ABCB4 p.Ala546Asp
ClinVar: |
c.1637C>A
,
p.Ala546Asp
D
, Pathogenic
|
Predicted by SNAP2: | C: N (53%), D: D (75%), E: D (75%), F: D (75%), G: D (59%), H: D (66%), I: D (66%), K: D (75%), L: D (71%), M: N (57%), N: D (66%), P: D (75%), Q: D (63%), R: D (71%), S: N (66%), T: N (66%), V: D (53%), W: D (80%), Y: D (75%), |
Predicted by PROVEAN: | C: D, D: D, E: D, F: D, G: D, H: D, I: D, K: D, L: D, M: D, N: D, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: D, |
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[hide] Heterozygous MDR3 missense mutation associated wit... Hum Mol Genet. 2000 May 1;9(8):1209-17. Dixon PH, Weerasekera N, Linton KJ, Donaldson O, Chambers J, Egginton E, Weaver J, Nelson-Piercy C, de Swiet M, Warnes G, Elias E, Higgins CF, Johnston DG, McCarthy MI, Williamson C
Heterozygous MDR3 missense mutation associated with intrahepatic cholestasis of pregnancy: evidence for a defect in protein trafficking.
Hum Mol Genet. 2000 May 1;9(8):1209-17., 2000-05-01 [PMID:10767346]
Abstract [show]
Intrahepatic cholestasis of pregnancy (ICP) is a liver disease of pregnancy with serious consequences for the mother and fetus. Two pedigrees have been reported with ICP in the mothers of children with a subtype of autosomal recessive progressive familial intrahepatic cholestasis (PFIC) with raised serum gamma-glutamyl transpeptidase (gamma-GT). Affected children have homozygous mutations in the MDR3 gene (also called ABCB4 ), and heterozygous mothers have ICP. More frequently, however, ICP occurs in women with no known family history of PFIC and the genetic basis of this disorder is unknown. We investigated eight women with ICP and raised serum gamma-GT, but with no known family history of PFIC. DNA sequence analysis revealed a C to A transversion in codon 546 in exon 14 of MDR3 in one patient, which results in the missense substitution of the wild-type alanine with an aspartic acid. We performed functional studies of this mutation introduced into MDR1, a closely related homologue of MDR3. Fluorescence activated cell sorting (FACS) and western analysis indicated that this missense mutation causes disruption of protein trafficking with a subsequent lack of functional protein at the cell surface. The demonstration of a heterozygous missense mutation in the MDR3 gene in a patient with ICP with no known family history of PFIC, analysed by functional studies, is a novel finding. This shows that MDR3 mutations are responsible for the additional phenotype of ICP in a subgroup of women with raised gamma-GT.
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No. Sentence Comment
44 In addition to the normal cytosine at this position, an adenine was also detected; this results in the substitution of the wild-type alanine with a mutant aspartic acid (A546D).
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ABCB4 p.Ala546Asp 10767346:44:170
status: NEW69 We therefore introduced the equivalent A546D mutation into the first NBD of P-gp1 and studied the functional consequences of the change in transiently transfected mammalian cells.
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ABCB4 p.Ala546Asp 10767346:69:39
status: NEW94 Evidence that A544D-P-gp1 is a trafficking mutant The finding that substitution of an aspartic acid for an alanine in a highly conserved region of NBD1 did not alter the ability of the mature protein to transport R123 was unexpected and suggested that the equivalent A546D-MDR3 protein mutant would also be functional.
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ABCB4 p.Ala546Asp 10767346:94:267
status: NEW127 When considered together, these results demonstrate that not all of the mature protein is at the cell surface. These results show that the MDR3 mutation A546D causes abnormal protein glycosylation and trafficking when its equivalent is expressed in P-gp1.
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ABCB4 p.Ala546Asp 10767346:127:153
status: NEW128 DISCUSSION Our analysis of the sequence of the coding region of the MDR3 gene in eight patients with ICP and raised γ-GT has revealed the presence of a mutation in exon 14 (A546D) in one individual.
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ABCB4 p.Ala546Asp 10767346:128:179
status: NEW135 The occurrence of the A546D mutation, the substitution of a hydrophobic amino acid with a charged polar amino acid, in the highly conserved first NBD, suggested that this mutation would also result in loss-of-function of the MDR3 protein.
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ABCB4 p.Ala546Asp 10767346:135:22
status: NEW136 In order to gain insight into the functional consequences of this mutation, we tested the effects of the equivalent mutation to A546D in P-gp1 (A544D).
