The Experts below are selected from a list of 15945 Experts worldwide ranked by ideXlab platform
Helen H Hobbs - One of the best experts on this subject based on the ideXlab platform.
-
structural role of ABCG5 abcg8 in sterol transport
Biophysical Journal, 2017Co-Authors: Jyh-yeuan Lee, Daniel M. Rosenbaum, Helen H HobbsAbstract:ATP binding cassette (ABC) transporters play critical roles in maintaining sterol homeostasis in eukaryotic organisms, including yeast, plants and mammals. In humans, the heterodimeric ABCG5/ABCG8 (G5G8) mediates the excretion of cholesterol and dietary plant sterols into bile and into the gut lumen. Mutations inactivating either ABCG5 or ABCG8 cause sitosterolemia, a rare autosomal recessive genetic disorder characterized by plant sterol accumulation, hypercholesterolemia, and premature coronary atherosclerosis. ABCG5 and ABCG8 are half ABC transporters;each subunit consists of an N-terminal nucleotide-binding domain (NBD) and a C-terminal transmembrane domain (TMD). The NBDs dimerize to form two catalytically asymmetric nucleotide-binding sites (NBS), one that is catalytically active (NBS2) and the other inactive (NBS1). To understand the structural basis for G5G8-mediated sterol transport we developed a large-scale purification of human G5G8 by exploiting Pichia patoris yeast. We crystallized the transporter in lipid bilayers, solved its structure in a nucleotide-free state at 3.9 A resolution, and generated the first atomic model of an ABC sterol transporter. G5G8 presents a new structural configuration for the TMD of ABC transporters, which is present in a large and functionally diverse ABC2 superfamily. We discover that the TMD and the NBS are coupled through networks of interactions that differ between NBS1 and NBS2, reflecting the catalytic asymmetry of the transporter. A series of conserved polar residues in the TMD form polar networks that we proposed play a role in transmitting signals from the ATPase catalysis in the NBS to sterol transport on the TMD. Molecular dynamic simulation and long-range coevolution analysis revealed an inward-upward TMD movement that predicts a significant conformational change between the TMD subunits. Thus, the G5G8 structure provides a molecular framework that allows us to propose a mechanistic model for ABC transporter-mediated sterol transport and to analyze the disruptive effects of mutations causing sitosterolemia. The structure will serve as a structural template for homology modelling to a wide range of transport system that is regulated by ABCG transporters and by ABC2 superfamily.
-
Structural Role of ABCG5/ABCG8 in Sterol Transport
Biophysical Journal, 2017Co-Authors: Jyh-yeuan Lee, Daniel M. Rosenbaum, Helen H HobbsAbstract:ATP binding cassette (ABC) transporters play critical roles in maintaining sterol homeostasis in eukaryotic organisms, including yeast, plants and mammals. In humans, the heterodimeric ABCG5/ABCG8 (G5G8) mediates the excretion of cholesterol and dietary plant sterols into bile and into the gut lumen. Mutations inactivating either ABCG5 or ABCG8 cause sitosterolemia, a rare autosomal recessive genetic disorder characterized by plant sterol accumulation, hypercholesterolemia, and premature coronary atherosclerosis. ABCG5 and ABCG8 are half ABC transporters;each subunit consists of an N-terminal nucleotide-binding domain (NBD) and a C-terminal transmembrane domain (TMD). The NBDs dimerize to form two catalytically asymmetric nucleotide-binding sites (NBS), one that is catalytically active (NBS2) and the other inactive (NBS1). To understand the structural basis for G5G8-mediated sterol transport we developed a large-scale purification of human G5G8 by exploiting Pichia patoris yeast. We crystallized the transporter in lipid bilayers, solved its structure in a nucleotide-free state at 3.9 A resolution, and generated the first atomic model of an ABC sterol transporter. G5G8 presents a new structural configuration for the TMD of ABC transporters, which is present in a large and functionally diverse ABC2 superfamily. We discover that the TMD and the NBS are coupled through networks of interactions that differ between NBS1 and NBS2, reflecting the catalytic asymmetry of the transporter. A series of conserved polar residues in the TMD form polar networks that we proposed play a role in transmitting signals from the ATPase catalysis in the NBS to sterol transport on the TMD. Molecular dynamic simulation and long-range coevolution analysis revealed an inward-upward TMD movement that predicts a significant conformational change between the TMD subunits. Thus, the G5G8 structure provides a molecular framework that allows us to propose a mechanistic model for ABC transporter-mediated sterol transport and to analyze the disruptive effects of mutations causing sitosterolemia. The structure will serve as a structural template for homology modelling to a wide range of transport system that is regulated by ABCG transporters and by ABC2 superfamily.
