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Liu T, Zhao J, Feng JY, Lu Y, Sheps JA, Wang RX, Han J, Ling V, Wang JS. Neonatal Dubin-Johnson Syndrome and its Differentiation from Biliary Atresia. J Clin Transl Hepatol 2023; 11:163-173. [PMID: 36406324 PMCID: PMC9647112 DOI: 10.14218/jcth.2021.00460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 01/18/2022] [Accepted: 02/22/2022] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND AND AIMS The aim was to determine if liver biochemistry indices can be used as biomarkers to help differentiate patients with neonatal Dubin-Johnson syndrome (nDJS) from those with biliary atresia (BA). METHODS Patients with genetically-confirmed nDJS or cholangiographically confirmed BA were retrospectively enrolled and randomly assigned to discovery or verification cohorts. Their liver chemistries, measured during the neonatal period, were compared. Predictive values were calculated by receiver operating characteristic curve analysis. RESULTS A cohort of 53 nDJS patients was recruited, of whom 13 presented with acholic stools, and 14 underwent diagnostic cholangiography or needle liver biopsy to differentiate from BA. Thirty-five patients in the cohort, with complete biochemical information measured during the neonatal period, were compared with 133 infants with cholangiographically confirmed BA. Total and direct bilirubin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bile acids, alkaline phosphatase, and gamma-glutamyl transferase were significantly lower in nDJS than in BA. In the discovery cohort, the areas under the curve for ALT and AST were 0.908 and 0.943, respectively. In the validation cohort, 13/15 patients in the nDJS group were classified as nDJS, and 10/53 in the BA control group were positive (p<0.00001) with an ALT biomarker cutoff value of 75 IU/L. Thirteen of 15 patients were classified as nDJS and none were classified positive in the BA group (13/15 vs. 0/53, p<0.00001) with an AST cutoff of 87 IU/L. CONCLUSIONS Having assembled and investigated the largest cohort of nDJS patients reported to date, we found that nDJS patients could be distinguished from BA patients using the serum AST level as a biomarker. The finding may be clinically useful to spare cholestatic nDJS patients unnecessary invasive procedures.
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Affiliation(s)
- Teng Liu
- The Center for Pediatric Liver Diseases, Children’s Hospital of Fudan University, Shanghai, China
- Correspondence to: Teng Liu and Jian-She Wang, The Center for Pediatric Liver Diseases, Children’s Hospital of Fudan University, NO. 399 Wanyuan Road, Minhang District, Shanghai 201102, China. ORCID: https://orcid.org/0000-0002-0858-2151 (TL), https://orcid.org/0000-0003-0823-586X (JSW). Tel: +86-21-64931171, E-mail: (TL), (JSW)
| | - Jing Zhao
- The Center for Pediatric Liver Diseases, Children’s Hospital of Fudan University, Shanghai, China
| | - Jia-Yan Feng
- The Department of Pathology, Children’s Hospital of Fudan University, Shanghai, China
| | - Yi Lu
- The Center for Pediatric Liver Diseases, Children’s Hospital of Fudan University, Shanghai, China
| | | | - Ren-Xue Wang
- BC Cancer Agency, Vancouver, British Columbia, V5Z 1L3, Canada
| | - Jun Han
- University of Victoria-Genome BC Proteomics Center, University of Victoria, Victoria, British Columbia, V8Z 7X8, Canada
| | - Victor Ling
- BC Cancer Agency, Vancouver, British Columbia, V5Z 1L3, Canada
| | - Jian-She Wang
- The Center for Pediatric Liver Diseases, Children’s Hospital of Fudan University, Shanghai, China
- Shanghai Key Laboratory of Birth Defects, Shanghai, China
- Correspondence to: Teng Liu and Jian-She Wang, The Center for Pediatric Liver Diseases, Children’s Hospital of Fudan University, NO. 399 Wanyuan Road, Minhang District, Shanghai 201102, China. ORCID: https://orcid.org/0000-0002-0858-2151 (TL), https://orcid.org/0000-0003-0823-586X (JSW). Tel: +86-21-64931171, E-mail: (TL), (JSW)
