Abstract
Oxysterol-binding protein (OSBP) and its related proteins (ORPs) constitute a large and evolutionarily conserved family of lipid-binding proteins that target organelle membranes to mediate sterol signaling and/or transport. Here we characterize ORP5, a tail-anchored ORP protein that localizes to the endoplasmic reticulum. Knocking down ORP5 causes cholesterol accumulation in late endosomes and lysosomes, which is reminiscent of the cholesterol trafficking defect in Niemann Pick C (NPC) fibroblasts. Cholesterol appears to accumulate in the limiting membranes of endosomal compartments in ORP5-depleted cells, whereas depletion of NPC1 or both ORP5 and NPC1 results in luminal accumulation of cholesterol. Moreover, trans-Golgi resident proteins mislocalize to endosomal compartments upon ORP5 depletion, which depends on a functional NPC1. Our results establish the first link between NPC1 and a cytoplasmic sterol carrier, and suggest that ORP5 may cooperate with NPC1 to mediate the exit of cholesterol from endosomes/lysosomes.
Publication types
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Research Support, N.I.H., Intramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Biological Transport
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Carrier Proteins / metabolism
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Cholesterol / metabolism*
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Endoplasmic Reticulum / metabolism
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Endosomes / metabolism*
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Esterification
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Gene Knockdown Techniques
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Golgi Apparatus / metabolism
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HeLa Cells
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Humans
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Immunoprecipitation
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Intracellular Membranes / metabolism
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Intracellular Signaling Peptides and Proteins
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Lipoproteins, LDL / metabolism
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Lysosomes / metabolism
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Membrane Glycoproteins / metabolism
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Niemann-Pick C1 Protein
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Protein Binding
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Protein Structure, Tertiary
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RNA, Small Interfering / metabolism
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Receptors, Steroid / chemistry
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Receptors, Steroid / metabolism*
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Saccharomyces cerevisiae Proteins / metabolism
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Shiga Toxin / metabolism
Substances
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Carrier Proteins
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Intracellular Signaling Peptides and Proteins
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Lipoproteins, LDL
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Membrane Glycoproteins
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NPC1 protein, human
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Niemann-Pick C1 Protein
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RNA, Small Interfering
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Receptors, Steroid
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Saccharomyces cerevisiae Proteins
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TGOLN2 protein, human
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oxysterol binding protein
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Shiga Toxin
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Cholesterol