-
selective sterol accumulation in ABCG5 abcg8 deficient mice
Journal of Lipid Research, 2004Co-Authors: Klaus Von Bergmann, Dieter Lutjohann, Helen H Hobbs, Jonathan CohenAbstract:The ATP binding cassette (ABC) transporters ABCG5 and ABCG8 limit intestinal absorption and promote biliary secretion of neutral sterols. Mutations in either gene cause sitosterolemia, a rare recessive disease in which plasma and tissue levels of several neutral sterols are in- creased to varying degrees. To determine why patients with sitosterolemia preferentially accumulate noncholesterol ste- rols, levels of cholesterol and the major plant sterols were compared in plasma, liver, bile, and brain of wild-type and ABCG5/ABCG8-deficient ( G5G8 � / � ) mice. The total sterol content of liver and plasma was similar in G5G8 � / � mice and wild-type animals despite an � 30-fold increase in non- cholesterol sterol levels in the knockout animals. The relative enrichment of each sterol in the plasma and liver of G5G8 � / � mice (stigmasterolsitosterolcholestanolbassicas- terolcampesterolcholesterol) reflected its relative en- richment in the bile of wild-type mice. These results indi- cate that 24-alkylated, � 22 , and 5 � -reduced sterols are preferentially secreted into bile and that preferential biliary secretion of noncholesterol sterols by ABCG5 and ABCG8 prevents the accumulation of these sterols in normal ani- mals. The mRNA levels for 13 enzymes in the cholesterol biosynthetic pathway were reduced in the livers of the G5G8 � / � mice, despite a 50% reduction in hepatic choles- terol level. Thus, the accumulation of sterols other than cholesterol is sensed by the cholesterol regulatory machin- ery. —Yu, L., K. von Bergmann, D. Lutjohann, H. H. Hobbs, and J. C. Cohen. Selective sterol accumulation in ABCG5/ ABCG8-deficient mice. J. Lipid Res. 2004. 45: 301-307.
-
Selective sterol accumulation in ABCG5/ABCG8-deficient mice
Journal of lipid research, 2003Co-Authors: Klaus Von Bergmann, Dieter Lutjohann, Helen H Hobbs, Jonathan CohenAbstract:The ATP binding cassette (ABC) transporters ABCG5 and ABCG8 limit intestinal absorption and promote biliary secretion of neutral sterols. Mutations in either gene cause sitosterolemia, a rare recessive disease in which plasma and tissue levels of several neutral sterols are in- creased to varying degrees. To determine why patients with sitosterolemia preferentially accumulate noncholesterol ste- rols, levels of cholesterol and the major plant sterols were compared in plasma, liver, bile, and brain of wild-type and ABCG5/ABCG8-deficient ( G5G8 � / � ) mice. The total sterol content of liver and plasma was similar in G5G8 � / � mice and wild-type animals despite an � 30-fold increase in non- cholesterol sterol levels in the knockout animals. The relative enrichment of each sterol in the plasma and liver of G5G8 � / � mice (stigmasterolsitosterolcholestanolbassicas- terolcampesterolcholesterol) reflected its relative en- richment in the bile of wild-type mice. These results indi- cate that 24-alkylated, � 22 , and 5 � -reduced sterols are preferentially secreted into bile and that preferential biliary secretion of noncholesterol sterols by ABCG5 and ABCG8 prevents the accumulation of these sterols in normal ani- mals. The mRNA levels for 13 enzymes in the cholesterol biosynthetic pathway were reduced in the livers of the G5G8 � / � mice, despite a 50% reduction in hepatic choles- terol level. Thus, the accumulation of sterols other than cholesterol is sensed by the cholesterol regulatory machin- ery. —Yu, L., K. von Bergmann, D. Lutjohann, H. H. Hobbs, and J. C. Cohen. Selective sterol accumulation in ABCG5/ ABCG8-deficient mice. J. Lipid Res. 2004. 45: 301-307.
-
Stimulation of Cholesterol Excretion by the Liver X Receptor Agonist Requires ATP-binding Cassette Transporters G5 and G8
Journal of Biological Chemistry, 2003Co-Authors: Liqing Yu, Jennifer York, Klaus Von Bergmann, Dieter Lutjohann, Jonathan Cohen, Helen H HobbsAbstract:Abstract Liver X receptor (LXR) is a nuclear receptor that plays a crucial role in orchestrating the trafficking of sterols between tissues. Treatment of mice with a potent and specific LXR agonist, T0901317, is associated with increased biliary cholesterol secretion, decreased fractional cholesterol absorption, and increased fecal neutral sterol excretion. Here we show that expression of two target genes of LXRα, the ATP-binding cassette (ABC) transportersABCG5 and Abcg8, is required for both the increase in sterol excretion and the decrease in fractional cholesterol absorption associated with LXR agonist treatment. Mice expressing no ABCG5 and ABCG8 (G5G8 −/− mice) and their littermate controls were treated for 7 days with T0901317. In wild type animals, treatment with the LXR agonist resulted in a 3-fold increase in biliary cholesterol concentrations, a 25% reduction in fractional cholesterol absorption, and a 4-fold elevation in fecal neutral sterol excretion. In contrast, the LXR agonist did not significantly affect biliary cholesterol levels, fractional cholesterol absorption, or neutral fecal sterol excretion in the G5G8 −/−mice. Thus ABCG5 and Abcg8 are required for LXR agonist-associated changes in dietary and biliary sterol trafficking. These results establish a central role for ABCG5 and ABCG8 in promoting cholesterol excretion in vivo.