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Sheps JA, Wang R, Wang J, Ling V. The protective role of hydrophilic tetrahydroxylated bile acids (THBA). Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1866:158925. [PMID: 33713832 DOI: 10.1016/j.bbalip.2021.158925] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Revised: 02/21/2021] [Accepted: 03/05/2021] [Indexed: 01/14/2023]
Abstract
Bile acids are key components of bile required for human health. In humans and mice, conditions of reduced bile flow, cholestasis, induce bile acid detoxification by producing tetrahydroxylated bile acids (THBA), more hydrophilic and less cytotoxic than the usual bile acids, which are typically di- or tri-hydroxylated. Mice deficient in the Bile Salt Export Pump (Bsep, or Abcb11), the primary bile acid transporter in liver cells, produce high levels of THBA, and avoid the severe liver damage typically seen in humans with BSEP deficiencies. THBA can suppress bile acid-induced liver damage in Mdr2-deficient mice, caused by their lack of phospholipids in bile exposing their biliary tracts to unbound bile acids. Here we review THBA-related works in both animals and humans, and discuss their potential relevance and applications as a class of functional bile acids.
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Affiliation(s)
- Jonathan A Sheps
- BC Cancer Research Centre, BC Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada
| | - Renxue Wang
- BC Cancer Research Centre, BC Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada
| | - Jianshe Wang
- Department of Pediatrics, Fudan University Shanghai Medical College, The Center for Pediatric Liver Diseases, Children's Hospital of Fudan University, Shanghai 201102, China
| | - Victor Ling
- BC Cancer Research Centre, BC Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia Vancouver, British Columbia, Canada.
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Wang R, Sheps JA, Liu L, Han J, Chen PSK, Lamontagne J, Wilson PD, Welch I, Borchers CH, Ling V. Hydrophilic bile acids prevent liver damage caused by lack of biliary phospholipid in Mdr2-/- mice. J Lipid Res 2019; 60:85-97. [PMID: 30416103 PMCID: PMC6314265 DOI: 10.1194/jlr.m088070] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 11/04/2018] [Indexed: 12/15/2022] Open
Abstract
Bile acid imbalance causes progressive familial intrahepatic cholestasis type 2 (PFIC2) or type 3 (PFIC3), severe liver diseases associated with genetic defects in the biliary bile acid transporter bile salt export pump (BSEP; ABCB11) or phosphatidylcholine transporter multidrug resistance protein 3 (MDR3; ABCB4), respectively. Mdr2-/- mice (a PFIC3 model) develop progressive cholangitis, ductular proliferation, periportal fibrosis, and hepatocellular carcinoma (HCC) because the nonmicelle-bound bile acids in the bile of these mice are toxic. We asked whether the highly hydrophilic bile acids generated by Bsep-/- mice could protect Mdr2-/- mice from progressive liver damage. We generated double-KO (DKO: Bsep-/- and Mdr2-/- ) mice. Their bile acid composition resembles that of Bsep-/- mice, with increased hydrophilic muricholic acids, tetrahydroxylated bile acids (THBAs), and reduced hydrophobic cholic acid. These mice lack the liver pathology of their Mdr2-/- littermates. The livers of DKO mice have gene expression profiles very similar to Bsep-/- mice, with 4,410 of 6,134 gene expression changes associated with the Mdr2-/- mutation being suppressed. Feeding with THBAs partially alleviates liver damage in the Mdr2-/- mice. Hydrophilic changes to biliary bile acid composition, including introduction of THBA, can prevent the progressive liver pathology associated with the Mdr2-/- (PFIC3) mutation.
