Circulating chylomicrons acquire molecules of apolipoproteins C and E and through interaction with endothelial lipases lose a large fraction of their triacylglycerol. These changes convert them to chylomicron remnants which bind to LDL receptors, primarily on the surfaces of liver cells, clearing them from the circulation (Redgrave 2004).Most very-low-density lipoproteins (VLDL) are converted to low-density lipoproteins (LDL) (VLDL remodeling pathway). A small fraction are taken up by VLDL receptors on extrahepatic cells, as annotated here. Clearance of LDL from the blood involves binding to LDL receptors associated with coated pits at the cell surface, forming complexes that are internalized and passed via clathrin-coated vesicles to endosomes, where they dissociate. The LDL particles move into lysosomes and are degraded while the LDL receptors are returned to the cell surface. This process occurs in most cell types but is especially prominent in hepatocytes. It plays a major role in returning cholesterol from peripheral tissues to the liver (Hobbs et al. 1990).Clearance of circulating HDL particles involves particle binding to cell-surface SR-BI receptors, particle disassembly with rlease of pre-beta HDL (Silver & Tall 2001), and uptake of the latter mediated by cell-surface CUBN:AMN complex (Kozyraki et al. 1999).VLDLR internalization plays a clinically significant role in determining the efficiency of lipoprotein clearance from the blood (Poirier et al. 2008).
Mayer, G, Nimpf, J, Benjannet, S, Poirier, S, Prat, A, Seidah, NG, Bergeron, E, Nassoury, N, Marcinkiewicz, J, Mayer, H
Hobbs, HH, Goldstein, JL, Brown, MS
Fyfe, JC, Krahe, R, Kozyraki, R, Kristiansen, M, Moestrup, SK, Aminoff, M, de la Chapelle, A, Jacobsen, C, Verroust, PJ, Cui, S, Christensen, EI, Gerdes, C
Tall, AR, Silver, DL
Redgrave, TG
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