Lipid transporters: membrane transport systems for cholesterol and fatty acids.
Lipophilic molecules can passively diffuse across cell membranes, a process that is driven by the concentration gradient, by availability of acceptors to facilitate desorption from the bilayer, and by cellular metabolism. However, evidence has accumulated that supports the existence of specialized, protein-facilitated membrane transport systems for many lipophilic molecules. This has generated considerable debate regarding why such systems need to exist. The present review summarizes recent developments related to the membrane transport systems for cholesterol and fatty acids, which have been shown to involve structurally related proteins. General similarities of the cholesterol and fatty acid systems to other lipid transport systems (briefly discussed in the Introduction section) are highlighted in the Conclusion section. The overall aim of the present review is to illustrate why lipid transporters are needed in vivo, and how they accomplish specific functions that can not be met by lipid diffusion alone.
Department of Physiology and Biophysics, State University of New York at Stony Brook, 11794-8661, USA. NadaA@Physiology.pnb.sunysb.edu
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Abumrad
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Sfeir
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Connelly
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Coburn
D000595:Amino Acid Sequence; D001692:Biological Transport; D018955:CD36 Antigens / Q000737:chemistry / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism*; D006801:Humans; D050356:Lipid Metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D027361:Organic Anion Transporters; D011971:Receptors, Immunologic / Q000737:chemistry / Q000378:metabolism; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B; D025521:Tumor Suppressor Proteins
D018955:CD36 Antigens; D002352:Carrier Proteins; C107608:FABP7 protein, human; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D027361:Organic Anion Transporters; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; D025521:Tumor Suppressor Proteins; D002784:Cholesterol