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Gerd Schmitz - One of the best experts on this subject based on the ideXlab platform.
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ABCA3 protects alveolar epithelial cells against free cholesterol induced cell death
Biochimica et Biophysica Acta, 2015Co-Authors: Ralf Zarbock, Gerd Schmitz, Gerhard Liebisch, Eva Kaltenborn, Sabrina Frixel, Thomas Wittmann, Matthias GrieseAbstract:Abstract Diffuse parenchymal lung diseases (DPLDs) are characterized by chronic inflammation and fibrotic remodeling of the interstitial tissue. A small fraction of DPLD cases can be genetically defined by mutations in certain genes, with ABCA3 being the gene most commonly affected. However, the pathomechanisms underlying ABCA3-induced DPLD are far from clear. To investigate whether ABCA3 plays a role in cellular cholesterol homeostasis, phospholipids, free cholesterol, and cholesteryl esters were quantified in cells stably expressing ABCA3 using mass spectrometry. Cellular free cholesterol and lipid droplets were visualized by filipin or oil red staining, respectively. Expression of SREBP regulated genes was measured using qPCR. Cell viability was assessed using the XTT assay. We found that wild type ABCA3 reduces cellular free cholesterol levels, induces the SREBP pathway, and renders cells more resistant to loading with exogenous cholesterol. Moreover, ABCA3 mutations found in patients with DPLD interfere with this protective effect of ABCA3, resulting in free cholesterol induced cell death. We conclude that ABCA3 plays a previously unrecognized role in the regulation of cellular cholesterol levels. Accumulation of free cholesterol as a result of a loss of ABCA3 export function represents a novel pathomechanism in ABCA3-induced DPLD.
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Characterization of the ATP-binding cassette transporter gene expression profile in Y79: a retinoblastoma cell line
Molecular and Cellular Biochemistry, 2009Co-Authors: Doris Hendig, Ralf Zarbock, Thomas Langmann, Knut Kleesiek, Gerd Schmitz, Christian GottingAbstract:Chemotherapy failure was reported in treatment of retinoblastoma suggesting a role for ATP-binding cassette (ABC) proteins. Little is known about the expression pattern of ABC proteins in this cancer type. We investigated the gene expression profile of 47 ABC proteins in the human retinoblastoma cell line Y79 by TaqMan low-density array. Analysis revealed 31 ABC transporter genes expressed in this tumor cell line. Y79 cells demonstrate high gene expression of ABCA7 , ABCA12 , ABCB7 , ABCB10 , ABCC1 , ABCC4 , ABCD3 , ABCE1 , ABCF1 , ABCF2 , and ABCF3 (more than twofold compared to pooled RNA from different tissues). Moreover, we show that Y79 cells exhibit an active calcein efflux pointing to multidrug resistance protein (MRP)-like transporter activity. In summary, we present for the first time an ABC transporter gene expression profile in cells derived from retinoblastoma. Most of the highly expressed ABC transporter genes are typical markers of cancer cells and might exhibit potential targets for medical treatment of retinoblastoma.
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mapping atp binding cassette transporter gene expression profiles in melanocytes and melanoma cells
Melanoma Research, 2007Co-Authors: Susanne Heimerl, Thomas Langmann, Anja K Bosserhoff, Josef Ecker, Gerd SchmitzAbstract:ATP-binding cassette (ABC) transporters regulate the transport of a variety of physiologic substrates. Moreover, several human ABC proteins are responsible for drug exclusion in compound-treated tumor cells, providing cellular mechanisms for the development of multidrug resistance and, therefore, playing an important role in malignant transformation. As only limited information exists on the role of ABC transporters in melanoma, the aim of the study was to generate a complete expression profile of ABC transporters in this tumor entity. Using a TaqMan low-density array for 47 human ABC transporters, mRNA expression analysis was performed from normal human epidermal melanocytes (NHEM P2 and NHEM P3), nine different cell lines originating from primary melanoma (Mel Ei, Mel Juso, Mel Ho and Mel Wei), and metastases of malignant melanoma (Mel Im, Mel Ju, SK Mel 28, HTZ 19 and HMB2). Cell line-specific expression levels were compared with gene expression in pooled RNA from a variety of other human tissues. High expression levels were detected in pooled tissue RNA as well as in cells of melanocytic origin for ABCA5, ABCB2, ABCB6, ABCD3, ABCD4, ABCF1, ABCF2 and ABCF3, whereas ABCB5 revealed a melanocyte-specific high transcript level. In relation to normal melanocytes, ABCB3, ABCB6, ABCC2, ABCC4, ABCE1 and ABCF2 were significantly increased in melanoma cell lines, whereas ABCA7, ABCA12, ABCB2, ABCB4, ABCB5 and ABCD1 showed lower expression levels. In summary, we present here for the first time an ABC-transporter mRNA expression profile in melanoma in comparison to normal melanocytes. The differentially regulated ABC transporters detected by our approach may be candidate genes involved in melanoma tumorigenesis, progression and therapy resistance and could therefore be of great importance to identify novel options for melanoma therapy.
