Characterization of Recombinant Human ApoB-48–Containing Lipoproteins in Rat Hepatoma McA-RH7777 Cells Transfected With ApoB-48 cDNA

Hussain, M. Mahmood; Zhao, Yang; Kancha, Ravi K.; Blackhart, Brian D.; Yao, Zemin

doi:10.1161/01.atv.15.4.485

Cited by 66 publications

(59 citation statements)

References 43 publications

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“…ApoB 19 and 20.1 also bind to TAG drops (42). ApoB 5.9, corresponding to the Nterminal b barrel, does not bind to phospholipids; however, fragments of apoB such as apoB [6][7][8][9][10][11][12][13][14][15][16][17], [6][7][8][9][10][11][12][13], etc. bind to phospholipids with different kinetics (43)(44)(45).…”

Section: Discussionmentioning

confidence: 99%

Surface study of apoB1694–1880, a sequence that can anchor apoB to lipoproteins and make it nonexchangeable

Wang

Martin

Genter

et al. 2009

Journal of Lipid Research

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Apolipoprotein B (apoB) is a nonexchangeable apolipoprotein. During lipoprotein assembly, it recruits phospholipids and triacylglycerols (TAG) into TAG-rich lipoprotein particles. It remains bound to secreted lipoproteins during lipid metabolism in plasma. The b1 region (residues 827-1880) of apoB has a high amphipathic b strand (AbS) content and is proposed to be one region anchoring apoB to lipoproteins. The AbS-rich region between apoB37 and apoB41 (residues 1694-1880) was cloned, expressed, and purified. The interfacial properties were studied at the triolein/water (TO/W) and air/water (A/W) interfaces. ApoB [37][38][39][40][41] is surface-active and adsorbs to the TO/W interface. After adsorption the unbound apoB [37][38][39][40][41] Apolipoprotein B (apoB) is a large protein (4536 residues) that plays an essential role in the formation of triacylglycerol (TAG)-rich lipoproteins by the intestine, as chylomicrons, or by the liver, as VLDL (1). The N-terminal 48% of apoB (apoB48) in the intestine and the full-length apoB (apoB100) in the liver play fundamental roles in the assembly with lipids, including phosphatidylcholine, TAG, and cholesterol, into a nascent emulsion particle which, after further modification, is secreted and ultimately enters the blood. These particles carry dietary (chylomicrons) or liver (VLDL) TAG through the blood to other tissues where they are acted upon by lipoprotein lipase to serve as a source of energy or for cell membrane and lipid droplet synthesis. ApoB is unique among apolipoproteins and a rare member of the family of proteins that bind irreversibly to lipid droplets (1, 2). Only a few other peptides share this irreversible binding, including the oleosins of oil bodies in seeds (3) and perhaps some viral core proteins such as those in hepatitis C virus (4). Oleosins and virus core proteins have a large hydrophobic, proline-rich region that has been suggested to anchor these peptides permanently to their respective emulsion particles. ApoB is the only nonexchangeable apolipoprotein: it remains with the particle from the time it is formed in the liver or intestine until it is removed and catabolized through receptor-mediated cell uptake (1, 2). All remaining plasma apolipoproteins are exchangeable, moving Abbreviations: AaH, amphipathic a helix; AbS, amphipathic beta strand; ApoB, apolipoprotein B; apoB48, N-terminal 48% of apoB; apoB100, full-length apoB; A/W, air/water; CSP, a consensus sequence peptide of exchangeable apolipoproteins; DD/W, dodecane/water; DPC, dodecylphosphocholine; GIXD, grazing incidence X-ray diffraction; HC/W, hydrocarbon/water; IDL, intermediate density lipoprotein; MTP, microsomal triglyceride transfer protein; TAG, triacylglycerol; TO/W, triolein/water.