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Affiliation(s)
- Renxue Wang
- BC Cancer Research Centre, Vancouver, British Columbia, Canada
| | | | - Lin Liu
- BC Cancer Research Centre, Vancouver, British Columbia, Canada
| | - Jun Han
- University of Victoria-Genome BC Proteomics Centre University of Victoria, Victoria, British Columbia, Canada
| | - Patrick S K Chen
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Jason Lamontagne
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Peter D Wilson
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Ian Welch
- Department of Pathology University of British Columbia, Vancouver, British Columbia, Canada
- Centre for Comparative Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Christoph H Borchers
- University of Victoria-Genome BC Proteomics Centre University of Victoria, Victoria, British Columbia, Canada
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
- Proteomics Centre, Segal Cancer Centre, Lady Davis Institute, Jewish General Hospital, McGill University, Montreal, Quebec, Canada
| | - Victor Ling
- BC Cancer Research Centre, Vancouver, British Columbia, Canada
- Department of Pathology University of British Columbia, Vancouver, British Columbia, Canada
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4
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Qiu Y, Gong J, Feng J, Wang R, Han J, Liu T, Lu Y, Li L, Zhang M, Sheps JA, Wang N, Yan Y, Li J, Chen L, Borchers CH, Sipos B, Knisely A, Ling V, Xing Q, Wang J. Defects in myosin VB are associated with a spectrum of previously undiagnosed low γ-glutamyltransferase cholestasis. Hepatology 2017; 65:1655-1669. [PMID: 28027573 PMCID: PMC5413810 DOI: 10.1002/hep.29020] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 11/16/2016] [Accepted: 12/21/2016] [Indexed: 12/11/2022]
Abstract
Hereditary cholestasis in childhood and infancy with normal serum gamma-glutamyltransferase (GGT) activity is linked to several genes. Many patients, however, remain genetically undiagnosed. Defects in myosin VB (MYO5B; encoded by MYO5B) cause microvillus inclusion disease (MVID; MIM251850) with recurrent watery diarrhea. Cholestasis, reported as an atypical presentation in MVID, has been considered a side effect of parenteral alimentation. Here, however, we report on 10 patients who experienced cholestasis associated with biallelic, or suspected biallelic, mutations in MYO5B and who had neither recurrent diarrhea nor received parenteral alimentation. Seven of them are from two study cohorts, together comprising 31 undiagnosed low-GGT cholestasis patients; 3 are sporadic. Cholestasis in 2 patients was progressive, in 3 recurrent, in 2 transient, and in 3 uncategorized because of insufficient follow-up. Liver biopsy specimens revealed giant-cell change of hepatocytes and intralobular cholestasis with abnormal distribution of bile salt export pump (BSEP) at canaliculi, as well as coarse granular dislocation of MYO5B. Mass spectrometry of plasma demonstrated increased total bile acids, primary bile acids, and conjugated bile acids, with decreased free bile acids, similar to changes in BSEP-deficient patients. Literature review revealed that patients with biallelic mutations predicted to eliminate MYO5B expression were more frequent in typical MVID than in isolated-cholestasis patients (11 of 38 vs. 0 of 13). CONCLUSION MYO5B deficiency may underlie 20% of previously undiagnosed low-GGT cholestasis. MYO5B deficiency appears to impair targeting of BSEP to the canalicular membrane with hampered bile acid excretion, resulting in a spectrum of cholestasis without diarrhea. (Hepatology 2017;65:1655-1669).