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Ultrastructural and molecular analysis in fatal neonatal interstitial pneumonia caused by a novel ABCA3 mutation
Modern Pathology, 2007Co-Authors: Elisabeth Bruder, Gerd Schmitz, Charalampos Aslanidis, Jörg Hofmeister, Jürg Hammer, Lukas Bubendorf, Alex Rufle, Christoph BührerAbstract:Pulmonary surfactant is essential to maintain alveolar patency, and invariably fatal neonatal lung disease has been recognized to involve mutations in the genes encoding surfactant protein-B or ATP-binding cassette transporter family member ABCA3. The lipid transporter ABCA3 targets surfactant phospholipids to lamellar bodies that are lysosomal-derived organelles of alveolar type II cells. ABCA3 −/− mice have grossly reduced surfactant phosphatidyl glycerol levels and die of respiratory failure soon after birth. We studied lung biopsy samples of two siblings with a novel homozygous ABCA3 mutation at nucleotide position 578 (c.578C>G), leading to a Pro193Arg amino-acid exchange, who died at 55 and 105 days of age. Light microscopy revealed thickened alveolar septa with abundant myxoid interstitial matrix, marked hyperplasia of type II pneumocytes, desquamation of alveolar macrophages and focal alveolar proteinosis. Surfactant protein-B was detected by immunohistochemistry after antigen retrieval. Transmission electron microscopy showed rare cytoplasmic inclusions with concentric membranes and eccentrically placed electron-dense aggregates. These ‘fried-egg’-appearing lamellar bodies differed both from normal lamellar bodies and the larger, poorly formed composite bodies with multiple vesicular inclusions observed in surfactant protein-B deficiency. In conclusion, our findings underscore that the implications of interstitial lung disease in infant lungs differ from those in adults. In infants with a desquamative interstitial pneumonitis pattern, surfactant or ABCA3 mutations should be evaluated. Importantly, these findings support the notion that electron microscopy is useful in distinguishing between surfactant protein-B and ABCA3 deficiency, and has an important role in evaluating biopsies or autopsies of term infants with unexplained severe respiratory failure and interstitial lung disease.
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complete coding sequence promoter region and genomic structure of the human abca2 gene and evidence for sterol dependent regulation in macrophages
Biochemical and Biophysical Research Communications, 2001Co-Authors: Wolfgang E Kaminski, Armin Piehler, Kerstin Pullmann, Mustafa Porschozcurumez, Chinh Quoc Duong, Guido Maa Bared, Christa Buchler, Gerd SchmitzAbstract:Members of the human ABC transporter A subfamily have gained considerable attention based on the recent findings that ABCA1 and ABCR (ABCA4) cause familial HDL-deficiency syndromes and distinct forms of hereditary retinopathies, respectively. Here we report the complete cDNA and the genomic organization of ABCA2, another member of the human ABC A transporter subfamily. The ABCA2 coding region is 7.3 kb in size and codes for a 2436 amino acid polypeptide that bears the typical features of a full-size ABC transporter. Among the known members of the ABC A subfamily ABCA2 shares highest homology with the cholesterol-responsive transporters ABCA1 (50%) and the recently cloned ABCA7 (44%). The ABCA2 gene comprises 48 exons which are localized within a genomic region of only 21 kb. Analysis of the putative ABCA2 promoter sequence revealed potential binding sites for transcription factors that are involved in the differentiation of myeloid and neural cells. Gene expression analysis in human macrophages showed that ABCA2 mRNA is induced during cholesterol import indicating that ABCA2 is a cholesterol-responsive gene. Our results suggest a potential role for ABCA2 in macrophage lipid metabolism and neural development.
Robert S Molday - One of the best experts on this subject based on the ideXlab platform.
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differential phospholipid substrates and directional transport by atp binding cassette proteins abca1 abca7 and abca4 and disease causing mutants
Journal of Biological Chemistry, 2013Co-Authors: Faraz Quazi, Robert S MoldayAbstract:Abstract ABCA1, ABCA7, and ABCA4 are members of the ABCA subfamily of ATP-binding cassette transporters which share extensive sequence and structural similarity. Mutations in ABCA1 cause Tangier disease characterized by defective cholesterol homeostasis and high-density lipoprotein (HDL) deficiency. Mutations in ABCA4 are responsible for Stargardt disease, a degenerative disorder associated with severe loss in central vision. Although cell-based studies have implicated ABCA proteins in lipid transport, the substrates and direction of transport have not been firmly established. We have purified and reconstituted ABCA1, ABCA7 and ABCA4 into liposomes for fluorescent-lipid transport studies. ABCA1 actively exported or flipped phosphatidylcholine (PC), phosphatidylserine (PS), and sphingomyelin (SM) from the cytoplasmic to the exocytoplasmic leaflet of membranes, whereas ABCA7 preferentially exported PS. In contrast ABCA4 transported phosphatidylethanolamine (PE) in the reverse direction. The same phospholipids stimulated the ATPase activity of these ABCA transporters. The transport activity and ATPase activity of ABCA1 and ABCA4 was reduced by 25% in the presence of 20% cholesterol. Nine ABCA1 Tangier mutants and corresponding ABCA4 Stargardt mutants showed significantly reduced phospholipid transport activity and subcellular mislocalization. These studies provide the first direct evidence for ABCA1 and ABCA7 functioning as phospholipid transporters and suggest that this activity is an essential step in the loading of ApoA-1 with phospholipids for HDL formation.