Albert K. Groen - One of the best experts on this subject based on the ideXlab platform.
-
hepatic ABCG5 g8 overexpression substantially increases biliary cholesterol secretion but does not impact in vivo macrophage to feces rct
Atherosclerosis, 2015Co-Authors: Arne Dikkers, Jan Freark De Boer, Albert K. Groen, Uwe J. F. TietgeAbstract:Abstract Background and aims Biliary cholesterol secretion is important for reverse cholesterol transport (RCT). ABCG5/G8 contribute most cholesterol mass secretion into bile. We investigated the impact of hepatic ABCG5/G8 on cholesterol metabolism and RCT. Methods Biliary and fecal sterol excretion (FSE) as well as RCT were determined using wild-type controls, Abcg8 knockout mice, Abcg8 knockouts with adenovirus-mediated hepatocyte-specific Abcg8 reinstitution and hepatic ABCG5/g8 overexpression in wild-types. Results In Abcg8 knockouts, biliary cholesterol secretion was decreased by 75% (p Conclusions ABCG5/G8 mediate mass biliary cholesterol secretion but not from a RCT-relevant pool. Intervention strategies aiming at increasing hepatic ABCG5/g8 expression for enhancing RCT are not likely to be successful.
-
Hepatic ABCG5/G8 overexpression substantially increases biliary cholesterol secretion but does not impact in vivo macrophage-to-feces RCT.
Atherosclerosis, 2015Co-Authors: Arne Dikkers, Jan Freark De Boer, Albert K. Groen, Uwe J. F. TietgeAbstract:Abstract Background and aims Biliary cholesterol secretion is important for reverse cholesterol transport (RCT). ABCG5/G8 contribute most cholesterol mass secretion into bile. We investigated the impact of hepatic ABCG5/G8 on cholesterol metabolism and RCT. Methods Biliary and fecal sterol excretion (FSE) as well as RCT were determined using wild-type controls, Abcg8 knockout mice, Abcg8 knockouts with adenovirus-mediated hepatocyte-specific Abcg8 reinstitution and hepatic ABCG5/g8 overexpression in wild-types. Results In Abcg8 knockouts, biliary cholesterol secretion was decreased by 75% (p Conclusions ABCG5/G8 mediate mass biliary cholesterol secretion but not from a RCT-relevant pool. Intervention strategies aiming at increasing hepatic ABCG5/g8 expression for enhancing RCT are not likely to be successful.
-
the sterol transporting heterodimer ABCG5 abcg8 requires bile salts to mediate cholesterol efflux
FEBS Letters, 2007Co-Authors: Carlos L J Vrins, Edwin Vink, Kristin E. Vandenberghe, Raoul J. J. M. Frijters, Jurgen Seppen, Albert K. GroenAbstract:The ATP binding cassette transporters ABCG5 and ABCG8 are indispensable for hepatobiliary cholesterol transport. In this study, we investigated the specificity of the heterodimer for cholesterol acceptors. Dog gallbladder epithelial cells were mono- or double-transfected with lentiviral mouse ABCG5 and Abcg8 vectors. Double-transfected cells showed increased efflux to different bile salt (BS) species, while mono-transfected cells did not show enhanced efflux. The efflux was initiated at micellar concentrations and addition of phosphatidylcholine increased efflux. Cholesterol secretion was highly BS dependent, whereas other cholesterol acceptors such as ApoAI, HDL or methyl-β-cyclodextrin did not elicit ABCG5/g8 dependent cholesterol secretion.
-
The sterol transporting heterodimer ABCG5/ABCG8 requires bile salts to mediate cholesterol efflux
FEBS letters, 2007Co-Authors: Carlos L J Vrins, Edwin Vink, Kristin E. Vandenberghe, Raoul J. J. M. Frijters, Jurgen Seppen, Albert K. GroenAbstract:The ATP binding cassette transporters ABCG5 and ABCG8 are indispensable for hepatobiliary cholesterol transport. In this study, we investigated the specificity of the heterodimer for cholesterol acceptors. Dog gallbladder epithelial cells were mono- or double-transfected with lentiviral mouse ABCG5 and Abcg8 vectors. Double-transfected cells showed increased efflux to different bile salt (BS) species, while mono-transfected cells did not show enhanced efflux. The efflux was initiated at micellar concentrations and addition of phosphatidylcholine increased efflux. Cholesterol secretion was highly BS dependent, whereas other cholesterol acceptors such as ApoAI, HDL or methyl-β-cyclodextrin did not elicit ABCG5/g8 dependent cholesterol secretion.