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Affiliation(s)
- Yi‐Ling Qiu
- The Center for Pediatric Liver DiseasesChildren's Hospital of Fudan UniversityShanghaiChina
| | - Jing‐Yu Gong
- Department of PediatricsJinshan Hospital of Fudan UniversityShanghaiChina
| | - Jia‐Yan Feng
- Department of PathologyChildren's Hospital of Fudan UniversityShanghaiChina
| | | | - Jun Han
- University of Victoria−Genome BC Proteomics CentreUniversity of VictoriaVictoriaBritish ColumbiaCanada
| | - Teng Liu
- Department of PediatricsJinshan Hospital of Fudan UniversityShanghaiChina
| | - Yi Lu
- The Center for Pediatric Liver DiseasesChildren's Hospital of Fudan UniversityShanghaiChina
| | - Li‐Ting Li
- The Center for Pediatric Liver DiseasesChildren's Hospital of Fudan UniversityShanghaiChina
| | - Mei‐Hong Zhang
- Department of PediatricsJinshan Hospital of Fudan UniversityShanghaiChina
| | | | - Neng‐Li Wang
- Department of PediatricsJinshan Hospital of Fudan UniversityShanghaiChina
| | - Yan‐Yan Yan
- Department of PediatricsJinshan Hospital of Fudan UniversityShanghaiChina
| | - Jia‐Qi Li
- Department of PediatricsJinshan Hospital of Fudan UniversityShanghaiChina
| | - Lian Chen
- Department of PathologyChildren's Hospital of Fudan UniversityShanghaiChina
| | - Christoph H. Borchers
- University of Victoria−Genome BC Proteomics CentreUniversity of VictoriaVictoriaBritish ColumbiaCanada
| | - Bence Sipos
- Institute of General Pathology and NeuropathologyTübingen University HospitalTübingenGermany
| | - A.S. Knisely
- Institute of PathologyGraz Medical UniversityGrazAustria
| | - Victor Ling
- BC Cancer AgencyVancouverBritish ColumbiaCanada
| | - Qing‐He Xing
- Institutes of Biomedical Sciences of Fudan UniversityShanghaiChina
| | - Jian‐She Wang
- Department of PediatricsJinshan Hospital of Fudan UniversityShanghaiChina
- Department of Infectious DiseasesChildren's Hospital of Fudan UniversityShanghaiChina
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Wang R, Liu L, Sheps JA, Forrest D, Hofmann AF, Hagey LR, Ling V. Defective canalicular transport and toxicity of dietary ursodeoxycholic acid in the abcb11-/- mouse: transport and gene expression studies. Am J Physiol Gastrointest Liver Physiol 2013; 305:G286-94. [PMID: 23764895 DOI: 10.1152/ajpgi.00082.2013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The bile salt export pump (BSEP), encoded by the abcb11 gene, is the major canalicular transporter of bile acids from the hepatocyte. BSEP malfunction in humans causes bile acid retention and progressive liver injury, ultimately leading to end-stage liver failure. The natural, hydrophilic, bile acid ursodeoxycholic acid (UDCA) is efficacious in the treatment of cholestatic conditions, such as primary biliary cirrhosis and cholestasis of pregnancy. The beneficial effects of UDCA include promoting bile flow, reducing hepatic inflammation, preventing apoptosis, and maintaining mitochondrial integrity in hepatocytes. However, the role of BSEP in mediating UDCA efficacy is not known. Here, we used abcb11 knockout mice (abcb11-/-) to test the effects of acute and chronic UDCA administration on biliary secretion, bile acid composition, liver histology, and liver gene expression. Acutely infused UDCA, or its taurine conjugate (TUDC), was taken up by the liver but retained, with negligible biliary output, in abcb11-/- mice. Feeding UDCA to abcb11-/- mice led to weight loss, retention of bile acids, elevated liver enzymes, and histological damage to the liver. Semiquantitative RT-PCR showed that genes encoding Mdr1a and Mdr1b (canalicular) as well as Mrp4 (basolateral) transporters were upregulated in abcb11-/- mice. We concluded that infusion of UDCA and TUDC failed to induce bile flow in abcb11-/- mice. UDCA fed to abcb11-/- mice caused liver damage and the appearance of biliary tetra- and penta-hydroxy bile acids. Supplementation with UDCA in the absence of Bsep caused adverse effects in abcb11-/- mice.
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Affiliation(s)
- Renxue Wang
- British Columbia Cancer Research Centre, 675 W. 10 Ave., Vancouver, BC, Canada V5Z 1L3.