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ABCB4 p.Ala546Asp 10767346:136:128
status: NEW147 The A546D mutation in the MDR3 protein is likely to have a similar phenotype as there is considerable sequence identity between the proteins in this domain (87%), and because the NBDs of P-gp1 and the MDR3 protein have been shown to be functionally interchangeable (27).
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ABCB4 p.Ala546Asp 10767346:147:4
status: NEW199 Study of the MDR3 protein A546D mutation in P-gp1 Plasmid pMDR-wt encodes wild-type P-gp1 with a hexa-histidine tag at the C-terminus and has been described previously (28).
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ABCB4 p.Ala546Asp 10767346:199:26
status: NEW203 Site-directed mutagenesis Alignment of the amino acid sequence of human P-gp1 with the MDR3 protein identified A544 as the P-gp1 equivalent of MDR3 protein A546. Site-directed mutagenesis was used to alter codon 544 of MDR1 to encode an aspartic acid, adopting the C→A tranversion of the second position of the codon analogous to the A546D mutant of the MDR3 protein.
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ABCB4 p.Ala546Asp 10767346:203:341
status: NEW[hide] A missense mutation in ABCB4 gene involved in prog... Hepatology. 2009 Apr;49(4):1218-27. Delaunay JL, Durand-Schneider AM, Delautier D, Rada A, Gautherot J, Jacquemin E, Ait-Slimane T, Maurice M
A missense mutation in ABCB4 gene involved in progressive familial intrahepatic cholestasis type 3 leads to a folding defect that can be rescued by low temperature.
Hepatology. 2009 Apr;49(4):1218-27., [PMID:19185004]
Abstract [show]
Progressive familial intrahepatic cholestasis type 3 (PFIC3) is a rare liver disease characterized by early onset of cholestasis that leads to cirrhosis and liver failure before adulthood. PFIC3 may be improved by chronic administration of ursodeoxycholic acid, although in many cases liver transplantation is the only therapy. The disease is caused by mutations of the adenosine triphosphate (ATP)-binding cassette, sub-family B, member 4 (ABCB4) [multidrug resistance 3 (MDR3)] gene encoding a specific hepatocellular canalicular transporter involved in biliary phosphatidylcholine secretion. Several mutations have been reported; however, the effect of individual mutations has not been investigated. ABCB4 is highly homologous to ATP-binding cassette, sub-family B, member 1 (ABCB1) (MDR1), the multidrug transporter responsible for drug resistance of cancer cells. We have studied the effect of mutation I541F localized to the first nucleotide-binding domain, which is highly conserved between ABCB4 and ABCB1. Plasmids encoding the wild-type human ABCB4 or rat ABCB1-green fluorescing protein (GFP) construct, and corresponding I541F-mutants, were expressed in hepatocellular carcinoma, human (HepG2) and Madin-Darby canine kidney (MDCK) cells. Expression studies showed that ABCB4 was localized at the bile canalicular membrane in HepG2 cells and at the apical surface in MDCK cells, whereas the I541F mutant was intracellular. In MDCK cells, ABCB1-I541F also accumulated intracellularly in compartments, which were identified as the endoplasmic reticulum and cis-Golgi, and remained partially endoH-sensitive. After shifting cells to 27 degrees C, ABCB1-I541F was expressed at the apical cell surface in a mature and active form. Similarly, ABCB4 was significantly trafficked to the membrane of bile canaliculi in HepG2 cells. CONCLUSION: Mutation I541F causes mislocalization of both ABCB4 and ABCB1. Intracellular retention of ABCB4-I541F can explain the disease in PFIC3 patients bearing this mutation. The observation that plasma membrane expression and activity can be rescued by low temperature opens perspectives to develop novel therapies for the treatment of PFIC3.
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No. Sentence Comment
229 Dixon et al.26 have shown that the A546D mutation described in a patient with intrahepatic cholestasis of pregnancy affected the traffic of an ABCB1 mutant to the plasma membrane, but not its activity.
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ABCB4 p.Ala546Asp 19185004:229:35
status: NEW230 In the work of Dixon et al.,26 ABCB1 was used as a model to reproduce the A546D ABCB4 mutation.
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ABCB4 p.Ala546Asp 19185004:230:74
status: NEW[hide] Function and pathophysiological importance of ABCB... Pflugers Arch. 2007 Feb;453(5):601-10. Epub 2006 Apr 19. Oude Elferink RP, Paulusma CC
Function and pathophysiological importance of ABCB4 (MDR3 P-glycoprotein).