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differential phospholipid substrates and directional transport by atp binding cassette proteins abca1 abca7 and abca4 and disease causing mutants
Journal of Biological Chemistry, 2013Co-Authors: Faraz Quazi, Robert S MoldayAbstract:ABCA1, ABCA7, and ABCA4 are members of the ABCA subfamily of ATP-binding cassette transporters that share extensive sequence and structural similarity. Mutations in ABCA1 cause Tangier disease characterized by defective cholesterol homeostasis and high density lipoprotein (HDL) deficiency. Mutations in ABCA4 are responsible for Stargardt disease, a degenerative disorder associated with severe loss in central vision. Although cell-based studies have implicated ABCA proteins in lipid transport, the substrates and direction of transport have not been firmly established. We have purified and reconstituted ABCA1, ABCA7, and ABCA4 into liposomes for fluorescent-lipid transport studies. ABCA1 actively exported or flipped phosphatidylcholine, phosphatidylserine, and sphingomyelin from the cytoplasmic to the exocytoplasmic leaflet of membranes, whereas ABCA7 preferentially exported phosphatidylserine. In contrast, ABCA4 transported phosphatidylethanolamine in the reverse direction. The same phospholipids stimulated the ATPase activity of these ABCA transporters. The transport and ATPase activities of ABCA1 and ABCA4 were reduced by 25% in the presence of 20% cholesterol. Nine ABCA1 Tangier mutants and the corresponding ABCA4 Stargardt mutants showed significantly reduced phospholipid transport activity and subcellular mislocalization. These studies provide the first direct evidence for ABCA1 and ABCA7 functioning as phospholipid transporters and suggest that this activity is an essential step in the loading of apoA-1 with phospholipids for HDL formation.
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molecular organization and atp induced conformational changes of abca4 the photoreceptor specific abc transporter
Structure, 2013Co-Authors: Yaroslav Tsybovsky, Robert S Molday, Tivadar Orban, Derek J TaylorAbstract:ATP-binding cassette (ABC) transporters use ATP to translocate various substrates across cellular membranes. Several members of subfamily A of mammalian ABC transporters are associated with severe health disorders, but their unusual complexity and large size have so far precluded structural characterization. ABCA4 is localized to the discs of vertebrate photoreceptor outer segments. This protein transports N-retinylidene-phosphatidylethanolamine to the outer side of disc membranes to prevent formation of toxic compounds causing macular degeneration. An 18 A-resolution structure of ABCA4 isolated from bovine rod outer segments was determined using electron microscopy and single-particle reconstruction. Significant conformational changes in the cytoplasmic and transmembrane regions were observed upon binding of a nonhydrolyzable ATP analog and accompanied by altered hydrogen/deuterium exchange in the Walker A motif of one of the nucleotide-binding domains. These findings provide an initial view of the molecular organization and functional rearrangements for any member of the ABCA subfamily of ABC transporters.
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Lipid transport by mammalian ABC proteins.
Essays in biochemistry, 2011Co-Authors: Faraz Quazi, Robert S MoldayAbstract:ABC (ATP-binding cassette) proteins actively transport a wide variety of substrates, including peptides, amino acids, sugars, metals, drugs, vitamins and lipids, across extracellular and intracellular membranes. Of the 49 hum an ABC proteins, a significant number are known to mediate the extrusion of lipids from membranes or the flipping of membrane lipids across the bilayer to generate and maintain membrane lipid asymmetry. Typical lipid substrates include phospholipids, sterols, sphingolipids, bile acids and related lipid conjugates. Members of the ABCA subfamily of ABC transporters and other ABC proteins such as ABCB4, ABCG1 and ABCG5/8 implicated in lipid transport play important roles in diverse biological processes such as cell signalling, membrane lipid asymmetry, removal of potentially toxic compounds and metabolites, and apoptosis. The importance of these ABC lipid transporters in cell physiology is evident from the finding that mutations in the genes encoding many of these proteins are responsible for severe inherited diseases. For example, mutations in ABCA1 cause Tangier disease associated with defective efflux of cholesterol and phosphatidylcholine from the plasma membrane to the lipid acceptor protein apoA1 (apolipoprotein AI), mutations in ABCA3 cause neonatal surfactant deficiency associated with a loss in secretion of the lipid pulmonary surfactants from lungs of newborns, mutations in ABCA4 cause Stargardt macular degeneration, a retinal degenerative disease linked to the reduced clearance of retinoid compounds from photoreceptor cells, mutations in ABCA12 cause harlequin and lamellar ichthyosis, skin diseases associated with defective lipid trafficking in keratinocytes, and mutations in ABCB4 and ABCG5/ABCG8 are responsible for progressive intrafamilial hepatic disease and sitosterolaemia associated with defective phospholipid and sterol transport respectively. This chapter highlights the involvement of various mammalian ABC transporters in lipid transport in the context of their role in cell signalling, cellular homoeostasis, apoptosis and inherited disorders.
