ABCMdb

ABCB11 p.Ala570Thr

Reviews:	p.Ala570Thr D
Predicted by SNAP2:	C: D (66%), D: D (85%), E: D (85%), F: D (85%), G: D (75%), H: D (80%), I: D (80%), K: D (85%), L: D (85%), M: D (75%), N: D (80%), P: D (85%), Q: D (80%), R: D (80%), S: D (59%), T: D (63%), V: D (80%), W: D (85%), Y: D (85%),
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] 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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123 [40] rs1156869 14 1674 G→C Gln558His - [102] - 14 1708 G→A Ala570Thr BRIC2 [45] - 14 1723 C→T Arg575X PFIC2 [35,46,47] rs11568367 15 1772 A→G Asn591Ser ICP [39,102] rs11568370 15 1774 G→C Glu592Gln - [102] - 15 1779 T→A/G Ser593Arg PFIC2? Login to comment

[hide] Levels of plasma membrane expression in progressiv... Am J Physiol Cell Physiol. 2007 Nov;293(5):C1709-16. Epub 2007 Sep 13. Lam P, Pearson CL, Soroka CJ, Xu S, Mennone A, Boyer JL
Levels of plasma membrane expression in progressive and benign mutations of the bile salt export pump (Bsep/Abcb11) correlate with severity of cholestatic diseases.
Am J Physiol Cell Physiol. 2007 Nov;293(5):C1709-16. Epub 2007 Sep 13., [PMID:17855769]

Abstract [show]
Human BSEP (ABCB11) mutations are the molecular basis for at least three clinical forms of liver disease, progressive familial intrahepatic cholestasis type 2 (PFIC2), benign recurrent intrahepatic cholestasis type 2 (BRIC2), and intrahepatic cholestasis of pregnancy (ICP). To better understand the pathobiology of these disease phenotypes, we hypothesized that different mutations may cause significant differences in protein defects. Therefore we compared the effect of two PFIC2 mutations (D482G, E297G) with two BRIC2 mutations (A570T and R1050C) and one ICP mutation (N591S) with regard to the subcellular localization, maturation, and function of the rat Bsep protein. Bile salt transport was retained in all but the E297G mutant. Mutant proteins were expressed at reduced levels on the plasma membrane of transfected HEK293 cells compared with wild-type (WT) Bsep in the following order: WT > N591S > R1050C approximately A570T approximately E297G >> D482G. Total cell protein and surface protein expression were reduced to the same extent, suggesting that trafficking of these mutants to the plasma membrane is not impaired. All Bsep mutants accumulate in perinuclear aggresome-like structures in the presence of the proteasome inhibitor MG-132, suggesting that mutations are associated with protein instability and ubiquitin-dependent degradation. Reduced temperature, sodium butyrate, and sodium 4-phenylbutyrate enhanced the expression of the mature and cell surface D482G protein in HEK293 cells. These results suggest that the clinical phenotypes of PFIC2, BRIC2, and ICP may directly correlate with the amount of mature protein that is expressed at the cell surface and that strategies to stabilize cell surface mutant protein may be therapeutic.

