title: Cellular pregnenolone esterification by acyl-CoA:cholesterol acyltransferase.
abstract: Pregnenolone (PREG) can be converted to PREG esters (PE) by the plasma enzyme lecithin: cholesterol acyltransferase (LCAT), and by other enzyme(s) with unknown identity. Acyl-CoA:cholesterol acyltransferase 1 and 2 (ACAT1 and ACAT2) convert various sterols to steryl esters; their activities are activated by cholesterol. PREG is a sterol-like molecule, with 3-β-hydroxy moiety at steroid ring A, but with much shorter side chain at steroid ring D. Here we show that without cholesterol, PREG is a poor ACAT substrate; with cholesterol, the V(max) for PREG esterification increases by 100-fold. The binding affinity of ACAT1 for PREG is 30-50-fold stronger than that for cholesterol; however, PREG is only a substrate but not an activator, while cholesterol is both a substrate and an activator. These results indicate that the sterol substrate site in ACAT1 does not involve significant sterol-phospholipid interaction, while the sterol activator site does. Studies utilizing small molecule ACAT inhibitors show that ACAT plays a key role in PREG esterification in various cell types examined. Mice lacking ACAT1 or ACAT2 do not have decreased PREG ester contents in adrenals, nor do they have altered levels of the three major secreted adrenal steroids in serum. Mice lacking LCAT have decreased levels of PREG esters in the adrenals. These results suggest LCAT along with ACAT1/ACAT2 contribute to control pregnenolone ester content in different cell types and tissues.
authors.affiliation: Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755.
authors.forename: Maximillian A
authors.initials: MA
authors.lastname: Rogers
authors.affiliation: Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755.
authors.forename: Jay
authors.initials: J
authors.lastname: Liu
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, Utah 84108; Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84112.
authors.forename: Mark M
authors.initials: MM
authors.lastname: Kushnir
authors.affiliation: Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755.
authors.forename: Elena
authors.initials: E
authors.lastname: Bryleva
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, Utah 84108; Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84112.
authors.forename: Alan L
authors.initials: AL
authors.lastname: Rockwood
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, Utah 84108; Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84112.
authors.forename: A Wayne
authors.initials: AW
authors.lastname: Meikle
authors.affiliation: Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755.
authors.forename: David
authors.initials: D
authors.lastname: Shapiro
authors.affiliation: Lipoprotein Metabolism Section,Cardiovascular-Pulmonary Branch, NHLBI, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Boris L
authors.initials: BL
authors.lastname: Vaisman
authors.affiliation: Lipoprotein Metabolism Section,Cardiovascular-Pulmonary Branch, NHLBI, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Alan T
authors.initials: AT
authors.lastname: Remaley
authors.affiliation: Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755. Electronic address: Catherine.Chang@Dartmouth.Edu.
authors.forename: Catherine C Y
authors.initials: CCY
authors.lastname: Chang
authors.affiliation: Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755. Electronic address: Ta.Yuan.Chang@Dartmouth.Edu.
authors.forename: Ta-Yuan
authors.initials: TY
authors.lastname: Chang
mesh_terms: D000101:Acetyl-CoA C-Acetyltransferase / Q000235:genetics / Q000378:metabolism*; D000311:Adrenal Glands / Q000378:metabolism; D000818:Animals; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009928:Organ Specificity / Q000502:physiology; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000235:genetics / Q000378:metabolism*; D011284:Pregnenolone / Q000235:genetics / Q000378:metabolism*; D002785:Sterol O-Acyltransferase / Q000235:genetics / Q000378:metabolism*; D000097587:Sterol O-Acyltransferase 2
chemical_list: D000101:Acetyl-CoA C-Acetyltransferase; D002784:Cholesterol; D007862:Phosphatidylcholine-Sterol O-Acyltransferase; D011284:Pregnenolone; D002785:Sterol O-Acyltransferase; D000097587:Sterol O-Acyltransferase 2; C506639:ACAT1 protein, human; C506641:Acat1 protein, mouse