Pflugers Arch. 2007 Feb;453(5):601-10. Epub 2006 Apr 19., [PMID:16622704]
Abstract [show]
Like several other ATP-binding cassette (ABC) transporters, ABCB4 is a lipid translocator. It translocates phosphatidylcholine (PC) from the inner to the outer leaflet of the canalicular membrane of the hepatocyte. Its function is quite crucial as evidenced by a severe liver disease, progressive familial intrahepatic cholestasis type 3, which develops in persons with ABCB4 deficiency. Translocation of PC makes the phospholipid available for extraction into the canalicular lumen by bile salts. The primary function of biliary phospholipid excretion is to protect the membranes of cells facing the biliary tree against these bile salts: the uptake of PC in bile salt micelles reduces the detergent activity of these micelles. In this review, we will discuss the functional aspects of ABCB4 and the regulation of its expression. Furthermore, we will describe the clinical and biochemical consequences of complete and partial deficiency of ABCB4 function.
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No. Sentence Comment
141 Canalicular lipid transport defects can cause gallstone formation Cholesterol supersaturation of bile, which occurs in a large proportion of humans, leads to the formation of cholesterol Walker B; L556R 571del Truncation PFIC3 LPAC ICP 27 splice Truncation 132 del Truncation TM 2; W138R TM 12; 981 del Truncation Linker; Q636X Truncation TM 11; R957X Truncation TM 6; S346I E395G Walker B; I541F TM 12; G983S Walker A; V425M Walker A; T424A Walker B; D564G TM 7; F711S 180 del truncation 336 delT truncation Exon 22-23 del truncation F165I T175A TM 5; M301T TM 5; S320F 336 insT truncation Walker A; 432 insA truncation E528D L591Q W658stop 757 insT R788E A934T P1161S TM 5; S320F TM 8; G762ER144X Walker B; A546D Walker B; G535AALL 96 del Truncation Walker B; L556R 571del Truncation PFIC3 LPAC ICP 27 splice Truncation 132 del Truncation TM 2; W138R TM 12; 981 del Truncation Linker; Q636X Truncation TM 11; R957X Truncation TM 6; S346I E395G Walker B; I541F TM 12; G983S Walker A; V425M Walker A; T424A Walker B; D564G TM 7; F711S 180 del truncation 336 delT truncation Exon 22-23 del truncation F165I T175A TM 5; M301T TM 5; S320F 336 insT truncation Walker A; 432 insA truncation E528D L591Q W658stop 757 insT R788E A934T P1161S TM 5; S320F TM 8; G762ER144X Walker B; A546D Walker B; G535AALL 96 del Truncation Fig. 3 Summary of the known mutations and their localization in the protein, as identified in patients with PFIC type 3, LPAC syndrome (intrahepatic gallstone formation), and intrahepatic cholestasis of pregnancy (ICP).
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ABCB4 p.Ala546Asp 16622704:141:709
status: NEWX
ABCB4 p.Ala546Asp 16622704:141:1274
status: NEW[hide] Intrahepatic cholestasis of pregnancy: three novel... Aliment Pharmacol Ther. 2006 Jun 1;23(11):1649-53. Floreani A, Carderi I, Paternoster D, Soardo G, Azzaroli F, Esposito W, Variola A, Tommasi AM, Marchesoni D, Braghin C, Mazzella G
Intrahepatic cholestasis of pregnancy: three novel MDR3 gene mutations.
Aliment Pharmacol Ther. 2006 Jun 1;23(11):1649-53., [PMID:16696816]
Abstract [show]
BACKGROUND: The aetiology of intrahepatic cholestasis of pregnancy is unknown, but more than 10 different MDR3 gene mutations have recently been identified. AIM: To evaluate the genetic contribution of the MDR3 gene in the pathogenesis of intrahepatic cholestasis of pregnancy in Italian subjects. METHODS: We performed a multicentre prospective case-control study, enrolling 80 women with intrahepatic cholestasis of pregnancy at the third trimester of pregnancy and 80 pregnant women without intrahepatic cholestasis of pregnancy. Genomic DNA was extracted from peripheral venous blood leucocytes using standard procedures. The polymerase chain reaction was used to amplify exon 14 of the MDR3 gene and the polymerase chain reaction products were sequenced using a Big Dye Terminator Cycle Sequencing kit. RESULTS: Three novel non-synonymous heterozygous mutations in exon 14 were found (4%; E528D, R549H, G536R) among the 80 intrahepatic cholestasis of pregnancy patients, whereas the pregnant controls were all negative for exon 14 polymorphisms. The three patients involved had normal GGT and bilirubin, but high levels of both ALT and serum bile acids. One had cholesterol bile stones. The outcome of pregnancy was normal for two (with vaginal delivery), while foetal distress was recorded in the third. CONCLUSIONS: These three novel mutations add further information on the involvement of the MDR3 gene in intrahepatic cholestasis of pregnancy. As in other studies, we found only heterozygous mutations that could cause an impaired transport protein function, not its absence (which is responsible for more severe liver disease). Different genetic backgrounds might justify the presence of novel MDR3 gene mutations.