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9 Therefore we compared the effect of two PFIC2 mutations (D482G, E297G) with two BRIC2 mutations (A570T and R1050C) and one ICP mutation (N591S) with regard to the subcellular localization, maturation, and function of the rat Bsep protein. Login to comment
11 Mutant proteins were expressed at reduced levels on the plasma membrane of transfected HEK293 cells compared with wild-type (WT) Bsep in the following order: WT Ͼ N591S Ͼ R1050C ϳ A570T ϳ E297G ϾϾ D482G. Login to comment
45 All point mutations (D482G, E297G, A570T, R1050C, N591S) were introduced with the QuickChange Site-Directed Mutagenesis Kit (Stratagene, La Jolla, CA). Login to comment
64 PFIC2 (D482G, E297G), BRIC2 (A570T, R1050C), and ICP (N591S) mutations that are investigated in this study are indicated in italics. Login to comment
94 Sf9 cells infected with recombinant virus (mock, WT, D482G, E297G, A570T, R1050C, and N591S) were harvested, and cell membranes were prepared as described previously (23). Login to comment
107 The subcellular distributions of D482G, E297G, A570T, R1050C, and N591S were examined first because intracellular accumulation of misfolded proteins has been shown for many diseases. Login to comment
118 The level of cell surface expression of Bsep protein was quantitated by densitometry and determined to be in the following order: WT (100%) Ͼ N591S (75.6 Ϯ 15.6%) Ͼ E297G (38.5 Ϯ 12.6%) ϳ R1050C (35.6 Ϯ 14.5%) ϳ A570T (29.5 Ϯ 8.8%) ϾϾ D482G (5.7 Ϯ 2.3%). Login to comment
120 The total expression (cell surface and intracellular proteins) also showed changes similar to those in cell surface expression: WT (100%) Ͼ N591S (73.5 Ϯ 4.3%) Ͼ E297G (33.7 Ϯ 20.4%) ϳ R1050C (26.7 Ϯ 16.0%) ϳ A570T (11.9 Ϯ 5.2%) ϾϾ D482G (2.5 Ϯ 2.0%) (Fig. 4B). Login to comment
150 The membrane vesicles expressing D482G, A570T, R1050C, or N591S showed similar levels of taurocholate uptake compared with WT Bsep. Login to comment
155 Cells were transiently transfected with pEGFPN1 (control), rat Bsep-GFP [wild type (WT)], D482G-GFP, E297G-GFP, A570T-GFP, R1050C-GFP, and N591S-GFP constructs. Login to comment
164 A PFIC2 mutation (D482G) is highly unstable (ϳ5% of WT), while the BRIC2 variants A570T and R1050C are expressed at the plasma membrane at intermediate levels (ϳ25% of WT). Login to comment
169 Cells were transfected with rat Bsep-GFP (WT), D482G-GFP, E297G-GFP, A570T-GFP, R1050C-GFP, and N591S-GFP constructs and were examined for GFP by confocal laser microscopy. Login to comment
171 D482G, E297G, A570T, and R1050C mutants partially colocalized with recycling endosome marker Rab11. Login to comment
176 D4, D482G; E2, E297G; A5, A570T; R10, R1050C; N5, N591S. Login to comment
183 P Ͻ 0.05, D482G, E297G, A570T, R1050C, and N591S compared with WT control. Login to comment
229 A: immunoblot of the isolated Sf9 cell membrane proteins with anti-Bsep polyclonal antibody: GFP control expressed in HEK293 cells, WT expressed in HEK293 cells, rat liver homogenate (L), pFastBac1-Gus control (C), wild type (WT), D482G (D4), E297G (E2), A570T (A5), R1050C (R10), N591S (N5). Login to comment
231 B: TCA (200 ␮M) stimulates and orthovanadate inhibits ATPase activity in membrane vesicles containing comparable levels of WT or D482G, E297G, A570T, R1050C, and N591S mutant Bsep. Login to comment

[hide] Phenotypic differences in PFIC2 and BRIC2 correlat... Am J Physiol Gastrointest Liver Physiol. 2008 Jan;294(1):G58-67. Epub 2007 Oct 18. Kagawa T, Watanabe N, Mochizuki K, Numari A, Ikeno Y, Itoh J, Tanaka H, Arias IM, Mine T
Phenotypic differences in PFIC2 and BRIC2 correlate with protein stability of mutant Bsep and impaired taurocholate secretion in MDCK II cells.
Am J Physiol Gastrointest Liver Physiol. 2008 Jan;294(1):G58-67. Epub 2007 Oct 18., [PMID:17947449]

Abstract [show]
Progressive familial cholestasis (PFIC) 2 and benign recurrent intrahepatic cholestasis (BRIC) 2 are caused by mutations in the bile salt export pump (BSEP, ABCB11) gene; however, their prognosis differs. PFIC2 progresses to cirrhosis and requires liver transplantation, whereas BRIC2 is clinically benign. To identify the molecular mechanism(s) responsible for the phenotypic differences, eight PFIC2 and two BRIC2 mutations were introduced in rat Bsep, which was transfected in MDCK II cells. Taurocholate transport activity, protein expression, and subcellular distribution of these mutant proteins were studied in a polarized MDCK II monolayer. The taurocholate transport activity was approximately half of the wild-type (WT) in BRIC2 mutants (A570T and R1050C), was substantially less in two PFIC2 mutants (D482G and E297G), and was almost abolished in six other PFIC2 mutants (K461E, G982R, R1153C, R1268Q, 3767-3768insC, and R1057X). Bsep protein expression levels correlated closely with transport activity, except for R1057X. The half-life of the D482G mutant was shorter than that of the WT (1.35 h vs. 3.49 h in the mature form). BRIC2 mutants and three PFIC mutants (D482G, E297G, and R1057X) were predominantly distributed in the apical membrane. The other PFIC2 mutants remained intracellular. The R1057X mutant protein was stably expressed and trafficked to the apical membrane, suggesting that the COOH-terminal tail is required for transport activity but not for correct targeting. In conclusion, taurocholate transport function was impaired in proportion to rapid degradation of Bsep protein in the mutants, which were aligned in the following order: A570T and R1050C > D482G > E297G > K461E, G982R, R1153C, R1268Q, 3767-3768insC, and R1057X. These results may explain the phenotypic difference between BRIC2 and PFIC2.

