Publications

• Phospholipid transfer activity of microsomal triacylglycerol transfer protein is sufficient for the assembly and secretion of apolipoprotein B lipoproteins.

  Rava P., Ojakian G.K., Shelness G.S., Hussain M.M.

  Human microsomal triacylglycerol transfer protein (hMTP) is essential for apolipoprotein B (apoB)-lipoprotein assembly and secretion and is known to transfer triacylglycerols, cholesterol esters, and phospholipids. To understand the relative importance of each lipid transfer activity, we compared ... >> More

  Human microsomal triacylglycerol transfer protein (hMTP) is essential for apolipoprotein B (apoB)-lipoprotein assembly and secretion and is known to transfer triacylglycerols, cholesterol esters, and phospholipids. To understand the relative importance of each lipid transfer activity, we compared the ability of hMTP and its Drosophila ortholog (dMTP) to assemble apoB lipoproteins and to transfer various lipids. apoB48 secretion was induced when co-expressed with either hMTP or dMTP in COS cells, and oleic acid supplementation further augmented secretion without altering particle density. C-terminal epitope-tagged dMTP (dMTP-FLAG) facilitated the secretion of apoB polypeptides in the range of apoB48 to apoB72 but was approximately 50% as efficient as hMTP-FLAG. Comparison of lipid transfer activities revealed that although phospholipid transfer was similar in both orthologs, dMTP was unable to transfer neutral lipids. We conclude that the phospholipid transfer activity of MTP is sufficient for the assembly and secretion of primordial apoB lipoproteins and may represent its earliest function evolved for the mobilization of lipid in invertebrates. Identification of MTP inhibitors, which selectively affect transfer of a specific lipid class, may have therapeutic potential. << Less

  J. Biol. Chem. 281:11019-11027(2006) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Cholesteryl ester transfer proteins from different species do not have equivalent activities.

  Morton R.E., Izem L.

  Site-specific changes in the amino acid composition of human cholesteryl ester transfer protein (CETP) modify its preference for triglyceride (TG) versus cholesteryl ester (CE) as substrate. CETP homologs are found in many species but little is known about their activity. Here, we examined the lip ... >> More

  Site-specific changes in the amino acid composition of human cholesteryl ester transfer protein (CETP) modify its preference for triglyceride (TG) versus cholesteryl ester (CE) as substrate. CETP homologs are found in many species but little is known about their activity. Here, we examined the lipid transfer properties of CETP species with 80-96% amino acid identity to human CETP. TG/CE transfer ratios for recombinant rabbit, monkey, and hamster CETPs were 1.40-, 1.44-, and 6.08-fold higher than human CETP, respectively. In transfer assays between VLDL and HDL, net transfers of CE into VLDL by human and monkey CETPs were offset by equimolar net transfers of TG toward HDL. For hamster CETP this process was not equimolar but resulted in a net flow of lipid (TG) into HDL. When assayed for the ability to transfer lipid to an acceptor particle lacking CE and TG, monkey and hamster CETPs were most effective, although all CETP species were able to promote this one-way movement of neutral lipid. We conclude that CETPs from human, monkey, rabbit, and hamster are not functionally equivalent. Most unique was hamster CETP, which strongly prefers TG as a substrate and promotes the net flow of lipid from VLDL to HDL. << Less

  J. Lipid Res. 55:258-265(2014) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• Transfer of cholesteryl esters and phospholipids as well as net deposition by microsomal triglyceride transfer protein.

  Rava P., Athar H., Johnson C., Hussain M.M.

  Microsomal triglyceride transfer protein (MTP) activity is classically measured using radioactive lipids. We described a simple fluorescence assay to measure its triacylglycerol (TAG) transfer activity. Here, we describe fluorescence-based methods to measure the transfer of phospholipids (PLs) and ... >> More

  Microsomal triglyceride transfer protein (MTP) activity is classically measured using radioactive lipids. We described a simple fluorescence assay to measure its triacylglycerol (TAG) transfer activity. Here, we describe fluorescence-based methods to measure the transfer of phospholipids (PLs) and cholesteryl esters (CEs) by MTP. Both transfer activities increased with time and MTP amounts and were inhibited to different extents by an MTP antagonist, BMS197636. We also describe a method to measure the net deposition of fluorescent lipids in acceptor vesicles. In this procedure, negatively charged donor vesicles are incubated with MTP and acceptor vesicles, and lipids transferred to acceptors are quantified after the removal of donor vesicles and MTP by the addition of DE52. Lipid deposition in acceptor vesicles was dependent on time and MTP. Using these methods, TAG transfer activity was the most robust activity present in purified MTP; CE and PL transfer activities were 60-71% and 5-13% of the TAG transfer activity, respectively. The method to determine lipid transfer is recommended for routine MTP activity measurements for its simplicity. These methods may help identify specific inhibitors for individual lipid transfer activities, in characterizing different domains involved in transfer, and in the isolation of mutants that bind but cannot transfer lipids. << Less

  J. Lipid Res. 46:1779-1785(2005) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.