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Wang R, Sheps JA, Ling V. ABC transporters, bile acids, and inflammatory stress in liver cancer. Curr Pharm Biotechnol 2011; 12:636-46. [PMID: 21118090 DOI: 10.2174/138920111795163986] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 04/10/2010] [Indexed: 11/22/2022]
Abstract
The biliary secretion of bile acids is critical for multiple liver functions including digesting fatty nutrients and driving bile flow. When this process is impaired, the accumulating bile acids cause inflammatory liver injury. Multiple ABC transporters in the liver are key players to safeguard the hepatocyte and avoid toxicity due to bile acid over-accumulation. BSEP provides for efficient secretion of bile acids across the canalicular membrane against a steep concentration gradient. MDR3/Mdr2 and ABCG5/G8 secrete phosphatidylcholine and cholesterol, respectively, in coordination with BSEP-mediated bile acid secretion to mask the detergent/toxic effects of bile acids in the bile ductular space. Several lines of evidence indicate that when these critical steps are compromised, bile acid toxicity in vivo leads to inflammatory liver injury and liver cancer. In bsep-/- mice, liver cancer is rare. These mice display greatly increased expression of alternative bile acid transporters, such as Mdr1a/1b, Mrp3 and Mrp4. We believe these alternative transport systems provide an additional safeguard to avoid bile acid overload in liver. Such backup systems appear to be under-utilized in humans, as defects in BSEP and MDR3 lead to severe, often fatal childhood diseases. It is possible, therefore, that targeting ABC transporters and modulating the toxicity of the bile acid pool could be vital interventions to alleviate chronic inflammation and reduce the incidence of liver cancer in high-risk populations. The combination of an alternative ABC transporter with a novel substrate may prove an effective chemo-preventive or therapeutic strategy.
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Affiliation(s)
- Renxue Wang
- British Columbia Cancer Research Centre, British Columbia Cancer Agency, Vancouver, British Columbia, V5Z 1L3, Canada.
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Abstract
UNLABELLED Bile salt export pump (BSEP; ATP-binding cassette, subfamily B, member 11) mutations in humans result in progressive familial intrahepatic cholestasis type 2, a fatal liver disease with greatly reduced bile flow. However in mice, Bsep knockout leads only to mild cholestasis with substantial bile flow and up-regulated P-glycoprotein genes (multidrug resistance protein 1a [Mdr1a] and Mdr1b). To determine whether P-glycoprotein is responsible for the relatively mild phenotype observed in Bsep knockout mice, we have crossed mouse strains knocked out for Bsep and the two P-glycoprotein genes and generated a triple knockout mouse. We found that a knockout of the three genes leads to a significantly more severe phenotype with impaired bile formation, jaundice, flaccid gallbladder, and increased mortality. The triple knockout mouse is the most severe genetic model of intrahepatic cholestasis yet developed. CONCLUSION P-glycoprotein functions as a critical compensatory mechanism, which reduces the severity of cholestasis in Bsep knockout mice.
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Affiliation(s)
- Renxue Wang
- British Columbia Cancer Research Centre, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
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Affiliation(s)
- Jonathan A Sheps
- Cancer Genetics and Developmental Biology, BC Cancer Research Centre, British Columbia Cancer Agency, Vancouver, BC V5Z 1L3 Canada.