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13 The taurocholate transport activity was approximately half of the wild-type (WT) in BRIC2 mutants (A570T and R1050C), was substantially less in two PFIC2 mutants (D482G and E297G), and was almost abolished in six other PFIC2 mutants (K461E, G982R, R1153C, R1268Q, 3767-3768insC, and R1057X). Login to comment
19 In conclusion, taurocholate transport function was impaired in proportion to rapid degradation of Bsep protein in the mutants, which were aligned in the following order: A570T and R1050C Ͼ D482G Ͼ E297G Ͼ K461E, G982R, R1153C, R1268Q, 3767-3768insC, and R1057X. Login to comment
139 The positions of 8 PFIC2 mutations (E297G, K461E, D482G, G982R, R1057C, R1153C, 3767-3768insC, and R1268Q) and 2 BRIC2 mutations (A570T and R1050C) are indicated by ଝ and ଙ, respectively. Login to comment
166 In contrast, two BRIC2 mutants exhibited considerable transport activity (A570T: 52.2 Ϯ 13.0%, R1050C: 58.7 Ϯ 9.9% of the WT). Login to comment
170 A570T and R1050C Fig. 2. Login to comment
181 mRNA expression levels examined in MDCK II cells expressing these mutants except for A570T were slightly higher than those with WT, but the difference was not statistically significant (Fig. 6D). Login to comment
184 Subcellular distribution study revealed that E297G, R1057X, A570T, and R1050C mutants were predominantly located along the apical membrane, whereas the other PFIC2 mutants (K461E, G982R, R1153C, R1268Q, and 3767-3768insC) remained intracellular (Fig. 7). Login to comment
185 In summary, BRIC2 mutants (A570T and R1050C) were expressed substantially, trafficked correctly, and maintained half of transport activity. Login to comment
286 TC transport activity was 50-60% in BRIC2 mutants (A570T and R1050C) and 0-30% in PFIC2 mutants. Login to comment
290 From the view of maintenance of TC transport activity, the mutants could be aligned in the following order: A570T and R1050C Ͼ D482G Ͼ E297G Ͼ K461E, G982R, R1153C, R1268Q, 3767-3768insC, and R1057X. Login to comment

[hide] Update on progressive familial intrahepatic choles... J Pediatr Gastroenterol Nutr. 2008 Mar;46(3):241-52. Alissa FT, Jaffe R, Shneider BL
Update on progressive familial intrahepatic cholestasis.
J Pediatr Gastroenterol Nutr. 2008 Mar;46(3):241-52., [PMID:18376240]

Abstract [show]
Three distinct forms of familial intrahepatic cholestasis are the result of mutations in the ATP8B1, ABCB11, and ABCB4 genes. The pathophysiologies of the latter 2 of these diseases are well characterized and are the result of abnormalities in canalicular excretion of bile acids and phospholipids, respectively. The molecular pathophysiology of the systemic disease associated with mutations in ATP8B1 remains unclear. In all of these diseases, wide variations in clinical phenotypes have been observed. The variability can be ascribed at least in part to predicted genotype:phenotype correlations. Disease- and genotype-specific prognoses and therapeutic approaches may exist, although much more information needs to be ascertained before clinicians can confidently make decisions based on genetic information.