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No. Sentence Comment
35 MDR3 mutations reported in the literature Mutation (codon) Exon Reference (R144X) 6 Gendrot et al.5 481G>A (R150K) 6 Mu¨llenbach et al.6 426-432del (132) 6 DeVree et al.13 959C>T (S320F) 9 Rosmordurc et al.,14 Pauli-Magnus et al.9 (G535D) 14 Lucena et al.7 1669 C>A (A546D) 14 Dixon et al.4 1712 del T (571) 14 Jacquemin et al.8, 15 2285 G>A (G762E) 18 Pauli-Magnus et al.9 2901 C>T (R957X) 23 DeVree et al.13 conditions included an initial denaturation step at 94 °C for 5 min, followed by 40 cycles of denaturation at 94 °C for 30 s, annealing at 55 °C for 30 s and extension at 72 °C for 30 s.
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ABCB4 p.Ala546Asp 16696816:35:272
status: NEW[hide] Functional hot spots in human ATP-binding cassette... Protein Sci. 2010 Nov;19(11):2110-21. Kelly L, Fukushima H, Karchin R, Gow JM, Chinn LW, Pieper U, Segal MR, Kroetz DL, Sali A
Functional hot spots in human ATP-binding cassette transporter nucleotide binding domains.
Protein Sci. 2010 Nov;19(11):2110-21., [PMID:20799350]
Abstract [show]
The human ATP-binding cassette (ABC) transporter superfamily consists of 48 integral membrane proteins that couple the action of ATP binding and hydrolysis to the transport of diverse substrates across cellular membranes. Defects in 18 transporters have been implicated in human disease. In hundreds of cases, disease phenotypes and defects in function can be traced to nonsynonymous single nucleotide polymorphisms (nsSNPs). The functional impact of the majority of ABC transporter nsSNPs has yet to be experimentally characterized. Here, we combine experimental mutational studies with sequence and structural analysis to describe the impact of nsSNPs in human ABC transporters. First, the disease associations of 39 nsSNPs in 10 transporters were rationalized by identifying two conserved loops and a small alpha-helical region that may be involved in interdomain communication necessary for transport of substrates. Second, an approach to discriminate between disease-associated and neutral nsSNPs was developed and tailored to this superfamily. Finally, the functional impact of 40 unannotated nsSNPs in seven ABC transporters identified in 247 ethnically diverse individuals studied by the Pharmacogenetics of Membrane Transporters consortium was predicted. Three predictions were experimentally tested using human embryonic kidney epithelial (HEK) 293 cells stably transfected with the reference multidrug resistance transporter 4 and its variants to examine functional differences in transport of the antiviral drug, tenofovir. The experimental results confirmed two predictions. Our analysis provides a structural and evolutionary framework for rationalizing and predicting the functional effects of nsSNPs in this clinically important membrane transporter superfamily.
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No. Sentence Comment
50 Disease-associated nsSNPs at Three Structural Hotspots in Human ABC Transporter NBDs Gene Disease Position ARA motif ABCB11 BRIC2 A570T ABCD1 X-ALD A616V CFTR CF A559T ABCC6 PXE R765Q ABCC8 HHF1 R841G ABCC8 HHF1 R1493Q ABCC8 HHF1 R1493W ABCD1 X-ALD R617C ABCD1 X-ALD R617G ABCD1 X-ALD R617H CFTR CF R560K CFTR CF R560S CFTR CF R560T ABCA1 HDLD1 A1046D ABCB4 ICP A546D C-loop 1 motif ABCC8 HHF1 D1471H ABCC8 HHF1 D1471N CFTR CBAVD G544V ABCC8 HHF1 G1478R C-loop2 motif ABCA4 STGD1 H2128R ABCC8 HHF1 K889T ABCD1 X-ALD R660P ABCD1 X-ALD R660W ABCA1 HDLD2 M1091T ABCA4 STGD1 E2131K ABCA12 LI2 E1539K ABCA4 STGD1 and CORD3 E1122K CFTR CF L610S ABCC8 HHF1 L1543P ABCA1 Colorectal cancer sample; somatic mutation A2109T ABCC9 CMD1O A1513T ABCD1 X-ALD H667D CFTR CF A613T ABCA1 HDLD2 D1099Y ABCD1 X-ALD T668I CFTR CF D614G ABCA4 STGD1 R2139W ABCA4 STGD1 R1129C ABCA4 ARMD2, STGD1, and FFM R1129L Disease abbreviations are as follows: BRIC2, benign recurrent intrahepatic cholestasis type 2; X-ALD, X-linked adrenoleukodystrophy; CF, cystic fibrosis; PXE, Pseudoxanthoma elasticum; HHF1, familial hyperinsulinemic hypoglycemia-1; HDLD1, high density lipoprotein deficiency type 1; ICP, intrahepatic cholestasis of pregnancy; CBAVD, congenital bilateral absence of the vas deferens; STGD1, Stargardt disease type 1; HDLD2, high density lipoprotein deficiency type 2; LI2, ichthyosis lamellar type 2; CORD3, cone-rod dystrophy type 3; CMD1O, cardiomyopathy dilated type 1O; ARMD2, age-related macular degeneration type 2; FFM, fundus flavimaculatus.