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Zhao Z, Thomas JH, Chen N, Sheps JA, Baillie DL. Comparative genomics and adaptive selection of the ATP-binding-cassette gene family in caenorhabditis species. Genetics 2007; 175:1407-18. [PMID: 17194779 PMCID: PMC1840077 DOI: 10.1534/genetics.106.066720] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2006] [Accepted: 12/24/2006] [Indexed: 11/18/2022] Open
Abstract
ABC transporters constitute one of the largest gene families in all species. They are mostly involved in transport of substrates across membranes. We have previously demonstrated that the Caenorhabditis elegans ABC family shows poor one-to-one gene orthology with other distant model organisms. To address the evolution dynamics of this gene family among closely related species, we carried out a comparative analysis of the ABC family among the three nematode species C. elegans, C. briggsae, and C. remanei. In contrast to the previous observations, the majority of ABC genes in the three species were found in orthologous trios, including many tandemly duplicated ABC genes, indicating that the gene duplication took place before speciation. Species-specific expansions of ABC members are rare and mostly observed in subfamilies A and B. C. briggsae and C. remanei orthologous ABC genes tend to cluster on trees, with those of C. elegans as an outgroup, consistent with their proposed species phylogeny. Comparison of intron/exon structures of the highly conserved ABCE subfamily members also indicates a closer relationship between C. briggsae and C. remanei than between either of these species and C. elegans. A comparison between insect and mammalian species indicates lineage-specific duplications or deletions of ABC genes, while the family size remains relatively constant. Sites undergoing positive selection within subfamily D, which are implicated in very-long-chain fatty acid transport, were identified. The evolution of these sites might be driven by the changes in food source with time.
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Affiliation(s)
- Zhongying Zhao
- British Columbia Cancer Research Center, Vancouver, British Columbia V5Z 1L6, Canada.
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Abstract
The problem of multidrug resistance (MDR) in human cancers led to the discovery 30 years ago of a single protein P-glycoprotein (P-gp), capable of mediating resistance to multiple structurally diverse drugs. P-gp became the archetypal eukaryotic ABC transporter gene, and studies of P-gp and related ABC transporters in both eukaryotes and bacteria have led to a basic mechanistic understanding of the molecular basis of MDR. Particular milestones along the way have been the identification of the homology between P-gp and bacterial transport proteins, the purification and functional reconstitution of P-gp into synthetic lipid systems, and the development of targeted therapies that attempt to overcome MDR by inhibiting P-gp. This preface places into this context some of the less well-explored themes developed in the MDR field, particularly various alternative models of P-gp action, evidence for parallel physiological roles for P-gp, and the unusual relationship between the substrate recognition capabilities of ABC transporters and their evolutionary history.
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Abstract
Genetic analysis of the nematode Caenorhabditis elegans reveals that all dpy-5 alleles are dominant suppressors of bli-4 blistering. Molecular cloning of dpy-5 establishes that it encodes a cuticle procollagen, defects in which are responsible for the short-body, dumpy phenotype. The null mutation, e907 removes the entire coding region, whereas the dpy-5 reference allele, e61, contains a nonsense substitution. RT-PCR analysis and a dpy-5::gfp fusion show that dpy-5 is expressed only in hypodermal cells at all post-embryonic life-cycle stages. Variable expression of dpy-5 in V lineage-derived seam cells suggests an alternative regulatory mechanism in these cells. The dpy-5 gene product contains an Arg-X-X-Arg cleavage motif that could be recognized by a proprotein convertase, such as BLI-4. Mutation of this site cause a dominant dumpy phenotype suggesting Dpy-5 procollagen requires processing for normal cuticle production.
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Affiliation(s)
- C Thacker
- Department of Medical Genetics, University of British Columbia, 419-2125 East Mall, Vancouver, B.C., V6T 1Z4, Canada
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Zhao Z, Sheps JA, Ling V, Fang LL, Baillie DL. Expression analysis of ABC transporters reveals differential functions of tandemly duplicated genes in Caenorhabditis elegans. J Mol Biol 2004; 344:409-17. [PMID: 15522294 DOI: 10.1016/j.jmb.2004.09.052] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2004] [Revised: 09/21/2004] [Accepted: 09/21/2004] [Indexed: 01/08/2023]
Abstract
We have previously identified 60 predicted ABC transporter genes in the Caenorhabditis elegans genome and classified them into eight groups. As an initial step towards understanding how these putative ABC genes work in worms, we generated promoter-fluorescent protein fusions for the entire family to address when and where these genes are turned on in vivo. Both Aequoria green fluorescent protein (GFP) and Discosoma red fluorescent protein (RFP) were used as reporters in our transgenic assay. Observable expression is more frequently seen from fusions to genes in subfamilies B, C, D and E than those in subfamilies A and G. Sixteen worm ABC genes are found in tandem duplications, forming two four-gene clusters and four two-gene clusters. Fifteen out of the 16 duplicated gene promoters drove different or partially overlapping expression patterns, suggesting active functions for these duplicated genes. Furthermore, our results suggest that an internal promoter can cause differential expression of genes within an operon. Finally, our observations suggest that it is possible for coding sequences to function as a regulatory region for a neighbouring gene.
