Publications

• Targeted mutation of plasma phospholipid transfer protein gene markedly reduces high-density lipoprotein levels.

  Jiang X.C., Bruce C., Mar J., Lin M., Ji Y., Francone O.L., Tall A.R.

  It has been proposed that the plasma phospholipid transfer protein (PLTP) facilitates the transfer of phospholipids and cholesterol from triglyceride-rich lipoproteins (TRL) into high-density lipoproteins (HDL). To evaluate the in vivo role of PLTP in lipoprotein metabolism, we used homologous rec ... >> More

  It has been proposed that the plasma phospholipid transfer protein (PLTP) facilitates the transfer of phospholipids and cholesterol from triglyceride-rich lipoproteins (TRL) into high-density lipoproteins (HDL). To evaluate the in vivo role of PLTP in lipoprotein metabolism, we used homologous recombination in embryonic stem cells and produced mice with no PLTP gene expression. Analysis of plasma of F2 homozygous PLTP-/-mice showed complete loss of phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, sphingomyelin, and partial loss of free cholesterol transfer activities. Moreover, the in vivo transfer of [3H]phosphatidylcholine ether from very-low-density proteins (VLDL) to HDL was abolished in PLTP-/-mice. On a chow diet, PLTP-/-mice showed marked decreases in HDL phospholipid (60%), cholesterol (65%), and apo AI (85%), but no significant change in non-HDL lipid or apo B levels, compared with wild-type littermates. On a high-fat diet, HDL levels were similarly decreased, but there was also an increase in VLDL and LDL phospholipids (210%), free cholesterol (60%), and cholesteryl ester (40%) without change in apo B levels, suggesting accumulation of surface components of TRL. Vesicular lipoproteins were shown by negative-stain electron microscopy of the free cholesterol- and phospholipid-enriched IDL/LDL fraction. Thus, PLTP is the major factor facilitating transfer of VLDL phospholipid into HDL. Reduced plasma PLTP activity causes markedly decreased HDL lipid and apoprotein, demonstrating the importance of transfer of surface components of TRL in the maintenance of HDL levels. Vesicular lipoproteins accumulating in PLTP-/-mice on a high-fat diet could influence the development of atherosclerosis. << Less

  J. Clin. Invest. 103:907-914(1999) [PubMed] [EuropePMC]

  This publication is cited by 6 other entries.

• An isoform of the phosphatidylinositol-transfer protein transfers sphingomyelin and is associated with the Golgi system.

  de Vries K.J., Heinrichs A.A., Cunningham E., Brunink F., Westerman J., Somerharju P.J., Cockcroft S., Wirtz K.W., Snoek G.T.

  An isoform of the phosphatidylinositol-transfer protein (PI-TP) was identified in the cytosol fraction of bovine brain. This protein, designated PI-TP beta, has an apparent molecular mass of 36 kDa and an isoelectric point of 5.4. The N-terminal amino acid sequence (21 residues) is 90% similar to ... >> More

  An isoform of the phosphatidylinositol-transfer protein (PI-TP) was identified in the cytosol fraction of bovine brain. This protein, designated PI-TP beta, has an apparent molecular mass of 36 kDa and an isoelectric point of 5.4. The N-terminal amino acid sequence (21 residues) is 90% similar to that of bovine brain PI-TP, henceforth designated PI-TP alpha (molecular mass 35 kDa and pI 5.5). As observed for PI-TP alpha, PI-TP beta has a distinct preference for phosphatidylinositol over phosphatidylcholine. In addition, it expresses a high transfer activity towards sphingomyelin. PI-TP alpha lacks this activity completely. By indirect immunofluorescence we demonstrated that, in Swiss mouse 3T3 fibroblasts, PI-TP beta is preferentially associated with the Golgi system whereas PI-TP alpha is predominantly present in the cytoplasm and the nucleus. In cytosol-depleted HL60 cells, both PI-TP alpha and PI-TP beta were equally effective at reconstituting guanosine 5'-[gamma-thio]triphosphate-mediated phospholipase C beta activity. << Less

  Biochem. J. 310:643-649(1995) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Functional expression of human and mouse plasma phospholipid transfer protein: effect of recombinant and plasma PLTP on HDL subspecies.