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Lipid transport by mammalian ABC proteins
2011Co-Authors: Faraz Quazi, Robert S MoldayAbstract:ABC (ATP‑binding cassette) proteins actively transport a wide variety of substrates, including peptides, amino acids, sugars, metals, drugs, vitamins and lipids, across extracellular and intracellular membranes. Of the 49 human ABC proteins, a significant number are known to mediate the extrusion of lipids from membranes or the flipping of membrane lipids across the bilayer to generate and maintain membrane lipid asymmetry. Typical lipid substrates include phospholipids, sterols, sphingolipids, bile acids and related lipid conjugates. Members of the ABCA subfamily of ABC transporters and other ABC proteins such as ABCB4, ABCG1 and ABCG5/8 implicated in lipid transport play important roles in diverse biological processes such as cell signalling, membrane lipid asymmetry, removal of potentially toxic compounds and metabolites, and apoptosis. The importance of these ABC lipid transporters in cell physiology is evident from the finding that mutations in the genes encoding many of these proteins are responsible for severe inherited diseases. For example, mutations in ABCA1 cause Tangier disease associated with defective efflux of cholesterol and phosphatidylcholine from the plasma membrane to the lipid acceptor protein apoA1 (apolipoprotein AI), mutations in ABCA3 cause neonatal surfactant deficiency associated with a loss in secretion of the 1To whom correspondence should be addressed (emai
Nobuya Inagaki - One of the best experts on this subject based on the ideXlab platform.
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ABCA3 mediated choline phospholipids uptake into intracellular vesicles in a549 cells
FEBS Letters, 2007Co-Authors: Yoshihiro Matsumura, Nobuya Inagaki, Nobuhiro Ban, Hiromichi Sakai, Mayumi SasakiAbstract:ABCA3 is proposed to function as a lung surfactant lipid transporter. Here we report ABCA3-dependent lipid uptake into intracellular vesicles in lung adenocarcinoma A549 cells. A549 cells stably expressing GFP-tagged wild-type ABCA3 (A549/ABCA3WT) had larger LAMP3-positive vesicles than their parental cells as well as A549 cells expressing a Walker A motif mutant (A549/ABCA3N568D). The choline-phospholipids level in A549/ABCA3WT was increased 1.25-fold compared to that in A549 and A549/ABCA3N568D cells, while the cholesterol levels were similar. Sucrose gradient fractionation analysis in A549/ABCA3WT cells revealed that choline-phospholipids were enriched in low-density and nile red-positive vesicles. Electronmicroscopic analysis showed multilamellar vesicles in A549/ABCA3WT cells. These results indicate that ABCA3 mediates ATP-dependent choline-phospholipids uptake into intracellular vesicles.
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ABCA3 as a lipid transporter in pulmonary surfactant biogenesis
Journal of Biological Chemistry, 2007Co-Authors: Nobuhiro Ban, Hiroyuki Arai, Yoshihiro Matsumura, Hiromichi Sakai, Yasukazu Takanezawa, Mayumi Sasaki, Nobuya InagakiAbstract:Abstract ABCA3 protein is expressed predominantly at the limiting membrane of the lamellar bodies in alveolar type II cells, and mutations in the ABCA3 gene cause lethal respiratory distress in newborn infants. To investigate the function of ABCA3 protein, we generated ABCA3-deficient mice by targeting ABCA3. Full-term ABCA3–/– newborn pups died within an hour after birth because of acute respiratory failure. Ultrastructural analysis revealed abnormally dense lamellar body-like organelles and no normal lamellar bodies in ABCA3–/– alveolar type II cells. TLC and electrospray ionization mass spectrometry analyses of lipids in the pulmonary interstitium showed that phosphatidylcholine and phosphatidylglycerol, which contain palmitic acid and are abundant in normal surfactant lipids, were dramatically decreased in ABCA3–/– lung. These findings indicate that ABCA3 plays an essential role in pulmonary surfactant lipid metabolism and lamellar body biogenesis, probably by transporting these lipids as substrates.
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ABCA3 is a lamellar body membrane protein in human lung alveolar type ii cells1
FEBS Letters, 2001Co-Authors: Gen Yamano, Toshio Morohoshi, Hisayuki Funahashi, Yoshiyuki Uchida, Lixia Zhao, Seiji Shioda, Junichi Ogawa, Oichi Kawanami, Nobuya InagakiAbstract:Abstract The ABCA3 gene, of the ABCA subclass of ATP-binding cassette (ABC) transporters, is expressed exclusively in lung. We report here the cloning, molecular characterization, and distribution of human ABCA3 in the lung. Immunoblot analysis using the specific antibody reveals a 150-kDa protein in the crude membrane fraction of human lung. Immunohistochemical analyses of alveoli show that ABCA3 is expressed only in the type II cells expressing surfactant protein A. At the ultrastructural level, ABCA3 immunoreactivity was detected mostly at the limiting membrane of the lamellar bodies. Since members of the ABCA transporter family are known to be involved in transmembrane transport of endogenous lipids, our findings suggest that ABCA3 plays an important role in the formation of pulmonary surfactant in type II cells.