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Section: Discussionmentioning

confidence: 99%

Surface study of apoB1694–1880, a sequence that can anchor apoB to lipoproteins and make it nonexchangeable

Wang

Martin

Genter

et al. 2009

Journal of Lipid Research

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“…ApoB and apoA-I were quantified using a sandwich ELISA (40,41). Plasma total cholesterol (Infinity TM Cholesterol, TR13421) and triglycerides (Infinity TM Triglyceride, TR22421) were measured using commercial kits (Thermo Trace, Melbourne, Australia).…”

Section: Other Methodsmentioning

confidence: 99%

Evidence for multiple complementary pathways for efficient cholesterol absorption in mice

Iqbal

Hussain

2005

Journal of Lipid Research

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Apolipoprotein B (apoB)-dependent and apoBindependent pathways for cholesterol transport have been described in cultured cells. Here, we show that the apoBindependent pathway involves apoA-I-containing high density lipoproteins (HDLs). Cholesterol secretion by the HDLs, but not by the apoB pathway, was significantly reduced in primary enterocytes isolated from chow-and cholesterolfed apoA-I ؊ / ؊ mice. These enterocytes were capable of cholesterol efflux when apoA-I was provided extracellularly. In apoA-I ؊ / ؊ mice, the absorption of a bolus of cholesterol was similar in control and apoA-I ؊ / ؊ mice fed chow or highcholesterol diet. However, short-term studies revealed that cholesterol absorption was occurring over longer lengths of the intestine, and cholesterol but not triglyceride transport to the plasma and liver in chow-and cholesterol-fed apoA-I ؊ / ؊ mice was significantly reduced. These studies indicate that in apoA-I deficiency, there is a delay in cholesterol absorption, but cholesterol is eventually absorbed because of the compensatory apoB pathway. Nonetheless, long-term studies involving multiple feedings showed significant reduction in cholesterol absorption after 4 days. We propose that multiple compensatory mechanisms ensure efficient cholesterol absorption in mice. Cholesterol absorption is defined as the transport of cholesterol from intestinal lumen to plasma (1, 2). There are three major steps in this process. The first step occurs in the lumen of the intestine and involves emulsification and hydrolysis of dietary fat and cholesteryl esters by bile acids and pancreatic enzymes. Genetic ablation of cholesteryl ester hydrolase (3) and pancreatic triglyceride lipase (4) has been shown to decrease cholesterol absorption, emphasizing their role in the hydrolysis of dietary fat in the intestinal lumen. The second step is the uptake of free cholesterol by enterocytes. Several candidate proteins that can facilitate cholesterol uptake by enterocytes have been identified. Current emerging evidence suggests that Niemann-Pick C1-like 1 (NPC1L1) might play a key role in this process. NPC1L1 gene deletion reduces cholesterol absorption in mice (5, 6). Furthermore, ezetimibe, a cholesterol absorption inhibitor, was shown to be ineffective in the absence of NPC1L1. The third step is the assembly of cholesterol and cholesteryl esters with lipoproteins in the enterocytes. The importance of apolipoprotein B (apoB) lipoproteins, mainly chylomicrons, in this process has been appreciated for a long time (7). Recently, we have provided evidence for multiple, independently regulated pathways for cholesterol transport across the intestinal epithelial cells (8). These pathways were broadly classified into apoB-dependent and apoB-independent pathways. However, it is not known whether such mechanisms play a role in cholesterol absorption in vivo. To test the hypothesis that multiple pathways contribute to efficient cholesterol absorption in vivo, we used apoA-I knockout mice as a model system.ApoA-I is the ma...

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“…Media and cells were collected in tubes containing protease inhibitors (Sigma-Aldrich). Media were centrifuged and supernatants were used to measure apoB by ELISA ( 34,35 ). Cells were used to measure intracellular apoB.…”

Section: Cell Culture and Apob Secretion Studiesmentioning

confidence: 99%

Loss of both phospholipid and triglyceride transfer activities of microsomal triglyceride transfer protein in abetalipoproteinemia

Khatun

Walsh

Hussain

2013

Journal of Lipid Research

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Characterization of Recombinant Human ApoB-48–Containing Lipoproteins in Rat Hepatoma McA-RH7777 Cells Transfected With ApoB-48 cDNA

Cited by 66 publications

References 43 publications

Surface study of apoB1694–1880, a sequence that can anchor apoB to lipoproteins and make it nonexchangeable

Surface study of apoB1694–1880, a sequence that can anchor apoB to lipoproteins and make it nonexchangeable

Evidence for multiple complementary pathways for efficient cholesterol absorption in mice

Loss of both phospholipid and triglyceride transfer activities of microsomal triglyceride transfer protein in abetalipoproteinemia

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