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194 Even more subtle mutations of ABCB11 were described in patients with an intermittent form of disease (BRIC2; see below), these mutations include E186G, A570T, T923P, A926P, R1050C, R1128H, V444A, and E297G. 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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8 Taurocholate transport by two assessed mutants, N490D and A570T, was reduced compared with wild-type. Login to comment
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
142 The mutations N490D (c.1468AϾG; Fig. 5A), R1128H (c.3383GϾA; Fig. 5B), E297G (c. 890AϾG), and A570T (c.1708GϾA; Fig. 5D), and E186G (c.557AϾG; Fig. 5E) resulted in significantly reduced levels of mature protein, and the L198P (c.593TϾC) variant was barely detectable (Fig. 5C). Login to comment
154 The following mutations showed an enrichment of mature BSEP: R1153H (c.3458GϾA; Fig. 6B), R1128C (c.3382CϾT), R1128H (c.3383GϾA), R1231Q (c.3692GϾA), R1050C (c.3148CϾT; Fig. 6C) and R1268Q (c.3892GϾA), A570T (c.1708GϾA), and E297K (c.889GϾA; Fig. 6D). Login to comment
163 Wild-type and variant ABCB11 baculoviruses with the mutations N490D (c.1468AϾG) and A570T (c.1708GϾA) were created, and, after infection of Hi5 insect cells, inside-out membrane vesicles were prepared to perform taurocholate transport assays.3 The mutant N490D was chosen because it generated a mature form of BSEP, although in reduced abundance (Fig. 5A), and because the associated disease was severe,30 whereas A570T was amenable to glycerol and reduced temperature: these enhanced the abundance of a mature form of BSEP (Fig. 6D). Login to comment
167 The N490D mutation was associated with 27% and the A570T mutation with 60% of normal activity. Login to comment
174 (A) Baculoviruses were created that contained either the wild-type ABCB11 cDNA, that encoding N490D (c.1468AϾG), or A570T (c.1708GϾA) and were used, along with a mock baculovirus, to transduce Hi5 insect cells. Login to comment
219 These include the PFIC-associated mutations E297G (c.890AϾG; Fig. 6A), R1128C (c.3382CϾT) and R1231Q (c.3692GϾA; Fig. 6C), and R1268Q (c.3892GϾA; Fig. 6.d), the BRIC-associated mutations R1128H (c.3383GϾA) and R1050C (c.3148CϾT; Fig. 6C), and E297K (c.889GϾA; Fig. 6D), as well as A570T (c.1708GϾA), which can be associated with either form of disease. Login to comment
226 Two mutations, N490D (c.1468AϾG) and A570T (c.1708GϾA), were expressed in insect cells and then assessed for their ability to transport taurocholate (Fig. 7A, B). Login to comment
228 Despite equal expression of both mutants in these cells, N490D had only 27% and A570T had 60% of the activity of the wild-type protein, respectively. Login to comment
230 A570T was identified on both alleles in a patient with BRIC who required a partial external biliary diversion to treat progressive cholestasis at the age of 18 years.8 Both N490D and A570T are situated in the first NBF of BSEP; N490D is conserved across the MDR family, whereas A570T is also conserved in MDR-associated protein 2 and CFTR. Login to comment
231 However, the substitution N490D is more functionally detrimental and apparently more clinically severe than A570T. Login to comment
232 The recent expression of rat Bsep with A570T in MDCK cells gave comparable results to our study with respect to levels of mature protein.14 These authors attributed an approximately 50% reduction of taurocholate transport solely to reduced BSEP protein expression levels, whereas our data suggest an additional defect in transport activity. Login to comment

[hide] Morphologic findings in progressive familial intra... Am J Surg Pathol. 2011 May;35(5):687-96. Evason K, Bove KE, Finegold MJ, Knisely AS, Rhee S, Rosenthal P, Miethke AG, Karpen SJ, Ferrell LD, Kim GE
Morphologic findings in progressive familial intrahepatic cholestasis 2 (PFIC2): correlation with genetic and immunohistochemical studies.
Am J Surg Pathol. 2011 May;35(5):687-96., [PMID:21490445]

Abstract [show]
Progressive familial intrahepatic cholestasis, type 2 (PFIC2), characterized by cholestasis in infancy that may progress to cirrhosis, is caused by mutation in ABCB11, which encodes bile salt export pump (BSEP). We correlated histopathologic, immunohistochemical, and ultrastructural features in PFIC2 with specific mutations and clinical course. Twelve patients with clinical PFIC2 and ABCB11 mutations were identified, and 22 liver biopsy and explant specimens were assessed. All had hepatocellular cholestasis; most had canalicular bile plugs. At least 1 specimen from every patient had centrizonal/sinusoidal fibrosis, often with periportal fibrosis. Neonatal hepatitis-like features (inflammation, giant cells, necrosis) varied. In 2 of the 5 patients with paired specimens obtained >6 months apart, lobular and portal fibrosis worsened. Transmission electron microscopy (EM) in all 9 patients studied showed canalicular dilatation, microvilli loss, abnormal mitochondrial internal structure, and varying intracanalicular accumulation of finely granular bile. Canalicular staining for BSEP was absent in 10 patients and present in 2 patients, 1 of whom had intermittent symptoms. ABCB11 sequencing of all patients identified 6 novel and 10 previously described mutations, with nonsense, missense, and/or noncoding mutations in the 10 patients without immunohistochemically demonstrable BSEP. Missense and/or noncoding mutations were identified in the 2 patients with demonstrable BSEP, whose clinical course was more indolent. Mutations ending ABCB11 transcription appear linked, through hepatocellular necrosis and fibrosis, to worse outcome. In conclusion, light microscopy and electron microscopy findings in clinical PFIC2 can support diagnosis, but are variable and nonspecific. Therefore, no correlation between specific mutations and histopathology is yet possible.