-
the mechanism of ABCG5 abcg8 in biliary cholesterol secretion in mice
Journal of Lipid Research, 2006Co-Authors: Astrid Kosters, Cindy Kunne, Ronald Oude P J Elferink, Shailendra B. Patel, Norbert Looije, Albert K. GroenAbstract:The main player in biliary cholesterol secretion is the heterodimeric transporter complex, ABCG5/ABCG8, the function of which is necessary for the majority of sterols secreted into bile. It is not clear whether the primary step in this process is flopping of cholesterol from the inner to the outer leaflet of the canalicular membrane, with desorption by mixed micelles, or decreasing of the activation energy required for cholesterol desorption from the outer membrane leaflet. In this study, we investigated these mechanisms by infusing Abcg8+/+, Abcg8+/−, and Abcg8−/− mice with hydrophilic and hydrophobic bile salts. In Abcg8−/− mice, this failed to substantially stimulate biliary cholesterol secretion. Infusion of the hydrophobic bile salt taurodeoxycholate also resulted in cholestasis, which was induced in Abcg8−/− mice at a much lower infusion rate compared with Abc8−/− and Abcg8+/− mice, suggesting a reduced cholesterol content in the outer leaflet of the canalicular membrane. Indeed, isolation of canalicular membranes revealed a reduction of 45% in cholesterol content under these conditions in Abcg8−/− mice. Our data support the model that ABCG5/ABCG8 primarily play a role in flopping cholesterol (and sterols) from the inner leaflet to the outer leaflet of the canalicular membrane.—Kosters, A., C. Kunne, N. Looije, S. B. Patel, R. P. J. Oude Elferink, and A. K. Groen. The mechanism of ABCG5/ABCG8 in biliary cholesterol secretion in mice.
Jyh-yeuan Lee - One of the best experts on this subject based on the ideXlab platform.
-
Picky ABCG5/G8 and promiscuous ABCG2 - a tale of fatty diets and drug toxicity.
FEBS letters, 2020Co-Authors: Narakorn Khunweeraphong, James Mitchell‐white, Dániel Szöllősi, Toka O.k. Hussein, Karl Kuchler, Ian D. Kerr, Thomas Stockner, Jyh-yeuan LeeAbstract:Structural data on ABCG5/G8 and ABCG2 reveal a unique molecular architecture for subfamily-G ATP-binding cassette (ABCG) transporters and disclose putative substrate binding sites. ABCG5/G8 and ABCG2 appear to use several unique structural motifs to execute transport, including the triple helical bundles, the membrane-embedded polar relay, the re-entry helices, and a hydrophobic valve. Interestingly, ABCG2 shows extreme substrate promiscuity, whereas ABCG5/G8 transport only sterol molecules. ABCG2 structures suggest a large internal cavity, serving as a binding region for substrates and inhibitors, while mutational and pharmacological analyses support the notion of multiple binding sites. By contrast, ABCG5/G8 shows a collapsed cavity of insufficient size to hold substrates. Indeed, mutational analyses indicate a sterol-binding site at the hydrophobic interface between the transporter and the lipid bilayer. In this review, we highlight key differences and similarities between ABCG2 and ABCG5/G8 structures. We further discuss the relevance of distinct and shared structural features in the context of their physiological functions. Finally, we elaborate on how ABCG2 and ABCG5/G8 could pave the way for studies on other ABCG transporters.
-
picky ABCG5 g8 and promiscuous abcg2 a tale of fatty diets and drug toxicity
FEBS Letters, 2020Co-Authors: Narakorn Khunweeraphong, Dániel Szöllősi, Toka O.k. Hussein, Karl Kuchler, Ian D. Kerr, Thomas Stockner, James Mitchellwhite, Jyh-yeuan LeeAbstract:Structural data on ABCG5/G8 and ABCG2 reveal a unique molecular architecture for subfamily-G ATP-binding cassette (ABCG) transporters and disclose putative substrate binding sites. ABCG5/G8 and ABCG2 appear to use several unique structural motifs to execute transport, including the triple helical bundles, the membrane-embedded polar relay, the re-entry helices, and a hydrophobic valve. Interestingly, ABCG2 shows extreme substrate promiscuity, whereas ABCG5/G8 transport only sterol molecules. ABCG2 structures suggest a large internal cavity, serving as a binding region for substrates and inhibitors, while mutational and pharmacological analyses support the notion of multiple binding sites. By contrast, ABCG5/G8 shows a collapsed cavity of insufficient size to hold substrates. Indeed, mutational analyses indicate a sterol-binding site at the hydrophobic interface between the transporter and the lipid bilayer. In this review, we highlight key differences and similarities between ABCG2 and ABCG5/G8 structures. We further discuss the relevance of distinct and shared structural features in the context of their physiological functions. Finally, we elaborate on how ABCG2 and ABCG5/G8 could pave the way for studies on other ABCG transporters.