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Affiliation(s)
- Zhongying Zhao
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
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13
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Sheps JA, Ralph S, Zhao Z, Baillie DL, Ling V. The ABC transporter gene family of Caenorhabditis elegans has implications for the evolutionary dynamics of multidrug resistance in eukaryotes. Genome Biol 2004; 5:R15. [PMID: 15003118 PMCID: PMC395765 DOI: 10.1186/gb-2004-5-3-r15] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2003] [Revised: 11/27/2003] [Accepted: 01/13/2004] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Many drugs of natural origin are hydrophobic and can pass through cell membranes. Hydrophobic molecules must be susceptible to active efflux systems if they are to be maintained at lower concentrations in cells than in their environment. Multi-drug resistance (MDR), often mediated by intrinsic membrane proteins that couple energy to drug efflux, provides this function. All eukaryotic genomes encode several gene families capable of encoding MDR functions, among which the ABC transporters are the largest. The number of candidate MDR genes means that study of the drug-resistance properties of an organism cannot be effectively carried out without taking a genomic perspective. RESULTS We have annotated sequences for all 60 ABC transporters from the Caenorhabditis elegans genome, and performed a phylogenetic analysis of these along with the 49 human, 30 yeast, and 57 fly ABC transporters currently available in GenBank. Classification according to a unified nomenclature is presented. Comparison between genomes reveals much gene duplication and loss, and surprisingly little orthology among analogous genes. Proteins capable of conferring MDR are found in several distinct subfamilies and are likely to have arisen independently multiple times. CONCLUSIONS ABC transporter evolution fits a pattern expected from a process termed 'dynamic-coherence'. This is an unusual result for such a highly conserved gene family as this one, present in all domains of cellular life. Mechanistically, this may result from the broad substrate specificity of some ABC proteins, which both reduces selection against gene loss, and leads to the facile sorting of functions among paralogs following gene duplication.
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Affiliation(s)
- Jonathan A Sheps
- British Columbia Cancer Research Centre, BC Cancer Agency, 601 West 10th Avenue, Vancouver BC, V5Z 1L6 Canada
| | - Steven Ralph
- British Columbia Cancer Research Centre, BC Cancer Agency, 601 West 10th Avenue, Vancouver BC, V5Z 1L6 Canada
- Current address: Genome BC and the Departments of Botany and Forest Sciences, University of British Columbia, 6270 University Blvd., Vancouver BC, V6T 1Z4 Canada
| | - Zhongying Zhao
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby BC, V5A 1S6 Canada
| | - David L Baillie
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby BC, V5A 1S6 Canada
| | - Victor Ling
- British Columbia Cancer Research Centre, BC Cancer Agency, 601 West 10th Avenue, Vancouver BC, V5Z 1L6 Canada
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14
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Wilkinson M, Loader SP, Gower DJ, Sheps JA, Cohen BL. Phylogenetic relationships of African caecilians (Amphibia: Gymnophiona): Insights from mitochondrial rRNA gene sequences. AFR J HERPETOL 2003. [DOI: 10.1080/21564574.2003.9635483] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Affiliation(s)
- B L Cohen
- University of Glasgow, Institute of Biomedical and Life Sciences, Division of Molecular Genetics, Pontecorvo Building, 56 Dumbarton Road, Glasgow G11 6NU, Scotland.