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143 Immunohistochemical Findings and Genetic Abnormalities Patient BSEP Mutation Type of Mutation(s) 1 Absent c.890A>G (p.E297G)* Missense5,7,10,13,16,19,20 2 Absent c.1723C>T (p.R575X) Nonsense7,19,20 c.2178+1G>T Noncoding region20 3 Present c.1708G>A (p.A570T) Missense20 c.3634G>T (p.V1212F) Missense, predicted deleterious 4 Absent c.3164T>C (p.L1055P)* Missense, predicted deleterious 5 Absent c.3692G>A (p.R1231Q) Missense20 c.2296G>A (p.G766R) Missense20 6 Absent c.2782C>T (p.R928X) Nonsense13 c.3268C>T (p.R1090X) Nonsense5,7,13 7 Present c.3347G>A (p.G1116E) Missense, predicted deleterious IVS 23-8 G-A Noncoding region 8 Absent IVS 16-8 T>Gw Noncoding region10 9 Absent c.2944G>A (p.G982R) Missense5,7,19,20 c.2296G>A (p.G766R) Missense20 10 Absent c.2944G>A (p.G982R) Missense5,7,19,20 c.2296G>A (p.G766R) Missense20 11 Absent c.319T>C (p.C107R) Missense, predicted deleterious c.611+4A>G Noncoding region 12 Absent c.1723C>T (p.R575X) Nonsense7,19,20 c.2178+1G>T Noncoding region20 *Homozygous. Login to comment

[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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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. Login to comment

[hide] Severe bile salt export pump deficiency: 82 differ... Gastroenterology. 2008 Apr;134(4):1203-14. doi: 10.1053/j.gastro.2008.01.038. Epub 2008 Jan 18. Strautnieks SS, Byrne JA, Pawlikowska L, Cebecauerova D, Rayner A, Dutton L, Meier Y, Antoniou A, Stieger B, Arnell H, Ozcay F, Al-Hussaini HF, Bassas AF, Verkade HJ, Fischler B, Nemeth A, Kotalova R, Shneider BL, Cielecka-Kuszyk J, McClean P, Whitington PF, Sokal E, Jirsa M, Wali SH, Jankowska I, Pawlowska J, Mieli-Vergani G, Knisely AS, Bull LN, Thompson RJ
Severe bile salt export pump deficiency: 82 different ABCB11 mutations in 109 families.
Gastroenterology. 2008 Apr;134(4):1203-14. doi: 10.1053/j.gastro.2008.01.038. Epub 2008 Jan 18., [PMID:18395098]

Abstract [show]
BACKGROUND & AIMS: Patients with severe bile salt export pump (BSEP) deficiency present as infants with progressive cholestatic liver disease. We characterized mutations of ABCB11 (encoding BSEP) in such patients and correlated genotypes with residual protein detection and risk of malignancy. METHODS: Patients with intrahepatic cholestasis suggestive of BSEP deficiency were investigated by single-strand conformation polymorphism analysis and sequencing of ABCB11. Genotypes sorted by likely phenotypic severity were correlated with data on BSEP immunohistochemistry and clinical outcome. RESULTS: Eighty-two different mutations (52 novel) were identified in 109 families (9 nonsense mutations, 10 small insertions and deletions, 15 splice-site changes, 3 whole-gene deletions, 45 missense changes). In 7 families, only a single heterozygous mutation was identified despite complete sequence analysis. Thirty-two percent of mutations occurred in >1 family, with E297G and/or D482G present in 58% of European families (52/89). On immunohistochemical analysis (88 patients), 93% had abnormal or absent BSEP staining. Expression varied most for E297G and D482G, with some BSEP detected in 45% of patients (19/42) with these mutations. Hepatocellular carcinoma or cholangiocarcinoma developed in 15% of patients (19/128). Two protein-truncating mutations conferred particular risk; 38% (8/21) of such patients developed malignancy versus 10% (11/107) with potentially less severe genotypes (relative risk, 3.7 [confidence limits, 1.7-8.1; P = .003]). CONCLUSIONS: With this study, >100 ABCB11 mutations are now identified. Immunohistochemically detectable BSEP is typically absent, or much reduced, in severe disease. BSEP deficiency confers risk of hepatobiliary malignancy. Close surveillance of BSEP-deficient patients retaining their native liver, particularly those carrying 2 null mutations, is essential.

