ABCMdb

ABCB11 p.Ile498Thr

Reviews:	p.Ile498Thr D
Predicted by SNAP2:	A: D (75%), C: D (59%), D: D (91%), E: D (85%), F: D (59%), G: D (85%), H: D (85%), K: D (91%), L: D (59%), M: N (87%), N: D (80%), P: D (91%), Q: D (80%), R: D (85%), S: D (80%), T: D (59%), V: N (61%), W: D (85%), Y: D (75%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: D, F: D, G: D, H: D, K: D, L: N, M: N, N: D, P: D, Q: D, R: D, S: D, T: D, V: N, W: D, Y: D,

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[hide] The bile salt export pump. Pflugers Arch. 2007 Feb;453(5):611-20. Epub 2006 Oct 19. Stieger B, Meier Y, Meier PJ
The bile salt export pump.
Pflugers Arch. 2007 Feb;453(5):611-20. Epub 2006 Oct 19., [PMID:17051391]

Abstract [show]
Canalicular secretion of bile salts mediated by the bile salt export pump Bsep constitutes the major driving force for the generation of bile flow. Bsep is a member of the B-family of the super family of ATP-binding cassette transporters and is classified as ABCB11. Bsep has a narrow substrate specificity, which is largely restricted to bile salts. Bsep is extensively regulated at the transcriptional and posttranscriptional level, which directly modulates canalicular bile formation. Pathophysiological alterations of Bsep by either inherited mutations or acquired processes such as inhibition by drugs or disease-related down regulation may lead to a wide spectrum of mild to severe forms of liver disease. Furthermore, many genetic variants of Bsep are known, some of which potentially render individuals susceptible to acquired forms of liver disease.

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160 Their bile flow rate is slightly but not significantly lower in comparison to controls, but the total bile salt output into bile is massively reduced and their liver bile salt concen- S114R G238V V284L* C336S D482G R487H S593R E636G G982R G1004D R1153CD R1268Q E186G E297G R432T I498T I498T T923P A926P R1050C R1128H S194P G260D N519S A1228V V444A K461E M677V R698H PFIC2 BRIC2 acquired cholestasis SNP Fig. 2 Putative secondary structure of Bsep (NT-005403) generated with the TOPO program (http://www.sacs.ucsf.edu/TOPO-run/wtopo.pl). Login to comment

[hide] Prediction of drug-induced intrahepatic cholestasi... Expert Opin Drug Saf. 2007 Jan;6(1):71-86. Sakurai A, Kurata A, Onishi Y, Hirano H, Ishikawa T
Prediction of drug-induced intrahepatic cholestasis: in vitro screening and QSAR analysis of drugs inhibiting the human bile salt export pump.
Expert Opin Drug Saf. 2007 Jan;6(1):71-86., [PMID:17181454]

Abstract [show]
Drug-induced intrahepatic cholestasis is one of the major causes of hepatotoxicity, which often occur during the drug discovery and development process. Human ATP-binding cassette transporter ABCB11 (sister of P-glycoprotein/bile salt export pump) mediates the elimination of cytotoxic bile salts from liver cells to bile, and, therefore, plays a critical role in the generation of bile flow. The authors have recently developed in vitro high-speed screening and quantitative structure-activity relationship analysis methods to investigate the interaction of ABCB11 with a variety of compounds. Based on the extent of inhibition of the bile salt export pump, the authors analysed the quantitative structure-activity relationship to identify chemical groups closely associated with the inhibition of ABCB11. This approach provides a new tool to predict compounds with a potential risk of drug-induced intrahepatic cholestasis.

