title: Phospholipid transfer protein plays a major role in the initiation of apolipoprotein B-containing lipoprotein assembly in mouse primary hepatocytes.
abstract: In this study, we tested the hypothesis that phospholipid transfer protein (PLTP) is a plausible mediator of phospholipid (PL) transfer to the N-terminal 1000 residues of apoB (apoB:1000) leading to the initiation of apoB-containing lipoprotein assembly. To this end, primary hepatocytes from wild type (WT) and PLTP knock-out (KO) mice were transduced with adenovirus-apoB:1000 with or without co-transduction with adenovirus-PLTP, and the assembly and secretion of apoB:1000-containing lipoproteins were assessed. PLTP deficiency resulted in a 65 and 72% reduction in the protein and lipid content, respectively, of secreted apoB:1000-containing lipoproteins. Particles secreted by WT hepatocytes contained 69% PL, 9% diacylglycerol (DAG), and 23% triacylglycerol (TAG) with a stoichiometry of 46 PL, 6 DAG, and 15 TAG molecules per apoB:1000. PLTP absence drastically altered the lipid composition of apoB:1000 lipoproteins; these particles contained 46% PL, 13% DAG, and 41% TAG with a stoichiometry of 27 PL, 10 DAG, and 23 TAG molecules per apoB:1000. Reintroduction of Pltp gene into PLTP-KO hepatocytes stimulated the lipidation and secretion of apoB:1000-containing lipoproteins by ∼3-fold; the lipid composition and stoichiometry of these particles were identical to those secreted by WT hepatocytes. In contrast to the WT, apoB:1000 in PLTP-KO hepatocytes was susceptible to intracellular degradation predominantly in the post-endoplasmic reticulum, presecretory compartment. Reintroduction of Pltp gene into PLTP-KO hepatocytes restored the stability of apoB:1000. These results provide compelling evidence that in hepatocytes initial recruitment of PL by apoB:1000 leading to the formation of the PL-rich apoB-containing initiation complex is mediated to a large extent by PLTP.
authors: From the Department of Medicine, Division of Gerontology, Geriatrics, and Palliative Care, Basic Sciences Section, University of Alabama, Birmingham, Alabama 35294 and.
authors: Medha
authors: M
authors: Manchekar
authors: From the Department of Medicine, Division of Gerontology, Geriatrics, and Palliative Care, Basic Sciences Section, University of Alabama, Birmingham, Alabama 35294 and.
authors: Yanwen
authors: Y
authors: Liu
authors: From the Department of Medicine, Division of Gerontology, Geriatrics, and Palliative Care, Basic Sciences Section, University of Alabama, Birmingham, Alabama 35294 and.
authors: Zhihuan
authors: Z
authors: Sun
authors: the Department of Chemistry and Physics, Coastal Carolina University, Conway, South Carolina 29528.
authors: Paul E
authors: PE
authors: Richardson
authors: From the Department of Medicine, Division of Gerontology, Geriatrics, and Palliative Care, Basic Sciences Section, University of Alabama, Birmingham, Alabama 35294 and ndashti@uabmc.edu.
authors: Nassrin
authors: N
authors: Dashti
mesh_terms: D000818:Animals; D001055:Apolipoproteins B / Q000378:metabolism*; D002478:Cells, Cultured; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D008077:Lipoproteins, LDL / Q000097:blood; D008079:Lipoproteins, VLDL / Q000097:blood; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D049294:Phospholipid Transfer Proteins / Q000502:physiology*; D061251:Primary Cell Culture; D059748:Proteolysis
chemical_list: D001055:Apolipoproteins B; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D049294:Phospholipid Transfer Proteins; C510091:phospholipid transfer protein, mouse
keywords: Apolipoprotein; Biosynthesis; Hepatocyte; Lipid; Lipoprotein; Lipoprotein Secretion; Liver; Mouse; Phospholipid
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