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150 Missense Mutations in ABCB11 Nucleotide change Predicted effect Exon CpG site Location Change in: Size Charge Hyd/Pol Shape c.149Tb0e;C p.Leu50Ser 4 No NH2 term Y Y Y c.470Ab0e;G p.Tyr157Cys 6 No TM2 Y Y Y c.725Cb0e;T p.Thr242Ile 8 No TM4 Y Y c.890Ab0e;G p.Glu297Gly 9 No IC2 Y Y Y c.908Gb0e;A p.Arg303Lys 9 No IC2 c.937Cb0e;A p.Arg313Ser 10 Yes IC2 Y Y Y Y c.980Gb0e;A p.Gly327Glu 10 No TM5 Y Y Y c.1168Gb0e;C p.Ala390Pro 11 No TM/NBF Y c.1229Gb0e;A p.Gly410Asp 12 No TM/NBF Y Y c.1238Tb0e;G p.Leu413Trp 12 No TM/NBF c.1388Cb0e;T p.Thr463Ile 13 No Adj Walker A Y Y Y c.1396Cb0e;A p.Gln466Lys 13 No Adj Walker A Y c.1409Gb0e;A p.Arg470Gln 13 Yes Adj Walker A Y c.1415Ab0e;G p.Tyr472Cys 13 No Adj Walker A Y Y Y c.1442Tb0e;A p.Val481Glu 14 No NBF1 Y Y Y c.1445Ab0e;G p.Asp482Gly 14 No NBF1 Y Y c.1460Gb0e;C p.Arg487Pro 14 Yes NBF1 Y Y Y Y c.1468Ab0e;G p.Asn490Asp 14 No NBF1 Y c.1535Tb0e;C p.Ile512Thr 14 No NBF1 Y Y Y c.1544Ab0e;C p.Asn515Thr 14 No NBF1 Y Y c.1550Gb0e;A p.Arg517His 14 Yes NBF1 Y Y c.1621Ab0e;C p.Ile541Leu 14 No NBF1 c.1622Tb0e;C p.Ile541Thr 14 No NBF1 Y Y Y c.1643Tb0e;A p.Phe548Tyr 15 No Adj ABC c.1685Gb0e;A p.Gly562Asp 15 No ABC Y Y c.1708Gb0e;A p.Ala570Thr 15 Yes ABC/Walker B Y c.1763Cb0e;T p.Ala588Val 15 No Adj Walker B Y c.2272Gb0e;C p.Gly758Arg 19 No NBF/TM Y Y Y c.2296Gb0e;A p.Gly766Arg 19 Yes TM7 Y Y Y c.2494Cb0e;T p.Arg832Cys 21 Yes IC3 Y Y Y Y c.2576Cb0e;G p.Thr859Arg 21 No IC3 Y Y Y Y c.2842Cb0e;T p.Arg948Cys 23 Yes IC4 Y Y Y Y c.2935Ab0e;G p.Asn979Asp 23 No TM11 Y c.2944Gb0e;A p.Gly982Arg 23 Yes TM11 Y Y Y c.3086Cb0e;A p.Thr1029Lys 24 No TM12 Y Y Y Y c.3329Cb0e;A p.Ala1110Glu 25 Yes Adj Walker A Y Y Y c.3382Cb0e;T p.Arg1128Cys 25 Yes Adj Walker A Y Y Y Y c.3457Cb0e;T p.Arg1153Cys 26 Yes NBF2 Y Y Y Y c.3458Gb0e;A p.Arg1153His 26 Yes NBF2 Y Y c.3460Tb0e;C p.Ser1154Pro 26 No NBF2 Y c.3628Ab0e;C p.Thr1210Pro 27 No Adj ABC Y c.3691Cb0e;T p.Arg1231Trp 27 Yes ABC/Walker B Y Y c.3692Gb0e;A p.Arg1231Gln 27 Yes ABC/Walker B Y c.3724Cb0e;A p.Leu1242Ile 27 No Walker B c.3892Gb0e;A p.Gly1298Arg 28 No NBF2 Y Y Y NOTE. Login to comment
222 BSEP deficiency represents a phenotypic continuum between progressive early-onset1 disease and remitting, and late-onset, phenotypes.3-7 Eleven different mutations have been reported in BSEP deficiency disease clinically assessed as intermediate6 or mild in severity.4,5,7 Three of these, E297G, A570T, and c.2178af9;1Gb0e;A, have also been found in progressive familial intrahepatic cholestasis. 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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182 Mutations such as p.E186G, p.E297G, p.R432T, p.A570T, p.T923P, p.A926P, p.G1004D, p.R1050C and p.R1128H have been described in BRIC-2 patients [137,140-142] (Table 1). Login to comment
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