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Affiliation(s)
- F Zhang
- British Columbia Cancer Research Center, Vancouver, Canada
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Sheps JA, Cheung I, Ling V. Hemolysin transport in Escherichia coli. Point mutants in HlyB compensate for a deletion in the predicted amphiphilic helix region of the HlyA signal. J Biol Chem 1995; 270:14829-34. [PMID: 7782350 DOI: 10.1074/jbc.270.24.14829] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The alpha-hemolysin transporter of Escherichia coli, a member of the ATP-binding cassette transporter super-family, is responsible for secretion of the 107-kDa protein toxin HlyA across both membranes of the Gram-negative envelope in a single step. Secretion of HlyA is dependent on a signal sequence, which occupies the C-terminal 50-60 amino acids of HlyA. Previously, it was shown that point mutants in the transmembrane domain of the transporter HlyB could partially correct the transport defect caused by a deletion of the C-terminal 29 amino acids of HlyA. These suppressor mutations demonstrated a direct interaction between HlyA and HlyB. They also displayed suppressor effects on a broad spectrum of HlyA signal mutants. In the present study, we selected HlyB alleles that complemented an internal deletion of 29 amino acids in HlyA containing a predicted amphiphilic helix region immediately upstream from the previous deletion. This set of HlyB mutants identifies further sites in HlyB that modulate substrate specificity but display allele-specific effects on a range of HlyA signal mutants. The inability to isolate mutations with effects restricted to either half of the signal sequence suggests that the signal is not recognized in a modular fashion by the transporter but rather functions as an integrated whole. We also report the isolation of the first substrate specificity mutation, which lies within the ATP-binding domain of HlyB. This could support a model in which the region of the ATP-binding cassette between the two Walker consensus motifs involved in ATP binding interacts with either the substrate or the transmembrane domains.
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Affiliation(s)
- J A Sheps
- Division of Molecular and Structural Biology, Ontario Cancer Institute, Toronto, Canada
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Zhang F, Sheps JA, Ling V. Complementation of transport-deficient mutants of Escherichia coli alpha-hemolysin by second-site mutations in the transporter hemolysin B. J Biol Chem 1993; 268:19889-95. [PMID: 8366127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Hemolysin B (HlyB) is a membrane-bound transport protein composed of an amino-terminal multiple membrane-spanning portion followed by a conserved ATP binding sequence. Together with the inner membrane protein HlyD and the outer membrane protein TolC, HlyB is responsible for transport of the 107-kDa toxin HlyA from the cytoplasm, across both membranes of the cell envelope of Escherichia coli, directly to the medium. We have used a mutational approach to investigate a postulated interaction between HlyA and HlyB. We have isolated transport-deficient mutants of HlyA altered in the C-terminal signal sequence and used one of these, a deletion of 29 amino acids, to select compensatory mutants in the transporter protein HlyB. Fifteen mutants located at six different sites, all mapping within the amino-terminal multiple membrane-spanning domain of HlyB, were identified. All of the mutations are clustered into three groups located close to the predicted inner face of the cytoplasmic membrane. We propose that these locations are close to sites on HlyB that interact with the C-terminal signal sequence of HlyA. This interaction is likely to involve either binding of HlyA to HlyB or activation of the transport mechanism. The compensatory mutants also display different patterns of specificity in terms of their ability to transport different HlyA mutants. The fact that point mutations are able to compensate for drastic changes in the signal sequence of HlyA suggests that substrate specificity of transporters such as HlyB may shift dramatically during evolutionary history. This could account for the diversity of substrates observed for the ABC transporter superfamily in nature.
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Affiliation(s)
- F Zhang
- Division of Molecular and Structural Biology, University of Toronto, Ontario, Canada
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