  Albers J.J., Wolfbauer G., Cheung M.C., Day J.R., Ching A.F.T., Lok S., Tu A.-Y.

  The molecular cloning of mouse plasma phospholipid transfer protein (PLTP) and the eukaryotic cell expression of complementary DNA for mouse and human PLTP are described. Mouse PLTP was found to share 83% amino acid sequence identity with human PLTP. PLTP was produced in baby hamster kidney cells. ... >> More

  The molecular cloning of mouse plasma phospholipid transfer protein (PLTP) and the eukaryotic cell expression of complementary DNA for mouse and human PLTP are described. Mouse PLTP was found to share 83% amino acid sequence identity with human PLTP. PLTP was produced in baby hamster kidney cells. Conditioned medium from BHK cells expressing PLTP possessed both phospholipid transfer activity and high density lipoprotein (HDL) conversion activity. PLTP mRNA was detected in all 16 human tissues examined by Northern blot analysis with ovary, thymus, and placenta having the highest levels. PLTP mRNA was also examined in eight mouse tissues with the highest PLTP mRNA levels found in the lung, brain, and heart. The effect of purified human plasma-derived PLTP and human recombinant PLTP (rPLTP) on the two human plasma HDL subspecies Lp(A-I) and Lp(A-I/A-II) was evaluated. Plasma PLTP or rPLTP converted the two distinct size subspecies of Lp(A-I) into a larger species, an intermediate species, and a smaller species. Lp(A-I/A-II) particles containing multiple size subspecies were significantly altered by incubation with either plasma or rPLTP with the largest but less prominent subspecies becoming the predominant one, and the smallest subspecies increasing in concentration. Thus, PLTP promoted the conversion of both Lp(A-I) and Lp(A-I/A-II) to populations of larger and smaller particles. Also, both human PLTP and mouse rPLTP were able to convert human or mouse HDL into larger and smaller particles. These observations suggest that PLTP may play a key role in extracellular phospholipid transport and modulation of HDL particles. << Less

  Biochim. Biophys. Acta 1258:27-34(1995) [PubMed] [EuropePMC]

• Sterol carrier protein X is peroxisomal 3-oxoacyl coenzyme A thiolase with intrinsic sterol carrier and lipid transfer activity.

  Seedorf U., Brysch P., Engel T., Schrage K., Assmann G.

  Sterol carrier protein 2 (SCP2; also called nonspecific lipid transfer protein) is a small basic sterol carrier and lipid transfer protein assumed to participate in the intracellular transport of sterols and certain other lipids. Upon cloning and sequencing SCP2-encoding cDNAs, we and others found ... >> More

  Sterol carrier protein 2 (SCP2; also called nonspecific lipid transfer protein) is a small basic sterol carrier and lipid transfer protein assumed to participate in the intracellular transport of sterols and certain other lipids. Upon cloning and sequencing SCP2-encoding cDNAs, we and others found cDNAs containing unexpected in-frame 5'-extensions of up to 1,250 nucleotides upstream of the initiator ATG of the cDNA encoding pre-SCP2. The corresponding transcripts are primarily expressed in the liver and are predicted to encode a previously undescribed fusion protein containing a 143-amino acid C-terminal domain completely identical to pre-SCP2 and a 404-amino acid N-terminal domain with unknown biochemical activity or function (named sterol carrier protein x, SCPx). Here, we show that purified recombinant SCPx cleaves 3-oxoacyl(n)-CoA to yield acetyl-CoA and acyl(n-2)-CoA. Like SCP2, recombinant SCPx also stimulates the microsomal conversion of 7-dehydrocholesterol to cholesterol and transfers phosphatidylcholine and 7-dehydrocholesterol from small unilamellar vesicles to acceptor membranes in vitro. Furthermore, SCPx epitopes are primarily detected within peroxisomes. These findings suggest that SCPx is a previously undescribed peroxisomal 3-ketoacyl-CoA thiolase (EC 2.3.1.16) with intrinsic sterol carrier and lipid transfer activity (suggested name: SCP2/3-oxoacyl-CoA thiolase). << Less

