:monolysocardiolipin acyltransferase and acyl-CoA: dilysocardiolipin acyltransferase activities that exhibited a dependence upon ALCAT1 enzyme levels. The recombinant ALCAT1 enzyme recognizes both monolysocardiolipin and dilysocardiolipin as substrates with a preference for linoleoyl-CoA and oleoyl-CoA as acyl donors. In contrast, no significant increases in acyltransferase activities by the recombinant ALCAT1 were detected against either glycerol-3-phosphate or a variety of other lysophospholipids as substrates, including lysophosphatidylcholine, lysophosphatidylethanolamine, and lysophosphatidylserine. Immunocytohistochemical analysis showed that the ALCAT1 enzyme is localized in the endoplasmic reticulum, which is supported by a significant ALCAT activity in isolated liver and heart microsomes. Northern blot analysis indicates that the mouse ALCAT1 is widely distributed, with the highest expression in heart and liver. In support of a role for ALCAT1 in maintaining heart function, the ALCAT1 gene is conserved among different species of vertebrates, but not in non-atrium organisms. ALCAT1 represents the first identified cardiolipin-remodeling enzyme from any living organism; its identification implies a novel role for the endoplasmic reticulum in cardiolipin metabolism.
Cao
Jingsong
J
Endocrine Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285, USA.
Liu
Yanfang
Y
Lockwood
John
J
Burn
Paul
P
Shi
Yuguang
Y
D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002308:Cardiolipins / Q000378:metabolism*; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018411:Spodoptera; D014018:Tissue Distribution; D014162:Transfection
D002308:Cardiolipins; D018076:DNA, Complementary; D012333:RNA, Messenger; D011994:Recombinant Proteins; D000217:Acyltransferases; C018760:acyl CoA-phospholipid acyltransferase