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120 H2N COOH S56L G238V G260D C336S L339V V444A K461E D482G T923P K930X G982R R1090X R1153C Outside Inside R1268Q A1228VE1186K R1128H R1057X R1050C A926P A865V R698H E636G M677V S593R E592Q N591S R575XA570T Q558H I498T R432T R415Q R299K E297G V284A I206V S194P E186G cholestasis Expert Opin. Drug Saf. (2007) 6(1) Table 1. Login to comment
122 [39,41,44,46,48,102] - 12 1381 A→G Lys461Glu PFIC2 [35] - 13 1445 A→G Asp482Gly PFIC2 [35] - 13 1493 T→C Ile498Thr PFIC2?BRIC2? Login to comment

[hide] Missense mutations and single nucleotide polymorph... Hepatology. 2009 Feb;49(2):553-67. Byrne JA, Strautnieks SS, Ihrke G, Pagani F, Knisely AS, Linton KJ, Mieli-Vergani G, Thompson RJ
Missense mutations and single nucleotide polymorphisms in ABCB11 impair bile salt export pump processing and function or disrupt pre-messenger RNA splicing.
Hepatology. 2009 Feb;49(2):553-67., [PMID:19101985]

Abstract [show]
The gene encoding the human bile salt export pump (BSEP), ABCB11, is mutated in several forms of intrahepatic cholestasis. Here we classified the majority (63) of known ABCB11 missense mutations and 21 single-nucleotide polymorphisms (SNPs) to determine whether they caused abnormal ABCB11 pre-messenger RNA splicing, abnormal processing of BSEP protein, or alterations in BSEP protein function. Using an in vitro minigene system to analyze splicing events, we found reduced wild-type splicing for 20 mutations/SNPs, with normal mRNA levels reduced to 5% or less in eight cases. The common ABCB11 missense mutation encoding D482G enhanced aberrant splicing, whereas the common SNP A1028A promoted exon skipping. Addition of exogenous splicing factors modulated several splicing defects. Of the mutants expressed in vitro in CHO-K1 cells, most appeared to be retained in the endoplasmic reticulum and degraded. A minority had BSEP levels similar to wild-type. The SNP variant A444 had reduced levels of protein compared with V444. Treatment with glycerol and incubation at reduced temperature overcame processing defects for several mutants, including E297G. Taurocholate transport by two assessed mutants, N490D and A570T, was reduced compared with wild-type. Conclusion: This work is a comprehensive analysis of 80% of ABCB11 missense mutations and single-nucleotide polymorphisms at pre-mRNA splicing and protein processing/functional levels. We show that aberrant pre-mRNA splicing occurs in a considerable number of cases, leading to reduced levels of normal mRNA. Thus, primary defects at either the protein or the mRNA level (or both) contribute significantly to BSEP deficiency. These results will help to develop mutation-specific therapies for children and adults suffering from intrahepatic cholestasis due to BSEP deficiency.