  J. Biol. Chem. 269:21277-21283(1994) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• Molecular and macromolecular specificity of human plasma phospholipid transfer protein.

  Rao R., Albers J.J., Wolfbauer G., Pownall H.J.

  Phospholipid transfer protein (PLTP), also known as lipid transfer protein 2 (LTP-2), mediates a transfer of phospholipids between high-density lipoproteins (HDL). The molecular and macromolecular specificities of recombinant human PLTP were studied using a fluorometric assay based on the excimer ... >> More

  Phospholipid transfer protein (PLTP), also known as lipid transfer protein 2 (LTP-2), mediates a transfer of phospholipids between high-density lipoproteins (HDL). The molecular and macromolecular specificities of recombinant human PLTP were studied using a fluorometric assay based on the excimer fluorescence of pyrenyl lipids. To determine lipoprotein specificity of PLTP, donor very low density lipoproteins (VLDL), low-density lipoproteins (LDL), and HDL were labeled with 1-palmitoyl-2-[10-(1-pyrenyl)decanoyl]phosphatidylcholine (PPyDPC) and incubated with unlabeled acceptor VLDL, LDL, and HDL in every pairwise combination. The highest rate of PPyDPC transfer mediated by PLTP occurred between donor HDL and acceptor HDL. Reassembled HDL (rHDL) consisting of 1-palmitoyl-2-oleoylphosphatidylcholine, apolipoprotein A-I, and pyrene lipids (100:1:4) were used to demonstrate that PLTP transfers diacylglyceride > phosphatidic acid > sphingomyelin > phosphatidylcholine (PC) > phosphatidylglycerol > cerobroside > phosphatidylethanolamine. Thus, PLTP transfers a variety of lipids with two carbon chains and a polar head group. Unsaturation of one PC acyl chain greatly increased transfer rate, whereas increasing chain length and exchanging sn-1/sn-2 position had only small effects. The rate of PPyDPC transfer by PLTP decreases with increasing free cholesterol content in rHDL and with decreasing HDL size. In contrast to spontaneous transfer, PLTP mediates the accumulation of PC in small rHDL particles. PLTP may be important in vivo in the recycling of PC from mature HDL to nascent HDL, the latter of which are the initial acceptors of cholesterol from peripheral tissue for reverse cholesterol transport to the liver. << Less

  Biochemistry 36:3645-3653(1997) [PubMed] [EuropePMC]

  This publication is cited by 5 other entries.

• Genome-wide CRISPR screen reveals CLPTM1L as a lipid scramblase required for efficient glycosylphosphatidylinositol biosynthesis.

  Wang Y., Menon A.K., Maki Y., Liu Y.S., Iwasaki Y., Fujita M., Guerrero P.A., Silva D.V., Seeberger P.H., Murakami Y., Kinoshita T.

  SignificanceScramblases translocate lipids across the lipid bilayer without consumption of ATP, thereby regulating lipid distributions in cellular membranes. Cytosol-to-lumen translocation across the endoplasmic reticulum (ER) membrane is a common process among lipid glycoconjugates involved in po ... >> More

