title: Scavenger receptor class B type I localizes to a late endosomal compartment.
abstract: Scavenger receptor class B type I (SR-BI) has an established role in mediating the selective uptake of cholesterol from HDL in hepatocytes, steroidogenic cells, and other tissues. SR-BI is present on the plasma membrane but also localizes to stable intracellular compartments of unknown function. Using indirect immunofluorescence and subcellular fractionation, we have investigated the subcellular distribution of SR-BI. We report that red fluorescent protein-tagged mouse SR-BI (RFP-mSR-BI) colocalizes with the late endosomal and lysosomal markers, Rab7, LBPA, and Rab9. In addition, endogenous SR-BI is also found on lysosomes and colocalizes with LAMP-2 in primary hepatocytes. Furthermore, we demonstrate that the trafficking of SR-BI through these compartments is Rab7 dependent. Interestingly, filipin staining indicates accumulation of lysosomal cholesterol in SR-BI-deficient ((-/-)) as compared with wild-type hepatocytes. In addition to its role as a plasma membrane receptor, SR-BI may function in cholesterol trafficking from late endosomes/lysosomes.
authors: Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Canada K1Y 4W7.
authors: Malika
authors: M
authors: Ahras
authors: Thet
authors: T
authors: Naing
authors: Ruth
authors: R
authors: McPherson
mesh_terms: D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D008076:Cholesterol, HDL / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism*; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D051122:Scavenger Receptors, Class B / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins
chemical_list: D008076:Cholesterol, HDL; D051122:Scavenger Receptors, Class B; D000090802:rab7 GTP-Binding Proteins; C000716463:rab7 GTP-binding proteins, human; C000716465:rab7 GTP-binding proteins, mouse; D020691:rab GTP-Binding Proteins