-
ABCG5 g8 a structural view to pathophysiology of the hepatobiliary cholesterol secretion
Biochemical Society Transactions, 2019Co-Authors: Aiman A. Zein, Gregory A Graf, Toka O.k. Hussein, Rupinder Kaur, Jyh-yeuan LeeAbstract:The ABCG5/G8 heterodimer is the primary neutral sterol transporter in hepatobiliary and transintestinal cholesterol excretion. Inactivating mutations on either the ABCG5 or ABCG8 subunit cause Sitosterolemia, a rare genetic disorder. In 2016, a crystal structure of human ABCG5/G8 in an apo state showed the first structural information on ATP-binding cassette (ABC) sterol transporters and revealed several structural features that were observed for the first time. Over the past decade, several missense variants of ABCG5/G8 have been associated with non-Sitosterolemia lipid phenotypes. In this review, we summarize recent pathophysiological and structural findings of ABCG5/G8, interpret the structure-function relationship in disease-causing variants and describe the available evidence that allows us to build a mechanistic view of ABCG5/G8-mediated sterol transport.
-
ABCG5/G8: a structural view to pathophysiology of the hepatobiliary cholesterol secretion.
Biochemical Society transactions, 2019Co-Authors: Aiman A. Zein, Gregory A Graf, Toka O.k. Hussein, Rupinder Kaur, Jyh-yeuan LeeAbstract:The ABCG5/G8 heterodimer is the primary neutral sterol transporter in hepatobiliary and transintestinal cholesterol excretion. Inactivating mutations on either the ABCG5 or ABCG8 subunit cause Sitosterolemia, a rare genetic disorder. In 2016, a crystal structure of human ABCG5/G8 in an apo state showed the first structural information on ATP-binding cassette (ABC) sterol transporters and revealed several structural features that were observed for the first time. Over the past decade, several missense variants of ABCG5/G8 have been associated with non-Sitosterolemia lipid phenotypes. In this review, we summarize recent pathophysiological and structural findings of ABCG5/G8, interpret the structure-function relationship in disease-causing variants and describe the available evidence that allows us to build a mechanistic view of ABCG5/G8-mediated sterol transport.
-
structural role of ABCG5 abcg8 in sterol transport
Biophysical Journal, 2017Co-Authors: Jyh-yeuan Lee, Daniel M. Rosenbaum, Helen H HobbsAbstract:ATP binding cassette (ABC) transporters play critical roles in maintaining sterol homeostasis in eukaryotic organisms, including yeast, plants and mammals. In humans, the heterodimeric ABCG5/ABCG8 (G5G8) mediates the excretion of cholesterol and dietary plant sterols into bile and into the gut lumen. Mutations inactivating either ABCG5 or ABCG8 cause sitosterolemia, a rare autosomal recessive genetic disorder characterized by plant sterol accumulation, hypercholesterolemia, and premature coronary atherosclerosis. ABCG5 and ABCG8 are half ABC transporters;each subunit consists of an N-terminal nucleotide-binding domain (NBD) and a C-terminal transmembrane domain (TMD). The NBDs dimerize to form two catalytically asymmetric nucleotide-binding sites (NBS), one that is catalytically active (NBS2) and the other inactive (NBS1). To understand the structural basis for G5G8-mediated sterol transport we developed a large-scale purification of human G5G8 by exploiting Pichia patoris yeast. We crystallized the transporter in lipid bilayers, solved its structure in a nucleotide-free state at 3.9 A resolution, and generated the first atomic model of an ABC sterol transporter. G5G8 presents a new structural configuration for the TMD of ABC transporters, which is present in a large and functionally diverse ABC2 superfamily. We discover that the TMD and the NBS are coupled through networks of interactions that differ between NBS1 and NBS2, reflecting the catalytic asymmetry of the transporter. A series of conserved polar residues in the TMD form polar networks that we proposed play a role in transmitting signals from the ATPase catalysis in the NBS to sterol transport on the TMD. Molecular dynamic simulation and long-range coevolution analysis revealed an inward-upward TMD movement that predicts a significant conformational change between the TMD subunits. Thus, the G5G8 structure provides a molecular framework that allows us to propose a mechanistic model for ABC transporter-mediated sterol transport and to analyze the disruptive effects of mutations causing sitosterolemia. The structure will serve as a structural template for homology modelling to a wide range of transport system that is regulated by ABCG transporters and by ABC2 superfamily.
Shailendra B. Patel - One of the best experts on this subject based on the ideXlab platform.
