ABCA1-dependent sterol release: sterol molecule specificity and potential membrane domain for HDL biogenesis.
Mammalian cells synthesize various sterol molecules, including the C30 sterol, lanosterol, as cholesterol precursors in the endoplasmic reticulum. The build-up of precursor sterols, including lanosterol, displays cellular toxicity. Precursor sterols are found in plasma HDL. How these structurally different sterols are released from cells is poorly understood. Here, we show that newly synthesized precursor sterols arriving at the plasma membrane (PM) are removed by extracellular apoA-I in a manner dependent on ABCA1, a key macromolecule for HDL biogenesis. Analysis of sterol molecules by GC-MS and tracing the fate of radiolabeled acetate-derived sterols in normal and mutant Niemann-Pick type C cells reveal that ABCA1 prefers newly synthesized sterols, especially lanosterol, as the substrates before they are internalized from the PM. We also show that ABCA1 resides in a cholesterol-rich membrane domain resistant to the mild detergent, Brij 98. Blocking ACAT activity increases the cholesterol contents of this domain. Newly synthesized C29/C30 sterols are transiently enriched within this domain, but rapidly disappear from this domain with a half-life of less than 1 h. Our work shows that substantial amounts of precursor sterols are transported to a certain PM domain and are removed by the ABCA1-dependent pathway.
Department of Biochemistry II, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755 yyoshio@med.nagoya-u.ac.jp Ta.Yuan.Chang@Dartmouth.edu.
Yoshio
Y
Yamauchi
Nutritional Health Science Research Center and Department of Food and Nutritional Sciences, Chubu University, Kasugai 487-8501, Japan.
Shinji
S
Yokoyama
Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755 yyoshio@med.nagoya-u.ac.jp Ta.Yuan.Chang@Dartmouth.edu.
Ta-Yuan
TY
Chang
D064286:ATP Binding Cassette Transporter 1 / Q000378:metabolism*; D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism; D001692:Biological Transport; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D008076:Cholesterol, HDL / Q000096:biosynthesis* / Q000378:metabolism; D003412:Cricetulus; D004721:Endoplasmic Reticulum / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008075:Lipoproteins, HDL / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism; D051379:Mice; D002785:Sterol O-Acyltransferase / Q000378:metabolism; D013261:Sterols / Q000378:metabolism*
C577836:ABCA1 protein, human; C505693:APOA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D016632:Apolipoprotein A-I; D008076:Cholesterol, HDL; D008075:Lipoproteins, HDL; D013261:Sterols; D002784:Cholesterol; D002785:Sterol O-Acyltransferase; C493492:sterol O-acyltransferase 1
ATP binding cassette transporter A1; Niemann-Pick disease type C; acyl-CoA:cholesterol acyltransferase; cholesterol/efflux; cholesterol/trafficking; high density lipoprotein; lanosterol; lipid rafts