  SignificanceScramblases translocate lipids across the lipid bilayer without consumption of ATP, thereby regulating lipid distributions in cellular membranes. Cytosol-to-lumen translocation across the endoplasmic reticulum (ER) membrane is a common process among lipid glycoconjugates involved in posttranslational protein modifications in eukaryotes. These translocations are thought to be mediated by specific ER-resident scramblases, but the identity of these proteins and the underlying molecular mechanisms have been elusive. Here, we show that CLPTM1L, an integral membrane protein with eight putative transmembrane domains, is the major lipid scramblase involved in efficient glycosylphosphatidylinositol biosynthesis in the ER membrane. Our results validate the long-standing hypothesis that lipid scramblases ensure the efficient translocations of lipid glycoconjugates across the ER membrane for protein glycosylation pathways. << Less

  Proc. Natl. Acad. Sci. U.S.A. 119:e2115083119-e2115083119(2022) [PubMed] [EuropePMC]

  This publication is cited by 6 other entries.

• Over-expression of recombinant human phospholipid scramblase 1 in E. coli and its purification from inclusion bodies.

  Sahu S.K., Gopala Krishna A., Gummadi S.N.

  Human phospholipid scramblase 1 (hPLSCR1) scrambles plasma membrane phospholipids during cell activation, blood coagulation and apoptosis. It was over-expressed in E. coli with a histidine tag and purified from the inclusion bodies (*30 mg/l culture broth) under denaturing conditions using 8 M ure ... >> More

  Human phospholipid scramblase 1 (hPLSCR1) scrambles plasma membrane phospholipids during cell activation, blood coagulation and apoptosis. It was over-expressed in E. coli with a histidine tag and purified from the inclusion bodies (*30 mg/l culture broth) under denaturing conditions using 8 M urea. The denatured hPLSCR1 refolded into its native configuration when urea was removed as shown by a 10-fold increase in its intrinsic fluorescence. Active hPLSCR1 showed scrambling activity in vitro after reconstituting in proteoliposomes. hPLSCR1 showed higher rates of scrambling activity for phosphatidylethanolamine than phosphatidylcholine. Binding studies with the calcium analogue "Stains-all" dye showed a characteristic peak, termed as the J band, at 650 nm. This is the first report on high level expression of hPLSCR1 with histidine tag in E. coli. << Less

  Biotechnol. Lett. 30:2131-2137(2008) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Phosphatidylinositol transfer protein, cytoplasmic 1 (PITPNC1) binds and transfers phosphatidic acid.

  Garner K., Hunt A.N., Koster G., Somerharju P., Groves E., Li M., Raghu P., Holic R., Cockcroft S.

  Phosphatidylinositol transfer proteins (PITPs) are versatile proteins required for signal transduction and membrane traffic. The best characterized mammalian PITPs are the Class I PITPs, PITPα (PITPNA) and PITPβ (PITPNB), which are single domain proteins with a hydrophobic cavity that binds a phos ... >> More

  Phosphatidylinositol transfer proteins (PITPs) are versatile proteins required for signal transduction and membrane traffic. The best characterized mammalian PITPs are the Class I PITPs, PITPα (PITPNA) and PITPβ (PITPNB), which are single domain proteins with a hydrophobic cavity that binds a phosphatidylinositol (PI) or phosphatidylcholine molecule. In this study, we report the lipid binding properties of an uncharacterized soluble PITP, phosphatidylinositol transfer protein, cytoplasmic 1 (PITPNC1) (alternative name, RdgBβ), of the Class II family. We show that the lipid binding properties of this protein are distinct to Class I PITPs because, besides PI, RdgBβ binds and transfers phosphatidic acid (PA) but hardly binds phosphatidylcholine. RdgBβ when purified from Escherichia coli is preloaded with PA and phosphatidylglycerol. When RdgBβ was incubated with permeabilized HL60 cells, phosphatidylglycerol was released, and PA and PI were now incorporated into RdgBβ. After an increase in PA levels following activation of endogenous phospholipase D or after addition of bacterial phospholipase D, binding of PA to RdgBβ was greater at the expense of PI binding. We propose that RdgBβ, when containing PA, regulates an effector protein or can facilitate lipid transfer between membrane compartments. << Less

  J. Biol. Chem. 287:32263-32276(2012) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.