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atp binding cassette transporter abc2 abca2 in the rat brain a novel mammalian lysosome associated membrane protein and a specific marker for oligodendrocytes but not for myelin sheaths
The Journal of Neuroscience, 2001Co-Authors: Chengji J Zhou, Lixia Zhao, Nobuya Inagaki, Takahiro Hirabayashi, Jian Lian Guan, Shigeo Nakajo, Sakae Kikuyama, Seiji ShiodaAbstract:We recently cloned a full-length cDNA of the rat ATP-binding cassette transporter 2 (ABC2, or ABCA2) protein, a member of the ABC1 (or ABCA) subfamily (-ABC1/ABCA1 is a causal gene for Tangier disease) and found it to be strongly expressed in the rat brain. In this study, we identified ABC2 as a lysosome-associated membrane protein that is being localized specifically in oligodendrocytes. The ABC2-immunolabeled cells were detected mainly in the white matter but were also scattered in gray matter throughout the whole brain. In addition, these cells were found to be colocalized with 2',3'-cyclic nucleotide-3'-phosphodiesterase (CNPase) immunoreactivity when the marker antibody for oligodendrocytes was used. However, no such colocalization was observed with markers for other kinds of glial cells. Unlike the CNP antibody, which also intensely stains myelin sheaths in the white matter, ABC2 immunoreactivity was detected only in the cell bodies of oligodendrocytes. At the ultrastructural level, ABC2 immunoreactivity was detected mostly around lysosome and partly in Golgi apparatus by electron microscopy. This was confirmed by immunocolocalization of ABC2 and lysosomal markers in a neuroblastoma cell line. Immunoblotting analysis of ABC2 from the whole brain and the ABC2-transfected cell line revealed bands at approximately 260 kDa. The result of in situ hybridization with a riboprobe for ABC2 matched the results obtained from immunostaining. These findings strongly suggest that ABC2 is a specific marker for oligodendrocytes but not for myelinsheaths and that it is as a novel mammalian lysosome-associated membrane protein involved in myelinization or other kinds of metabolism in the CNS.
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cloning characterization and tissue distribution of the rat atp binding cassette abc transporter abc2 abca2
Biochemical Journal, 2000Co-Authors: Lixia Zhao, Kazumitsu Ueda, Seiji Shioda, Teruo Amachi, Chengji Zhou, Arowu Tanaka, Masanori Nakata, Takahiro Hirabayashi, Nobuya InagakiAbstract:: The ABC1 (ABCA) subfamily of the ATP-binding cassette (ABC) transporter superfamily has a structural feature that distinguishes it from other ABC transporters. Here we report the cloning, molecular characterization and tissue distribution of ABC2/ABCA2, which belongs to the ABC1 subfamily. Rat ABC2 is a protein of 2434 amino acids that has 44.5%, 40.0% and 40.8% identity with mouse ABC1/ABCA1, human ABC3/ABCA3 and human ABCR/ABCA4 respectively. Immunoblot analysis showed that proteins of 260 and 250 kDa were detected in COS-1 cells transfected with ABC2 having a haemagglutinin tag, while no band was detected in mock-transfected cells. After incubation with N-glycosidase F, the mobilities of the two proteins increased and a single band was detected, suggesting that ABC2 is a glycoprotein. Photoaffinity labelling with 8-azido-[alpha-(32)P]ATP confirmed that ATP binds to the ABC2 protein in the presence of Mg(2+). RNA blot analysis showed that ABC2 mRNA is most abundant in rat brain. Examination of brain by in situ hybridization determined that ABC2 is expressed at high levels in the white matter, indicating that it is expressed in the oligodendrocytes. ABC2, therefore, is a glycosylated ABC transporter protein, and may play an especially important role in the brain. In addition, the N-terminal 60-amino-acid sequence of the human ABC1, which was missing from previous reports, has been determined.
Jeffrey A. Whitsett - One of the best experts on this subject based on the ideXlab platform.
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fatal familial lung disease caused by ABCA3 deficiency without identified ABCA3 mutations
The Journal of Pediatrics, 2010Co-Authors: Adam W Gower, Jeffrey A. Whitsett, Susan E Wert, Jennifer S Ginsberg, Agneta Golan, Lawrence M NogeeAbstract:Objective To test the hypothesis that some functionally significant variants in the gene encoding member A3 of the ATP Binding Cassette family (ABCA3) are not detected using exon-based sequencing approaches. Study design The first of 2 female siblings who died from neonatal respiratory failure was examined for mutations with sequence analysis of all ABCA3 exons and known regulatory elements within the 5' untranslated region. Lung tissue from both siblings was immunostained for ABCA3 and examined with electron microscopy. Segregation of ABCA3 alleles was determined with analysis of polymorphisms in the parents and all children. Results No mutations were identified with ABCA3 sequence analysis in the first affected infant. Affected siblings were concordant for their ABCA3 alleles, but discordant from those of their unaffected siblings. ABCA3 protein was not detectable with immunostaining in lung tissue samples from both affected infants. Electron microscopy demonstrated small, dense lamellar bodies, characteristically seen with ABCA3 mutations. Conclusions The segregation of ABCA3 alleles, absence of ABCA3 immunostaining, lung pathology, and ultrastructural findings support genetic ABCA3 deficiency as the cause of lung disease in these 2 infants, despite the lack of an identified genetic variant.