[hide] Biosynthesis and trafficking of the bile salt expo... Mol Aspects Med. 2014 Jun;37:3-14. doi: 10.1016/j.mam.2013.05.001. Epub 2013 May 15. Soroka CJ, Boyer JL
Biosynthesis and trafficking of the bile salt export pump, BSEP: therapeutic implications of BSEP mutations.
Mol Aspects Med. 2014 Jun;37:3-14. doi: 10.1016/j.mam.2013.05.001. Epub 2013 May 15., [PMID:23685087]

Abstract [show]
The bile salt export pump (BSEP, ABCB11) is the primary transporter of bile acids from the hepatocyte to the biliary system. This rate-limiting step in bile formation is essential to the formation of bile salt dependent bile flow, the enterohepatic circulation of bile acids, and the digestion of dietary fats. Mutations in BSEP are associated with cholestatic diseases such as progressive familial intrahepatic cholestasis type 2 (PFIC2), benign recurrent intrahepatic cholestasis type 2 (BRIC2), drug-induced cholestasis, and intrahepatic cholestasis of pregnancy. Development of clinical therapies for these conditions necessitates a clear understanding of the cell biology of biosynthesis, trafficking, and transcriptional and translational regulation of BSEP. This chapter will focus on the molecular and cell biological aspects of this critical hepatic membrane transporter.

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145 We examined differences in protein maturation, plasma membrane localization and transport activity in mutants of rat Bsep representing two PFIC2 (D482G and E297G), two BRIC2 (A570T and R1050C) and one ICP (N591) mutation (Lam et al., 2007). Login to comment

[hide] Ursodeoxycholic acid stabilizes the bile salt expo... J Gastroenterol. 2014 May;49(5):890-9. doi: 10.1007/s00535-013-0833-y. Epub 2013 May 31. Kagawa T, Orii R, Hirose S, Arase Y, Shiraishi K, Mizutani A, Tsukamoto H, Mine T
Ursodeoxycholic acid stabilizes the bile salt export pump in the apical membrane in MDCK II cells.
J Gastroenterol. 2014 May;49(5):890-9. doi: 10.1007/s00535-013-0833-y. Epub 2013 May 31., [PMID:23722250]

Abstract [show]
BACKGROUND: Ursodeoxycholic acid (UDCA) partly exerts choleretic effects by modifying the function of the bile salt export pump (Bsep, ABCB11). UDCA induces insertion of Bsep into the canalicular membrane of hepatocytes; however, underlying mechanisms remain unknown. We aimed to elucidate molecular mechanisms behind UDCA-induced Bsep activation. METHODS: We established MDCK II cells stably expressing both Bsep and Na(+)-taurocholate cotransporting polypeptide, and investigated the effect of UDCA on activity and protein expression of Bsep using these cells. We performed inhibitor study to know the molecules involved in UDCA-induced Bsep activation, and also tested the influence of UDCA on Bsep having a disease-associated mutation. RESULTS: UDCA activated Bsep in a dose-dependent manner. UDCA did not affect Bsep protein expression in whole cell lysates but increased its apical surface expression by extending the half-life from 2.4 to 5.0 h. This effect was specific to Bsep because UDCA did not affect other apical and basolateral proteins, and was independent of protein kinase A, adenylate cyclase, p38(MAPK), phosphatidylinositide 3-kinase, Ca(2+), and microtubules. NorUDCA activated Bsep similar to UDCA; however, cholic acid, taurocholic acid, and tauroUDCA had no effect. UDCA significantly increased the activity of Bsep with a benign recurrent intrahepatic cholestasis 2 mutation (A570T) but did not affect Bsep with a progressive familial intrahepatic cholestasis 2 mutation (G982R or D482G). CONCLUSIONS: We demonstrated that UDCA stabilizes Bsep protein in the apical membrane and increases its activity in MDCK II cells, presumably by retarding the endocytotic process.

