title: AGPAT6 is a novel microsomal glycerol-3-phosphate acyltransferase.
abstract: AGPAT6 is a member of the 1-acylglycerol-3-phosphate O-acyltransferase (AGPAT) family that appears to be important in triglyceride biosynthesis in several tissues, but the precise biochemical function of the enzyme is unknown. In the current study, we show that AGPAT6 is a microsomal glycerol-3-phosphate acyltransferase (GPAT). Membranes from HEK293 cells overexpressing human AGPAT6 had higher levels of GPAT activity. Substrate specificity studies suggested that AGPAT6 was active against both saturated and unsaturated long-chain fatty acyl-CoAs. Both glycerol 3-phosphate and fatty acyl-CoA increased the GPAT activity, and the activity was sensitive to N-ethylmaleimide, a sulfhydryl-modifying reagent. Purified AGPAT6 protein possessed GPAT activity but not AGPAT activity. Using [(13)C(7)]oleic acid labeling and mass spectrometry, we found that overexpression of AGPAT6 increased both lysophosphatidic acid and phosphatidic acid levels in cells. In these studies, total triglyceride and phosphatidylcholine levels were not significantly altered, although there were significant changes in the abundance of specific phosphatidylcholine species. Human AGPAT6 is localized to endoplasmic reticulum and is broadly distributed in tissues. Membranes of mammary epithelial cells from Agpat6-deficient mice exhibited markedly reduced GPAT activity compared with membranes from wild-type mice. Reducing AGPAT6 expression in HEK293 cells through small interfering RNA knockdown suggested that AGPAT6 significantly contributed to HEK293 cellular GPAT activity. Our data indicate that AGPAT6 is a microsomal GPAT, and we propose renaming this enzyme GPAT4.
authors.affiliation: Lilly Research Laboratories, Eli Lilly & Company, Indianapolis, IN 46285, USA.
authors.forename: Yan Qun
authors.initials: YQ
authors.lastname: Chen
authors.forename: Ming-Shang
authors.initials: MS
authors.lastname: Kuo
authors.forename: Shuyu
authors.initials: S
authors.lastname: Li
authors.forename: Hai H
authors.initials: HH
authors.lastname: Bui
authors.forename: David A
authors.initials: DA
authors.lastname: Peake
authors.forename: Philip E
authors.initials: PE
authors.lastname: Sanders
authors.forename: Stefan J
authors.initials: SJ
authors.lastname: Thibodeaux
authors.forename: Shaoyou
authors.initials: S
authors.lastname: Chu
authors.forename: Yue-Wei
authors.initials: YW
authors.lastname: Qian
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhao
authors.forename: David S
authors.initials: DS
authors.lastname: Bredt
authors.forename: David E
authors.initials: DE
authors.lastname: Moller
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Konrad
authors.forename: Anne P
authors.initials: AP
authors.lastname: Beigneux
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Young
authors.forename: Guoqing
authors.initials: G
authors.lastname: Cao
mesh_terms: D000818:Animals; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D005227:Fatty Acids / Q000235:genetics / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007425:Intracellular Membranes / Q000201:enzymology*; D008321:Mammary Glands, Animal / Q000201:enzymology*; D051379:Mice; D008861:Microsomes / Q000201:enzymology*; D013379:Substrate Specificity / Q000502:physiology; D014280:Triglycerides / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D004791:Enzyme Inhibitors; D005227:Fatty Acids; D014280:Triglycerides; C529123:GPAT4 protein, human; D005992:Glycerol-3-Phosphate O-Acyltransferase; D005033:Ethylmaleimide