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stat3 regulates ABCA3 expression and influences lamellar body formation in alveolar type ii cells
American Journal of Respiratory Cell and Molecular Biology, 2008Co-Authors: Yohei Matsuzaki, Jean C Clark, Machiko Ikegami, Valerie Besnard, Yan Xu, Susan E Wert, Jeffrey A. WhitsettAbstract:ATP-Binding Cassette A3 (ABCA3) is a lamellar body associated lipid transport protein required for normal synthesis and storage of pulmonary surfactant in type II cells in the alveoli. In this study, we demonstrate that STAT3, activated by IL-6, regulates ABCA3 expression in vivo and in vitro. ABCA3 mRNA and immunostaining were decreased in adult mouse lungs in which STAT3 was deleted from the respiratory epithelium (Stat3Δ/Δ mice). Consistent with the role of STAT3, intratracheal IL-6 induced ABCA3 expression in vivo. Decreased ABCA3 and abnormalities in the formation of lamellar bodies, the intracellular site of surfactant lipid storage, were observed in Stat3Δ/Δ mice. Expression of SREBP1a and 1c, SCAP, ABCA3, and AKT mRNAs was inhibited by deletion of Stat3 in type II cells isolated from Stat3Δ/Δ mice. The activities of PI3K and AKT were required for normal ABCA3 gene expression in vitro. AKT activation induced SREBP expression and increased the activity of the ABCA3 promoter in vitro, consistent with...
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stat3 regulates ABCA3 expression and influences lamellar body formation in alveolar type ii cells
American Journal of Respiratory Cell and Molecular Biology, 2008Co-Authors: Yohei Matsuzaki, Jean C Clark, Machiko Ikegami, Valerie Besnard, Yan Xu, Susan E Wert, Jeffrey A. WhitsettAbstract:ATP-Binding Cassette A3 (ABCA3) is a lamellar body associated lipid transport protein required for normal synthesis and storage of pulmonary surfactant in type II cells in the alveoli. In this study, we demonstrate that STAT3, activated by IL-6, regulates ABCA3 expression in vivo and in vitro. ABCA3 mRNA and immunostaining were decreased in adult mouse lungs in which STAT3 was deleted from the respiratory epithelium (Stat3Δ/Δ mice). Consistent with the role of STAT3, intratracheal IL-6 induced ABCA3 expression in vivo. Decreased ABCA3 and abnormalities in the formation of lamellar bodies, the intracellular site of surfactant lipid storage, were observed in Stat3Δ/Δ mice. Expression of SREBP1a and 1c, SCAP, ABCA3, and AKT mRNAs was inhibited by deletion of Stat3 in type II cells isolated from Stat3Δ/Δ mice. The activities of PI3K and AKT were required for normal ABCA3 gene expression in vitro. AKT activation induced SREBP expression and increased the activity of the ABCA3 promoter in vitro, consistent with...
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ABCA3 mutations associated with pediatric interstitial lung disease
American Journal of Respiratory and Critical Care Medicine, 2005Co-Authors: Janine E Bullard, Jeffrey A. Whitsett, Michael Dean, Susan E Wert, Lawrence M NogeeAbstract:Rationale: ABCA3 is a member of the ATP-binding cassette family of proteins that mediate the translocation of a wide variety of substrates, including lipids, across cellular membranes. Mutations in the gene encoding ABCA3 were recently identified in full-term neonates with fatal surfactant deficiency. Objective: To test the hypothesis that ABCA3 mutations are not always associated with fatal neonatal lung disease but are a cause of pediatric interstitial lung disease. Methods: DNA samples were obtained from 195 children with chronic lung disease of unknown etiology. The 30 coding exons of the ABCA3 gene were sequenced in four unrelated children with a referring diagnosis of desquamative interstitial pneumonitis and who were older than 10 years at the time of enrollment. Results: Three of four patients (ages 16, 23, and 11 years) with desquamative interstitial pneumonitis had ABCA3 mutations identified on both alleles. All three had the same missense mutation (E292V) and a second unique mutation. The E292V mutation was not found on 200 control alleles from adults without lung disease, but seven additional patients of the remaining study patients had the E292V mutation on one allele. Immunohistochemical analysis of surfactant protein expression in three patients revealed a specific staining pattern for surfactant protein-B, which was the same pattern observed in several infants with fatal lung disease due to ABCA3 mutations. Conclusion: ABCA3 mutations cause some types of interstitial lung disease in pediatric patients.