-
Liver-specific induction of ABCG5 and Abcg8 stimulates reverse cholesterol transport in response to ezetimibe treatment
Metabolism: clinical and experimental, 2014Co-Authors: Jessica B Altemus, Shailendra B. Patel, Ephraim SehayekAbstract:Abstract Objective Previous studies have shown ezetimibe treatment results in a 2–6-fold increase in reverse cholesterol transport (RCT). However, recent sterol balance studies question the role of biliary sterol secretion in RCT, and challenge the hypothesis that ezetimibe increases RCT through decreased absorption of biliary cholesterol in the intestine. We set out to determine whether ezetimibe may increase RCT by mechanisms that are independent of its well-established inhibition of intestinal cholesterol absorption. Methods C57BL/6J, Npc1l1 -KO, and/or Abcg8 -KO mice were fed a chow diet with or without ezetimibe and fecal [ 14 C]-neutral and [ 14 C]-acidic sterols were measured to examine macrophage-to-feces RCT. We measured the expression of RCT related genes in the liver and jejunum in these mice. To confirm our significant gene expression findings, we utilized primary human hepatocytes cultured with or without a glucuronated metabolite of ezetimibe. Results Our studies revealed that treatment with ezetimibe was associated with increased expression of hepatic ABCG5 and Abcg8 . Ezetimibe did not directly affect expression in the liver, but this expression was due to the inhibition of intestinal cholesterol absorption. This conclusion was supported by the absence of an ABCG5/ABCG8 expression response to treatment with an ezetimibe metabolite in primary human hepatocytes. Finally, we found that the ezetimibe-dependent stimulation of RCT was attenuated in the absence of Abcg8 . Conclusions Our study is the first to demonstrate ezetimibe treatment cooperatively stimulated macrophage-to-feces RCT by indirectly increasing liver ABCG5/Abcg8 expression in addition to its known suppression of intestinal cholesterol absorption.
-
the mechanism of ABCG5 abcg8 in biliary cholesterol secretion in mice
Journal of Lipid Research, 2006Co-Authors: Astrid Kosters, Cindy Kunne, Ronald Oude P J Elferink, Shailendra B. Patel, Norbert Looije, Albert K. GroenAbstract:The main player in biliary cholesterol secretion is the heterodimeric transporter complex, ABCG5/ABCG8, the function of which is necessary for the majority of sterols secreted into bile. It is not clear whether the primary step in this process is flopping of cholesterol from the inner to the outer leaflet of the canalicular membrane, with desorption by mixed micelles, or decreasing of the activation energy required for cholesterol desorption from the outer membrane leaflet. In this study, we investigated these mechanisms by infusing Abcg8+/+, Abcg8+/−, and Abcg8−/− mice with hydrophilic and hydrophobic bile salts. In Abcg8−/− mice, this failed to substantially stimulate biliary cholesterol secretion. Infusion of the hydrophobic bile salt taurodeoxycholate also resulted in cholestasis, which was induced in Abcg8−/− mice at a much lower infusion rate compared with Abc8−/− and Abcg8+/− mice, suggesting a reduced cholesterol content in the outer leaflet of the canalicular membrane. Indeed, isolation of canalicular membranes revealed a reduction of 45% in cholesterol content under these conditions in Abcg8−/− mice. Our data support the model that ABCG5/ABCG8 primarily play a role in flopping cholesterol (and sterols) from the inner leaflet to the outer leaflet of the canalicular membrane.—Kosters, A., C. Kunne, N. Looije, S. B. Patel, R. P. J. Oude Elferink, and A. K. Groen. The mechanism of ABCG5/ABCG8 in biliary cholesterol secretion in mice.
-
The mechanism of ABCG5/ABCG8 in biliary cholesterol secretion in mice
Journal of lipid research, 2006Co-Authors: Astrid Kosters, Cindy Kunne, Ronald Oude P J Elferink, Shailendra B. Patel, Norbert Looije, Albert K. GroenAbstract:The main player in biliary cholesterol secretion is the heterodimeric transporter complex, ABCG5/ABCG8, the function of which is necessary for the majority of sterols secreted into bile. It is not clear whether the primary step in this process is flopping of cholesterol from the inner to the outer leaflet of the canalicular membrane, with desorption by mixed micelles, or decreasing of the activation energy required for cholesterol desorption from the outer membrane leaflet. In this study, we investigated these mechanisms by infusing Abcg8+/+, Abcg8+/−, and Abcg8−/− mice with hydrophilic and hydrophobic bile salts. In Abcg8−/− mice, this failed to substantially stimulate biliary cholesterol secretion. Infusion of the hydrophobic bile salt taurodeoxycholate also resulted in cholestasis, which was induced in Abcg8−/− mice at a much lower infusion rate compared with Abc8−/− and Abcg8+/− mice, suggesting a reduced cholesterol content in the outer leaflet of the canalicular membrane. Indeed, isolation of canalicular membranes revealed a reduction of 45% in cholesterol content under these conditions in Abcg8−/− mice. Our data support the model that ABCG5/ABCG8 primarily play a role in flopping cholesterol (and sterols) from the inner leaflet to the outer leaflet of the canalicular membrane.—Kosters, A., C. Kunne, N. Looije, S. B. Patel, R. P. J. Oude Elferink, and A. K. Groen. The mechanism of ABCG5/ABCG8 in biliary cholesterol secretion in mice.