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67 ABCB11 Missense Mutations and SNPs Functionally Analyzed in This Study Exon Nucleotide Change Predicted Protein Effect Location in Protein Associated Phenotype Prevalence or Frequency* Any Defect(s) Identified Reference 4 c.149TϾC L50S NH2 term PFIC 1 family (het) Immature protein 31 5 c.270TϾC F90F EC1 SNP 2.7%-7.7% 43, 45 6 c.403GϾA E135K EC1 BRIC 1 family (het) Reduced levels of mature protein † 6 c.409GϾA E137K EC1 BRIC / ICP 1 family (het) Immature protein ‡ 7 c.500CϾT A167V TM2 PFIC 1 family (hom) Mild exon skipping beta 7 c.557AϾG E186G IC1 BRIC 2 families (both het) Moderate exon skipping; greatly reduced levels of mature protein 8, 37 7 c.580TϾC S194P IC1 SNP-PSC 1.1% 43 7 c.593TϾC L198P IC1 BRIC / ICP / DC 1 family (het) Greatly reduced levels of mature protein # 8 c.713GϾT G238V EC2 PFIC 1 family (hom) 29 8 c.725CϾT T242I TM4 PFIC 1 family (het) 31 8 c.779GϾA G260D TM4 SNP-PBC 0.8% 43 9 c.850GϾC V284L IC2 PFIC 1 family (het) No protein 28 9 c.851TϾC V284A IC2 SNP 0.5% Increased levels of mature protein 43, 45† 9 c.889GϾA E297K IC2 Prolonged NNH 1 family (het) Moderate differential splicing; immature protein ‡ 9 c. 890AϾG E297G IC2 PFIC, BRIC PFIC, 45 families (14 hom, 31 het) BRIC, 4 families (2 hom, 2 het) Greatly reduced levels of mature protein 7, 8, 12, 29-32, 35 10 c.936GϾT Q312H IC2 PFIC 1 family (het) ‡ 10 c.937CϾA R313S IC2 PFIC 1 family (het) 31 10 c.957AϾG G319G TM5 SNP 1.5 - 7.5% Mild exon skipping 42, 43, 45 10 c.980GϾA G327E TM5 PFIC 1 family (het) 31 10 c.1007GϾC C336S TM5 PFIC 1 family (het) 29 11 c.1168GϾC A390P NBF PFIC, BRIC 2 families (both het) Immature protein 31; # 12 c.1129GϾA G410D NBF PFIC 1 family (het) 31 12 c.1238TϾG L413W NBF PFIC 1 family (het) Greatly reduced levels of mature protein 31 12 c.1244GϾA R415Q NBF SNP-ICP 1.3% 42 12 c.1295GϾC R432T NBF BRIC 1 family (het) Reduced levels of mature protein 12 13 c.1331CϾT A444V NBF SNP, ICP, CC, DC, BRIC 43-60% Increased levels of mature protein 8, 28, 37, 39-45 13 c.1381AϾG K461E WA PFIC 1 family (hom) Immature protein 7 13 c.1388CϾT T463I WA PFIC 1 family (het) Mild exon skipping 31 13 c.1396CϾA Q466K Adj WA PFIC 1 family (het) 31 13 c.1409GϾA R470Q Adj WA PFIC 2 families (1 het, 1 consanguineous) Immature protein 31 14 c.1442TϾA V481E NBF1 PFIC 1 family (het) 31 14 c.1445AϾG D482G NBF1 PFIC 22 families (16 het, 6 hom) Severe differential splicing; immature protein 7, 30-32 14 c.1468AϾG N490D NBF1 PFIC 1 family (het) Greatly reduced levels of mature protein; reduction in bile salt transport 31 14 c.1493TϾC I498T NBF1 PFIC / BRIC 1 family (het) 38 14 c.1530CϾA T510T NBF1 SNP-PBC 0.7% 43 14 c.1535TϾC I512T NBF1 PFIC 1 family (het) 31 14 c.1544AϾC N515T NBF1 PFIC 1 family (het) 31, 32 14 c.1440GϾA R517H NBF1 PFIC 1 family (het) No protein 31, 32 14 c.1605CϾT A535A NBF1 SNP 0.3% Slightly reduced levels mature protein 39, 45 14 c.1621AϾC I541L NBF1 PFIC 3 families (1 het, 2 consanguineous) No protein 31-33 15 c.1643TϾA F548Y Adj ABCm PFIC 1 family (het) 31, 32 15 c.1685GϾA G562D ABCm PFIC 1 family (het) 31 15 c.1708GϾA A570T Adj ABCm/WB PFIC, BRIC PFIC, 1 family Greatly reduced levels of mature protein; reduction in bile salt transport 8, 31 Table 1. Login to comment
140 Variant BSEP forms found in this study to have the same molecular weight and about the same abundance as the wild-type protein are I498T (c.1493TϾC; Fig. 5A), N1211D (c.3631AϾG), L1242I (c.3724CϾA), E709K (c.2125GϾA; Fig. 5C), , T586I (c.1757CϾT; Fig. 5E), as well as the SNP N591S (c.1772AϾG; Fig. 5F). Login to comment
207 Normal levels of mature BSEP were seen for the predicted missense mutations I498T (c.1493TϾC; Fig. 5A), L1242I (c.3724CϾA; Fig. 5C), and N1211D (c.3631AϾG; Fig. 5C). Login to comment
208 Mutation I498 is located within the first nucleotide binding fold (NBF) between the Walker A and ABC signature motifs, which are domains highly conserved among ABC transporter superfamily members.2 The mutation I498T is associated with the less severe, intermittent BRIC clinical phenotype.38 Intermittent episodes of cholestasis may arise when any functional activity of I498T is compromised within a patient`s liver. Login to comment