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ABCA3 gene mutations in newborns with fatal surfactant deficiency
The New England Journal of Medicine, 2004Co-Authors: Sergey Shulenin, Tarmo Annilo, Jeffrey A. Whitsett, Susan E Wert, Lawrence M Nogee, Michael DeanAbstract:background Pulmonary surfactant forms a lipid-rich monolayer that coats the airways of the lung and is essential for proper inflation and function of the lung. Surfactant is produced by alveolar type II cells, stored intracellularly in organelles known as lamellar bodies, and secreted by exocytosis. The gene for ATP-binding cassette transporter A3 (ABCA3) is expressed in alveolar type II cells, and the protein is localized to lamellar bodies, suggesting that it has an important role in surfactant metabolism. methods We sequenced each of the coding exons of the ABCA3 gene in blood DNA from 21 racially and ethnically diverse infants with severe neonatal surfactant deficiency for which the etiologic process was unknown. Lung tissue from four patients was examined by high-resolution light and electron microscopy. results Nonsense and frameshift mutations, as well as mutations in highly conserved residues and in splice sites of the ABCA3 gene were identified in 16 of the 21 patients (76 percent). In five consanguineous families with mutations, each pair of siblings was homozygous for the same mutation and each mutation was found in only one family. Markedly abnormal lamellar bodies were observed by ultrastructural examination of lung tissue from four patients with different ABCA3 mutations, including nonsense, splice-site, and missense mutations. conclusions Mutation of the ABCA3 gene causes fatal surfactant deficiency in newborns. ABCA3 is critical for the proper formation of lamellar bodies and surfactant function and may also be important for lung function in other pulmonary diseases. Since it is closely related to ABCA1 and ABCA4, proteins that transport phospholipids in macrophages and photoreceptor cells, it may have a role in surfactant phospholipid metabolism.
Faraz Quazi - One of the best experts on this subject based on the ideXlab platform.
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differential phospholipid substrates and directional transport by atp binding cassette proteins abca1 abca7 and abca4 and disease causing mutants
Journal of Biological Chemistry, 2013Co-Authors: Faraz Quazi, Robert S MoldayAbstract:Abstract ABCA1, ABCA7, and ABCA4 are members of the ABCA subfamily of ATP-binding cassette transporters which share extensive sequence and structural similarity. Mutations in ABCA1 cause Tangier disease characterized by defective cholesterol homeostasis and high-density lipoprotein (HDL) deficiency. Mutations in ABCA4 are responsible for Stargardt disease, a degenerative disorder associated with severe loss in central vision. Although cell-based studies have implicated ABCA proteins in lipid transport, the substrates and direction of transport have not been firmly established. We have purified and reconstituted ABCA1, ABCA7 and ABCA4 into liposomes for fluorescent-lipid transport studies. ABCA1 actively exported or flipped phosphatidylcholine (PC), phosphatidylserine (PS), and sphingomyelin (SM) from the cytoplasmic to the exocytoplasmic leaflet of membranes, whereas ABCA7 preferentially exported PS. In contrast ABCA4 transported phosphatidylethanolamine (PE) in the reverse direction. The same phospholipids stimulated the ATPase activity of these ABCA transporters. The transport activity and ATPase activity of ABCA1 and ABCA4 was reduced by 25% in the presence of 20% cholesterol. Nine ABCA1 Tangier mutants and corresponding ABCA4 Stargardt mutants showed significantly reduced phospholipid transport activity and subcellular mislocalization. These studies provide the first direct evidence for ABCA1 and ABCA7 functioning as phospholipid transporters and suggest that this activity is an essential step in the loading of ApoA-1 with phospholipids for HDL formation.
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differential phospholipid substrates and directional transport by atp binding cassette proteins abca1 abca7 and abca4 and disease causing mutants
Journal of Biological Chemistry, 2013Co-Authors: Faraz Quazi, Robert S MoldayAbstract:ABCA1, ABCA7, and ABCA4 are members of the ABCA subfamily of ATP-binding cassette transporters that share extensive sequence and structural similarity. Mutations in ABCA1 cause Tangier disease characterized by defective cholesterol homeostasis and high density lipoprotein (HDL) deficiency. Mutations in ABCA4 are responsible for Stargardt disease, a degenerative disorder associated with severe loss in central vision. Although cell-based studies have implicated ABCA proteins in lipid transport, the substrates and direction of transport have not been firmly established. We have purified and reconstituted ABCA1, ABCA7, and ABCA4 into liposomes for fluorescent-lipid transport studies. ABCA1 actively exported or flipped phosphatidylcholine, phosphatidylserine, and sphingomyelin from the cytoplasmic to the exocytoplasmic leaflet of membranes, whereas ABCA7 preferentially exported phosphatidylserine. In contrast, ABCA4 transported phosphatidylethanolamine in the reverse direction. The same phospholipids stimulated the ATPase activity of these ABCA transporters. The transport and ATPase activities of ABCA1 and ABCA4 were reduced by 25% in the presence of 20% cholesterol. Nine ABCA1 Tangier mutants and the corresponding ABCA4 Stargardt mutants showed significantly reduced phospholipid transport activity and subcellular mislocalization. These studies provide the first direct evidence for ABCA1 and ABCA7 functioning as phospholipid transporters and suggest that this activity is an essential step in the loading of apoA-1 with phospholipids for HDL formation.