-
molecular cloning genomic organization genetic variations and characterization of murine sterolin genes ABCG5 and abcg8
Journal of Lipid Research, 2002Co-Authors: Kangmo Lu, Hongwei Yu, Yuehua Zhou, Shelley A Sandell, Gerald Salen, Shailendra B. PatelAbstract:Mammalian physiological processes can distinguish between dietary cholesterol and non-cholesterol, retaining very little of the non-cholesterol in their bodies. We have recently identified two genes, ABCG5 and ABCG8, encoding sterolin-1 and -2 respectively, mutations of which cause the human disease sitosterolemia. We report here the mouse cDNAs and genomic organization of ABCG5 and Abcg8. Both genes are arranged in an unusual head-to-head configuration, and only 140 bases separate their two respective start-transcription sites. A single TATA motif was identified, with no canonical CCAT box present between the two genes. The genes are located on mouse chromosome 17 and this complex spans no more than 40 kb. Expression of both genes is confined to the liver and intestine. For both genes, two different sizes of transcripts were identified which differ in the lengths of their 3′ UTRs. Additionally, alternatively spliced forms for Abcg8 were identified, resulting from a CAG repeat at the intron 1 splice-acceptor site, causing a deletion of a glutamine. We screened 20 different mouse strains for polymorphic variants. Although a large number of polymorphic variants were identified, strains reported to show significant differences in cholesterol absorption rates did not show significant genomic variations in ABCG5 or Abcg8.—Lu, K., M-H. Lee, H. Yu, Y. Zhou, S. A. Sandell, G. Salen, and S. B. Patel. Molecular cloning, genomic organization, genetic variations, and characterization of murine sterolin genes ABCG5 and Abcg8.
-
Molecular cloning, genomic organization, genetic variations, and characterization of murine sterolin genes ABCG5 and Abcg8
Journal of lipid research, 2002Co-Authors: Mi Hye Lee, Shelley A Sandell, Yuehua Zhou, Gerald Salen, Shailendra B. PatelAbstract:Mammalian physiological processes can distinguish between dietary cholesterol and non-cholesterol, retaining very little of the non-cholesterol in their bodies. We have recently identified two genes, ABCG5 and ABCG8, encoding sterolin-1 and -2 respectively, mutations of which cause the human disease sitosterolemia. We report here the mouse cDNAs and genomic organization of ABCG5 and Abcg8. Both genes are arranged in an unusual head-to-head configuration, and only 140 bases separate their two respective start-transcription sites. A single TATA motif was identified, with no canonical CCAT box present between the two genes. The genes are located on mouse chromosome 17 and this complex spans no more than 40 kb. Expression of both genes is confined to the liver and intestine. For both genes, two different sizes of transcripts were identified which differ in the lengths of their 3' UTRs. Additionally, alternatively spliced forms for Abcg8 were identified, resulting from a CAG repeat at the intron 1 splice-acceptor site, causing a deletion of a glutamine. We screened 20 different mouse strains for polymorphic variants. Although a large number of polymorphic variants were identified, strains reported to show significant differences in cholesterol absorption rates did not show significant genomic variations in ABCG5 or Abcg8.
Carlos L J Vrins - One of the best experts on this subject based on the ideXlab platform.
-
ABCG5 8 independent biliary cholesterol excretion in atp8b1 deficient mice
Gastroenterology, 2008Co-Authors: A K Groen, Laura N Bull, Geartsje Jongsma, Michele Petruzzelli, Carlos L J Vrins, Cindy Kunne, Karin Van Den Oever, Coen C. Paulusma, Ronald Oude P J ElferinkAbstract:Backgrounds & Aims: ATP8B1 is a phosphatidylserine flippase in the canalicular membrane; patients with mutations in ATP8B1 develop severe chronic (PFIC1) or periodic (BRIC1) cholestatic liver disease. We have observed that Atp8b1 deficiency leads to enhanced biliary cholesterol excretion. It has been established that biliary cholesterol excretion depends on transport by the heterodimer ABCG5/Abcg8. We hypothesized that the increased cholesterol output was due to enhanced extraction from the altered canalicular membrane rather than to higher ABCG5/Abcg8 activity. We therefore studied the relation between ABCG5/Abcg8 expression and biliary cholesterol excretion in mice lacking Atp8b1, Abcg8, or both (GF mice). Methods: Bile formation was studied in LXR agonist-fed wild-type mice as well as mice lacking Atp8b1 or Abcg8, or in GF mice upon infusion of taurocholate. Bile samples were analyzed for cholesterol, bile salt, phospholipids, and ectoenzyme content. Results: LXR agonist increased ABCG5/8 expression, and this was accompanied by increased biliary cholesterol output in both wild-type and Atp8b1G308V/G308V mice. However, Atp8b1G308V/G308V mice maintained higher cholesterol output. Although in Abcg8−/− mice biliary cholesterol output was severely reduced, GF mice displayed high biliary cholesterol output, which was comparable with wild-type mice. Bile of both Atp8b1G308V/G308V and GF mice displayed elevated levels of phosphatidylserine and sphingomyelin, indicating membrane stress. Conclusions: Our data demonstrate that the increased biliary cholesterol excretion in Atp8b1-deficient mice is independent of ABCG5/8 activity. This implicates that Atp8b1 deficiency leads to a decrease in the detergent resistance and subsequent nonspecific extraction of cholesterol from the canalicular membrane by bile salts.