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ABCB4 p.Ala546Asp 20799350:50:362
status: NEW[hide] Role of multidrug resistance 3 deficiency in pedia... Semin Liver Dis. 2001 Nov;21(4):551-62. Jacquemin E
Role of multidrug resistance 3 deficiency in pediatric and adult liver disease: one gene for three diseases.
Semin Liver Dis. 2001 Nov;21(4):551-62., [PMID:11745043]
Abstract [show]
Class III multidrug resistance P-glycoproteins, mdr2 in mice and MDR3 in humans, are canalicular phospholipid translocators involved in biliary phospholipid (phosphatidylcholine) excretion. The role of an MDR3 gene defect in liver disease was initially suspected in a subtype of progressive familial intrahepatic cholestasis called PFIC3. Several MDR3 mutations have been identified in children with PFIC3 and are associated with a low level of phospholipids in bile, leading to a high biliary cholesterol saturation index. Mutations leading to a truncated protein are associated with an absence of canalicular MDR3 protein. The phenotypic spectrum of PFIC3 ranges from neonatal cholestasis to cirrhosis in young adults. There is now strong evidence that in addition to PFIC3, an MDR3 defect can be involved in intrahepatic cholestasis of pregnancy and in cholesterol gallstone disease. Therefore, at least three human liver diseases are due to a single gene deficiency. Patients with PFIC3 due to MDR3 deficiency may benefit from ursodeoxycholic acid therapy and could be good candidates for cell therapy in the future.
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No. Sentence Comment
113 Reference 37 Patient 1 No A546D Defect of trafficking 50 First WalkerB motif PFIC3, progressive familial intrahepatic cholestasis type 3; MDR3, multidrug resistance 3; ICP, intrahepatic cholestasis of pregnancy; GGT, gamma-glutamyltransferase (N, normal value is from reference 45); AA, amino acid; TMD, transmembrane domain; *, personal data (E. Jacquemin).
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ABCB4 p.Ala546Asp 11745043:113:26
status: NEW[hide] ABCB4: Insights from pathobiology into therapy. Clin Res Hepatol Gastroenterol. 2014 Oct;38(5):557-63. doi: 10.1016/j.clinre.2014.03.001. Epub 2014 Jun 19. Falguieres T, Ait-Slimane T, Housset C, Maurice M
ABCB4: Insights from pathobiology into therapy.
Clin Res Hepatol Gastroenterol. 2014 Oct;38(5):557-63. doi: 10.1016/j.clinre.2014.03.001. Epub 2014 Jun 19., [PMID:24953525]
Abstract [show]
Adenosine triphosphate (ATP)-binding cassette, sub-family B, member 4 (ABCB4), also called multidrug resistance 3 (MDR3), is a member of the ATP-binding cassette transporter superfamily, which is localized at the canalicular membrane of hepatocytes, and mediates the translocation of phosphatidylcholine into bile. Phosphatidylcholine secretion is crucial to ensure solubilization of cholesterol into mixed micelles and to prevent bile acid toxicity towards hepatobiliary epithelia. Genetic defects of ABCB4 may cause progressive familial intrahepatic cholestasis type 3 (PFIC3), a rare autosomic recessive disease occurring early in childhood that may be lethal in the absence of liver transplantation, and other cholestatic or cholelithiasic diseases in heterozygous adults. Development of therapies for these conditions requires understanding of the biology of this transporter and how gene variations may cause disease. This review focuses on our current knowledge on the regulation of ABCB4 expression, trafficking and function, and presents recent advances in fundamental research with promising therapeutic perspectives.
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No. Sentence Comment
104 The A546D mutation was shown to affect ABCB4 traffic [58].
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ABCB4 p.Ala546Asp 24953525:104:4
status: NEW