[hide] The transporter "variome": the missing link betwee... Hepatology. 2009 Feb;49(2):352-4. Mullenbach R, Lammert F
The transporter "variome": the missing link between gene variants and bile salt transporter function.
Hepatology. 2009 Feb;49(2):352-4., [PMID:19177487]

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33 The resulting changes in protein structure can cause: (1) Functional impairment at the respective site of function (i.e., at the canalicular membrane) without detectable reduction (as seen in ABCB11 p.I498T). Login to comment

[hide] A patient with novel ABCB11 gene mutations with ph... J Hepatol. 2006 Jan;44(1):240-2. Epub 2005 Nov 2. Lam CW, Cheung KM, Tsui MS, Yan MS, Lee CY, Tong SF
A patient with novel ABCB11 gene mutations with phenotypic transition between BRIC2 and PFIC2.
J Hepatol. 2006 Jan;44(1):240-2. Epub 2005 Nov 2., [PMID:16290310]

Abstract [show]
We describe a PFIC2 patient with a good response to ursodeoxycholic acid for 9 years. We found two novel ABCB11 gene mutations in the patient, i.e. I498T and 2098delA. The correlation of the patient's genotypes with the clinical course supports the existence of a phenotypic continuum between BRIC2 and PFIC2.

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1 We found two novel ABCB11 gene mutations in the patient, i.e. I498T and 2098delA. Login to comment
75 ARMS assay for 1493 TOC The ARMS assay was performed in order to determine whether the mutation 1493 TOC (I498T) was a SNP or a missense mutation. Login to comment
76 The mutation was not present in any of the 50 normal, Chinese individuals who were screened by the ARMS assay-implying that I498T is probably a disease-causing mutation (data not shown). Login to comment
78 (Top) The missense mutation 1493 TOC or I498T in the patient shown in the sense direction. Login to comment
87 Based on the negative results of the ARMS assay, the novel mutation I498T (1493 TOC) is believed to be a disease-causing mutation. Login to comment
88 I498T occurs in the first ATP-binding domain of BSEP, but it does not affect the Walker motifs or the linker region of the cytoplasmic domain-implying that the mutation is a BRIC2-specific mutation. Login to comment
89 The I498T mutation resembles other missense mutations that are recently reported and might affect the BSEP molecule in a similar manner [6,7]. Login to comment
90 I498T might produce an immature BSEP molecule that is confined to the endoplasmic reticulumandislaterdegradedbytheproteasomepathway[6]. Login to comment

[hide] The bile salt export pump (BSEP) in health and dis... Clin Res Hepatol Gastroenterol. 2012 Dec;36(6):536-53. doi: 10.1016/j.clinre.2012.06.006. Epub 2012 Jul 12. Kubitz R, Droge C, Stindt J, Weissenberger K, Haussinger D
The bile salt export pump (BSEP) in health and disease.
Clin Res Hepatol Gastroenterol. 2012 Dec;36(6):536-53. doi: 10.1016/j.clinre.2012.06.006. Epub 2012 Jul 12., [PMID:22795478]

Abstract [show]
The bile salt export pump (BSEP) is the major transporter for the secretion of bile acids from hepatocytes into bile in humans. Mutations of BSEP are associated with cholestatic liver diseases of varying severity including progressive familial intrahepatic cholestasis type 2 (PFIC-2), benign recurrent intrahepatic cholestasis type 2 (BRIC-2) and genetic polymorphisms are linked to intrahepatic cholestasis of pregnancy (ICP) and drug-induced liver injury (DILI). Detailed analysis of these diseases has considerably increased our knowledge about physiology and pathophysiology of bile secretion in humans. This review focuses on expression, localization, and function, short- and long-term regulation of BSEP as well as diseases association and treatment options for BSEP-associated diseases.