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11 UDCA significantly increased the activity of Bsep with a benign recurrent intrahepatic cholestasis 2 mutation (A570T) but did not affect Bsep with a progressive familial intrahepatic cholestasis 2 mutation (G982R or D482G). Login to comment
88 MDCK-Ntcp cells were transfected with an expression vector that contained mutated Bsep, including any of a PFIC2 mutation (G982R or D482G) and a BRIC2 mutation (A570T) [11]. Login to comment
90 Basal Bsep activity was slightly lower in the A570T mutant (80.6 % of the wild-type Bsep activity) and much lower in the G982R (15.3 %) and D482G (18.8 %) mutants compared with that in wild-type Bsep (Fig. 6). Login to comment
91 UDCA activated the A570T mutant by 1.3-fold. Login to comment
163 The inability of TUDCA to stimulate Bsep activity was unexpected because this molecule has been reported to 0 50 100 150 200 wild-type A570T G982R D482G UDCA - + - + - + - + * ** Bsep activity (%) Fig. 6 The effect of UDCA on mutant Bsep activity. Login to comment
164 MDCK II cells stably expressing wild-type or mutant (A570T, G982R, or D482G) Bsep were incubated in the presence or absence of UDCA (100 lM) for 24 h after preincubation with sodium butyrate (5 mM) for 24 h. Thereafter, these cells were incubated for 1 h at 37 &#b0;C with [3 H]-TC (1 lM) and cold TC (10 lM) in the lower compartment. The intracellular accumulation and transcellular flux of TC were calculated on the basis of the radioactivity in the total cells and apical medium, respectively. Bsep activity was determined by the permeability-surface area product for TC transport across the apical membrane (PSapical), which was calculated as (rate of transcellular TC flux)/(intracellular TC concentration). Login to comment
176 In contrast, the A570T mutant, which causes BRIC2, showed considerable Bsep activity (*70 %), in agreement with a previous report [11]. Login to comment

[hide] Genetic variations of bile salt transporters. Drug Discov Today Technol. 2014 Jun;12:e55-67. doi: 10.1016/j.ddtec.2014.03.006. Kubitz R, Droge C, Kluge S, Stindt J, Haussinger D
Genetic variations of bile salt transporters.
Drug Discov Today Technol. 2014 Jun;12:e55-67. doi: 10.1016/j.ddtec.2014.03.006., [PMID:25027376]

Abstract [show]
Bile salt transporters directly or indirectly influence biological processes through physicochemical or signalling properties of bile salts. The coordinated action of uptake and efflux transporters in polarized epithelial cells of the liver, biliary tree, small intestine and kidney determine bile salt concentrations in different compartments of the body. Genetic variations of bile salt transporters lead to clinical relevant phenotypes of varying severity ranging from a predisposition for drug-induced liver injury to rapidly progressing end-stage liver disease. This review focuses on the impact of genetic variations of bile salt transporters including BSEP, NTCP, ASBT and OSTalpha/beta and discusses approaches for transporter analysis.

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100 For example, the two 'BRIC-2 mutations` p.A570T and p.R1050C had lower expression levels than the 'ICP mutation` p.N591S, but higher expression levels as compared to the PFIC-2 mutations p.D482G and p.E297G [59]. Login to comment
137 BSEP/Bsep NTCP ASBT Exon skipping E186G G1116R G319G R1128C T463I R1128H A926P E1186K A1028Aa R1231W A1110E Aberrant splicing E297K R1153H R832C S1154P S1144R No splice product T586I R1231Q Reduced plasma membrane expression E135K A570T I223T E297Gb N591Sb V444A R1050C Intracellular retention Y818F G982R Reduced or absent bile salt transport A570T R432T A64T K314E V98Ic M264V I206V Q558H I223T C144Y P290S E297Gb N591Sb S267F L243P G374S E1186K I279T T262M a A1028A induces significant exon skipping in vitro but probably not in vivo (unpublished data; Dro &#a8;ge, Ha &#a8;ussinger, Kubitz). Login to comment