-
ABCG5/8 Independent Biliary Cholesterol Excretion in Atp8b1-Deficient Mice
Gastroenterology, 2008Co-Authors: A K Groen, Laura N Bull, Geartsje Jongsma, Michele Petruzzelli, Carlos L J Vrins, Cindy Kunne, Karin Van Den Oever, Coen C. Paulusma, Ronald Oude P J ElferinkAbstract:Backgrounds & Aims: ATP8B1 is a phosphatidylserine flippase in the canalicular membrane; patients with mutations in ATP8B1 develop severe chronic (PFIC1) or periodic (BRIC1) cholestatic liver disease. We have observed that Atp8b1 deficiency leads to enhanced biliary cholesterol excretion. It has been established that biliary cholesterol excretion depends on transport by the heterodimer ABCG5/Abcg8. We hypothesized that the increased cholesterol output was due to enhanced extraction from the altered canalicular membrane rather than to higher ABCG5/Abcg8 activity. We therefore studied the relation between ABCG5/Abcg8 expression and biliary cholesterol excretion in mice lacking Atp8b1, Abcg8, or both (GF mice). Methods: Bile formation was studied in LXR agonist-fed wild-type mice as well as mice lacking Atp8b1 or Abcg8, or in GF mice upon infusion of taurocholate. Bile samples were analyzed for cholesterol, bile salt, phospholipids, and ectoenzyme content. Results: LXR agonist increased ABCG5/8 expression, and this was accompanied by increased biliary cholesterol output in both wild-type and Atp8b1G308V/G308V mice. However, Atp8b1G308V/G308V mice maintained higher cholesterol output. Although in Abcg8−/− mice biliary cholesterol output was severely reduced, GF mice displayed high biliary cholesterol output, which was comparable with wild-type mice. Bile of both Atp8b1G308V/G308V and GF mice displayed elevated levels of phosphatidylserine and sphingomyelin, indicating membrane stress. Conclusions: Our data demonstrate that the increased biliary cholesterol excretion in Atp8b1-deficient mice is independent of ABCG5/8 activity. This implicates that Atp8b1 deficiency leads to a decrease in the detergent resistance and subsequent nonspecific extraction of cholesterol from the canalicular membrane by bile salts.
-
the sterol transporting heterodimer ABCG5 abcg8 requires bile salts to mediate cholesterol efflux
FEBS Letters, 2007Co-Authors: Carlos L J Vrins, Edwin Vink, Kristin E. Vandenberghe, Raoul J. J. M. Frijters, Jurgen Seppen, Albert K. GroenAbstract:The ATP binding cassette transporters ABCG5 and ABCG8 are indispensable for hepatobiliary cholesterol transport. In this study, we investigated the specificity of the heterodimer for cholesterol acceptors. Dog gallbladder epithelial cells were mono- or double-transfected with lentiviral mouse ABCG5 and Abcg8 vectors. Double-transfected cells showed increased efflux to different bile salt (BS) species, while mono-transfected cells did not show enhanced efflux. The efflux was initiated at micellar concentrations and addition of phosphatidylcholine increased efflux. Cholesterol secretion was highly BS dependent, whereas other cholesterol acceptors such as ApoAI, HDL or methyl-β-cyclodextrin did not elicit ABCG5/g8 dependent cholesterol secretion.
-
The sterol transporting heterodimer ABCG5/ABCG8 requires bile salts to mediate cholesterol efflux
FEBS letters, 2007Co-Authors: Carlos L J Vrins, Edwin Vink, Kristin E. Vandenberghe, Raoul J. J. M. Frijters, Jurgen Seppen, Albert K. GroenAbstract:The ATP binding cassette transporters ABCG5 and ABCG8 are indispensable for hepatobiliary cholesterol transport. In this study, we investigated the specificity of the heterodimer for cholesterol acceptors. Dog gallbladder epithelial cells were mono- or double-transfected with lentiviral mouse ABCG5 and Abcg8 vectors. Double-transfected cells showed increased efflux to different bile salt (BS) species, while mono-transfected cells did not show enhanced efflux. The efflux was initiated at micellar concentrations and addition of phosphatidylcholine increased efflux. Cholesterol secretion was highly BS dependent, whereas other cholesterol acceptors such as ApoAI, HDL or methyl-β-cyclodextrin did not elicit ABCG5/g8 dependent cholesterol secretion.
