Nonvesicular sterol transport: two protein families and a sterol sensor?
Sterols, essential components of eukaryotic membranes, are actively transported between cellular membranes. Although it is known that both vesicular and non-vesicular means are used to move sterols, the molecules and molecular mechanisms involved have yet to be identified. Recent studies point to a key role for oxysterol binding protein (OSBP) and its related proteins (ORPs) in nonvesicular sterol transport. Here, evidence that OSBP and ORPs are bona fide sterol carriers is discussed. In addition, I hypothesize that ATPases associated with various cellular activities regulate the recycling of soluble lipid carriers and that the Niemann Pick C1 protein facilitates the delivery of sterols from endosomal membranes to ORPs and/or the ensuing membrane dissociation of ORPs.
Yang
Hongyuan
H
Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 117597 Singapore. bchyangr@nus.edu.sg
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D005033:Ethylmaleimide; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000378:metabolism; D000077296:Niemann-Pick C1 Protein; D011987:Receptors, Steroid / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013261:Sterols / Q000378:metabolism*; D000098825:Oxysterol Binding Proteins
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; C106881:NPC1 protein, human; D000077296:Niemann-Pick C1 Protein; D011987:Receptors, Steroid; D013261:Sterols; D000098825:Oxysterol Binding Proteins; D000251:Adenosine Triphosphatases; D005033:Ethylmaleimide