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185 PFIC BRIC/NFC ICP Other liver diseases Genetic variants without disease association Missense mutations M1V C336S D549V L1055P E135K E137K T87R V43I S701P G19R W342G G556R C1083Y E137K L198P M123T S56L L712L L50S A382G G562D A1110E E186G E297G S194P Q121K A865D M62K R387H A570T S1114R L198P R415Q L198P R128H A865G C68Y A390P L581F G1116E E297G V444A G260D I206V S874P C107R G410D A588V G1116F G374S D482G E297K V284A I939M I112T L413W S593R G1116R A390P N591S V444A G295C R958Q W114R I420T I627T S1120N R432T T655I T510T G295R F959C Y157C D440E E636G R1128C V444A T655I G295S F959V A167T G455E R698C S1144R I498T D676Y R299K T965S A167V K461E S699P R1153C A570T P710P R303K F971L I182K T463I E709K R1153H T586I L827I L339V F971Y M183T Q466K G758R S1154P G648V G855R H423R L1006F M183V R470Q G766R N1173D T655I E1186K V444A N1009H G188W Y472C Y818F T1210P T923P V444D K1145N M217R V481E R832C N1211D A926P V444G I1183T R223C D482G R832H V1212F R948C A459V S226L R487H T859R R1231Q G1004D I468I G238V R487P A865V R1231W R1050C R487L T242I N490D Q869P L1242I G1116R Q546K A257G I498T G877R D1243G R1128H Q558H V284L G499E S901R R1268Q L1197G E592Q E297G I512T R948C A1283V R1231Q V597M R303G N515T N979D G1292V R616G R303K R517H G982R G1298R T619A Q312H F540L G1004D M677L R313S I541L T1029K M677V G327E I541T G1032R R696Q W330R F548Y A1044P R698H Nonsense mutations (premature stop-codons) S25X Y472X Y772X R1090X E96X W493X Q791X V1147X W330X R520X R928X Q1215X Y354X I528X Y1041X R1235X R415X R575X R1057X E1302X R470X Q702X Q1058X Table 1 (Continued) PFIC BRIC/NFC ICP Other liver diseases Genetic variants without disease association Splice site mutations 76 + 3G > T 908 + 1delG 2178 + 1G > T 3057-2A > G Q159Q 77-1G > C 908 + 1G > T 2179-2A > G 3213 + 1delG Q361Q 99-1G > T 908 + 1G > A 2343 + 1G > T 3213 + 4A > G 150 + 3A > C 1435-13 -8del 2343 + 2T > C 3213 + 5G > A 390-1G > A 2012-8T > G 2611-2A > T 611 + 1G > A 2178 + 1G > A R1001R Deletions/insertions/frame shifts Q101Dfs8X L380Wfs18X G648Vfs5X Q1058Hfs38X F959Hfs1X T127Hfs6X A382 A388del K700Sfs12X I1061Vfs34X F959Gfs48X N199Ifs14X P456Pfs24X T919del L1165del L232Cfs9X H484Rfs5X K930Efs92X A1192Efs50X R303Sfs17X I528Sfs21X K930Efs79X T1256Tfs40X V368Rfs27X I610Qfs45X K969 K972del Synonymous variants without disease association R33R F90F L232L I416I G557G I876I A1028A K1145K D36D I134I Y269Y G418G V597V G937G K1070K R52R S136S Q312Q F427F A804A Y981Y T1086T D58D V195V G319G E395E A535A G817G G1004G A1110A The overview shows ࣈ 290 known variants of BSEP on the protein level, except splice site mutations, which are shown on cDNA level. Login to comment
197 be a transition between BRIC-2 and PFIC-2 as shown for a patient compound heterozygous for p.I498T and c.2098delA [143] or siblings with the homozygous mutation p.G374S. Login to comment