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Lipid transport by mammalian ABC proteins.
Essays in biochemistry, 2011Co-Authors: Faraz Quazi, Robert S MoldayAbstract:ABC (ATP-binding cassette) proteins actively transport a wide variety of substrates, including peptides, amino acids, sugars, metals, drugs, vitamins and lipids, across extracellular and intracellular membranes. Of the 49 hum an ABC proteins, a significant number are known to mediate the extrusion of lipids from membranes or the flipping of membrane lipids across the bilayer to generate and maintain membrane lipid asymmetry. Typical lipid substrates include phospholipids, sterols, sphingolipids, bile acids and related lipid conjugates. Members of the ABCA subfamily of ABC transporters and other ABC proteins such as ABCB4, ABCG1 and ABCG5/8 implicated in lipid transport play important roles in diverse biological processes such as cell signalling, membrane lipid asymmetry, removal of potentially toxic compounds and metabolites, and apoptosis. The importance of these ABC lipid transporters in cell physiology is evident from the finding that mutations in the genes encoding many of these proteins are responsible for severe inherited diseases. For example, mutations in ABCA1 cause Tangier disease associated with defective efflux of cholesterol and phosphatidylcholine from the plasma membrane to the lipid acceptor protein apoA1 (apolipoprotein AI), mutations in ABCA3 cause neonatal surfactant deficiency associated with a loss in secretion of the lipid pulmonary surfactants from lungs of newborns, mutations in ABCA4 cause Stargardt macular degeneration, a retinal degenerative disease linked to the reduced clearance of retinoid compounds from photoreceptor cells, mutations in ABCA12 cause harlequin and lamellar ichthyosis, skin diseases associated with defective lipid trafficking in keratinocytes, and mutations in ABCB4 and ABCG5/ABCG8 are responsible for progressive intrafamilial hepatic disease and sitosterolaemia associated with defective phospholipid and sterol transport respectively. This chapter highlights the involvement of various mammalian ABC transporters in lipid transport in the context of their role in cell signalling, cellular homoeostasis, apoptosis and inherited disorders.
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Lipid transport by mammalian ABC proteins
2011Co-Authors: Faraz Quazi, Robert S MoldayAbstract:ABC (ATP‑binding cassette) proteins actively transport a wide variety of substrates, including peptides, amino acids, sugars, metals, drugs, vitamins and lipids, across extracellular and intracellular membranes. Of the 49 human ABC proteins, a significant number are known to mediate the extrusion of lipids from membranes or the flipping of membrane lipids across the bilayer to generate and maintain membrane lipid asymmetry. Typical lipid substrates include phospholipids, sterols, sphingolipids, bile acids and related lipid conjugates. Members of the ABCA subfamily of ABC transporters and other ABC proteins such as ABCB4, ABCG1 and ABCG5/8 implicated in lipid transport play important roles in diverse biological processes such as cell signalling, membrane lipid asymmetry, removal of potentially toxic compounds and metabolites, and apoptosis. The importance of these ABC lipid transporters in cell physiology is evident from the finding that mutations in the genes encoding many of these proteins are responsible for severe inherited diseases. For example, mutations in ABCA1 cause Tangier disease associated with defective efflux of cholesterol and phosphatidylcholine from the plasma membrane to the lipid acceptor protein apoA1 (apolipoprotein AI), mutations in ABCA3 cause neonatal surfactant deficiency associated with a loss in secretion of the 1To whom correspondence should be addressed (emai
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the role of the photoreceptor abc transporter abca4 in lipid transport and stargardt macular degeneration
Biochimica et Biophysica Acta, 2009Co-Authors: Robert S Molday, Ming Zhong, Faraz QuaziAbstract:Abstract ABCA4 is a member of the ABCA subfamily of ATP binding cassette (ABC) transporters that is expressed in rod and cone photoreceptors of the vertebrate retina. ABCA4, also known as the Rim protein and ABCR, is a large 2273 amino acid glycoprotein organized as two tandem halves, each containing a single membrane spanning segment followed sequentially by a large exocytoplasmic domain, a multispanning membrane domain and a nucleotide binding domain. Over 500 mutations in the gene encoding ABCA4 are associated with a spectrum of related autosomal recessive retinal degenerative diseases including Stargardt macular degeneration, cone–rod dystrophy and a subset of retinitis pigmentosa. Biochemical studies on the purified ABCA4 together with analysis of abca4 knockout mice and patients with Stargardt disease have implicated ABCA4 as a retinylidene-phosphatidylethanolamine transporter that facilitates the removal of potentially reactive retinal derivatives from photoreceptors following photoexcitation. Knowledge of the genetic and molecular basis for ABCA4 related retinal degenerative diseases is being used to develop rationale therapeutic treatments for this set of disorders.