[hide] Hypothyroidism Associated with ATP8B1 Deficiency. J Pediatr. 2015 Dec;167(6):1334-1339.e1. doi: 10.1016/j.jpeds.2015.08.037. Epub 2015 Sep 15. Li L, Deheragoda M, Lu Y, Gong J, Wang J
Hypothyroidism Associated with ATP8B1 Deficiency.
J Pediatr. 2015 Dec;167(6):1334-1339.e1. doi: 10.1016/j.jpeds.2015.08.037. Epub 2015 Sep 15., [PMID:26382629]

Abstract [show]
OBJECTIVE: To examine whether hypothyroidism is an extrahepatic feature of ATPase, aminophospholipid transporter, class I, type 8B, member 1 (ATP8B1) deficiency. STUDY DESIGN: Children with normal gamma-glutamyltransferase cholestasis (n = 47; 13 patients with ATP8B1 deficiency, 19 with ATP-binding cassette, subfamily B (MDR/TAP), member 11 (ABCB11) deficiency, and 15 without either ATP8B1 or ABCB11 mutations) were enrolled. Clinical information and thyroid function test results were retrospectively retrieved from clinical records and compared. Hypothyroidism was diagnosed by clinical-biochemistry criteria (thyroid function test results). RESULTS: Three out of 13 patients with ATP8B1 deficiency were diagnosed as hypothyroid and 2 as subclinically hypothyroid. The frequency of hypothyroidism and subclinical hypothyroidism was significantly higher than in patients with ABCB11 deficiency (5/13 vs 0/19, P = .006) and in patients without ATP8B1 or ABCB11 mutations (5/13 vs 0/15, P = .013). Thyroid function test results normalized after hormone replacement in all 5 patients, with no relief of cholestasis. CONCLUSIONS: As hypothyroidism can be another extrahepatic feature of ATP8B1 deficiency, thyroid function should be monitored in these patients.

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71 ABCB11 mutations and immunostaining in patients with ABCB11 mutations Patient ID Sex Nucleotide change Amino acid change Mutation origin BSEP expression GGT expression 244 Female c.145C>T/- p.Q49X/- Paternal/- Absent Normal 653 Female c.1197+1G>T/c.1197+1G>T -/- Paternal/maternal Not assessed Not assessed 727 Male c.2782C>T/c.3593A>G p.R928X/p.H1198R Maternal/paternal Not assessed Not assessed 889 Female c.3457C>T/c.3623A>G p.R1153C/p.Y1208C Paternal/maternal Absent Normal 919 Female c.1493T>C/c.1493T>C p.I498T/p.I498T Paternal/maternal Not assessed Not assessed 996 Male c.612-2_4 CTA>TT/- -/- Maternal/- Absent Normal 1022 Male c.212T>A/c.677C>T p.L71H/p.S226L Paternal/maternal Absent Normal 1131 Male c.409G>A/c.2216delC p.E137K/p.P740QfsX6 De novo/paternal Absent Normal 1134 Male c.1760C>G/c.3677G>C p.S587X/p.R1226P Maternal/paternal Absent Absent 1139 Female c.2935A>G/c.3746T>G p.N979D/p.L1249X Not assessed Not assessed Not assessed 1140 Male c.542G>T/c.1370_1372dupGTG p.R181I/p.V458dup Maternal/paternal Not assessed Not assessed 1219 Female c.872T>C/c.3691C>T p.V291A/p.R1231W Maternal/paternal Not assessed Not assessed 334* Female c.2944G>A/- p.G982R/- Not assessed Normal Normal 802* Female c.3458G>A/- p.R1153H/- Not assessed Not assessed Not assessed 862* Male c.634G>A/c.849A>C/c.1638G>T p.A212T/p.E283D/p.Q546H Maternal/maternal/de novo Not assessed Not assessed 864* Male c.1727A>G/- p.N576S/- Paternal/- Normal Normal 1165* Male c.1583T>C/c.1583T>C p.I528T/p.I528T Not assessed Not assessed Not assessed 1167* Male c.334A>G/c.3233T>C p.I112V/p.I1078T Not assessed Not assessed Not assessed 1242* Male c.2783G>A/- p.R928Q/- Not assessed Not assessed Not assessed Bold: Novel mutation. Login to comment