ABCMdb

ABCG5 p.Asn437Lys

Predicted by SNAP2:	A: D (85%), C: D (85%), D: D (95%), E: D (95%), F: D (95%), G: D (91%), H: D (95%), I: D (95%), K: D (95%), L: D (95%), M: D (95%), P: D (95%), Q: D (91%), R: D (95%), S: D (91%), T: D (91%), V: D (95%), W: D (95%), Y: D (95%),
Predicted by PROVEAN:	A: D, C: D, D: N, E: D, F: D, G: D, H: D, I: D, K: D, L: D, M: D, P: D, Q: D, R: D, S: N, T: D, V: D, W: D, Y: D,

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[hide] Mutations in ATP-cassette binding proteins G5 (ABC... Hum Mutat. 2001 Oct;18(4):359-60. Hubacek JA, Berge KE, Cohen JC, Hobbs HH
Mutations in ATP-cassette binding proteins G5 (ABCG5) and G8 (ABCG8) causing sitosterolemia.
Hum Mutat. 2001 Oct;18(4):359-60., [PMID:11668628]

Abstract [show]
Sitosterolemia is an autosomal recessive disorder caused by mutations in two adjacent genes encoding coordinately regulated ATP binding cassette (ABC) half transporters (ABCG5 and ABCG8). In this paper we describe three novel mutations causing sitosterolemia: 1) a frameshift mutation (c.336-337insA) in ABCG5 that results in premature termination of the protein at amino acid 197; 2) a missense mutation that changes a conserved residue c.1311C>G; N437K) in ABCG5 and 3) a splice site mutation in ABCG8 (IVS1-2A>G). This study expands the spectrum of the ABCG5 and ABCG8 mutations that cause sitosterolemia. Nine nonsynonymous polymorphisms are also reported: I523V, C600Y, Q604E, and M622V in ABCG5; and D19H, Y54C, T400K, A632V, and Y641F in ABCG8.

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No. Sentence Comment
4 In this paper we describe three novel mutations causing sitosterolemia: 1) a frameshift mutation (c.336-337insA) in ABCG5 that results in premature termination of the protein at amino acid 197; 2) a missense mutation that changes a conserved residue c.1311C>G; N437K) in ABCG5 and 3) a splice site mutation in ABCG8 (IVS1-2A>G). Login to comment
31 A cytosine to guanine substitution was found in exon 9 of ABCG5, which resulted in the substitution of lysine for asparagine at amino acid 437. Login to comment
58 The second mutation results in the substitution of a basic amino acid for an uncharged amino acid (N437K) in a putative transmembrane domain. Login to comment

[hide] Mutations in the human ATP-binding cassette transp... Hum Mutat. 2002 Aug;20(2):151. Heimerl S, Langmann T, Moehle C, Mauerer R, Dean M, Beil FU, von Bergmann K, Schmitz G
Mutations in the human ATP-binding cassette transporters ABCG5 and ABCG8 in sitosterolemia.
Hum Mutat. 2002 Aug;20(2):151., [PMID:12124998]

Abstract [show]
Phytosterolemia or Sitosterolemia is a rare autosomal recessive disorder characterized by highly elevated plasma levels of plant sterols and cholesterol as a consequence of hyperabsorption and impaired biliary secretion of sterols. The disease is caused by mutations in two half size ATP-binding cassette transporters, ABCG5 and ABCG8. We have analyzed the genomic sequence of ABCG5 and ABCG8 in five well-characterized patients with Sitosterolemia. In the first patient we found a heterozygous mutation in exon 8 of the ABCG5 gene leading to a premature termination of the protein (Arg408Ter). This German patient is the first European showing a mutation of the ABCG5 gene. In a second patient we found a novel heterozygous mutation in exon 5 of ABCG8 (c.584T>A; Leu195Gln). Both patients were heterozygous for the identified mutation, but no mutation could be identified on the other chromosome. In three further analyzed patients we found mutations in exons 7, 9 and 11 of the ABCG8 gene, respectively, of which two result in a premature termination signal for translation products. One of these patients was compound heterozygous (Trp361Ter and Arg412Ter), the other was homozygous for Trp361Ter. The third patient was homozygous for an amino acid exchange (Gly574Arg). In conclusion this report describes one novel mutation affecting a highly conserved amino acid and two previously identified mutations in the ABCG8 gene. In addition, we identified for the first time a mutation in the ABCG5 gene of a European Sitosterolemia patient.

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No. Sentence Comment
77 C Y658stop R121stop R164stop Q172stop R184H L195Q P231T G574R G574E L572P L596R N ABC B S AA R263Q E146Q R405H R543S W536stop R412stop W361stop C R419P R419H R408stop R398H N437K R550S R243stop N ABCG5 ABCG8 S B A IVS1 -2A>G Del547C>191stop L501P L596R 1568_1572delTCTTT 1798_1800delTTC Del Exon 3 C336-337insA 201 * Signature 250 ABCG1 Q..EKDEG.R REMVKEILTA L GLLSCANTR TGS.... .LS GGQR KRLAIA ABCG2 ATTMTNHE.K NERINRVIEE L GLDKVADSK VGTQFIR GVS GGER KRTSIG ABCG4 S..EKQEV.K KELVTEILTA L GLMSCSHTR TAL.... .LS GGQR KRLAIA ABCG5 R..RGNPGSF QKKVEAVMAE L SLSHVADRL IGNYSLG GIS TGER RRVSIA ABCG8 PRTFSQAQ.R DKRVEDVIAE L RLRQCADTR VGNMYVR GLS GGER RRVSIG Figure 2: Alignment of the human ABC transporters G1, G2, G4, G5 and G8. The amino acid change Leu195Gln in ABCG8 found in patient 2 is located intracellularly between the Walker A and the Signature C-motif. Login to comment

[hide] Missense mutations in ABCG5 and ABCG8 disrupt hete... J Biol Chem. 2004 Jun 4;279(23):24881-8. Epub 2004 Mar 30. Graf GA, Cohen JC, Hobbs HH
Missense mutations in ABCG5 and ABCG8 disrupt heterodimerization and trafficking.
J Biol Chem. 2004 Jun 4;279(23):24881-8. Epub 2004 Mar 30., 2004-06-04 [PMID:15054092]

Abstract [show]
Mutations in ABCG5 (G5) or ABCG8 (G8) cause sitosterolemia, an autosomal recessive disease characterized by sterol accumulation and premature atherosclerosis. G5 and G8 are ATP-binding cassette (ABC) half-transporters that must heterodimerize to move to the apical surface of cells. We examined the role of N-linked glycans in the formation of the G5/G8 heterodimer to gain insight into the determinants of folding and trafficking of these proteins. Site-directed mutagenesis revealed that two asparagine residues (Asn(585) and Asn(592)) are glycosylated in G5 and that G8 has a single N-linked glycan attached to Asn(619). N-Linked glycosylation of G8 was required for efficient trafficking of the G5/G8 heterodimer, but mutations that abolished glycosylation of G5 did not prevent trafficking of the heterodimer. Both G5 and G8 are bound by the lectin chaperone, calnexin, suggesting that the calnexin cycle may facilitate folding of the G5/G8 heterodimer. To determine the effects of 13 disease-causing missense mutations in G5 and G8 on formation and trafficking of the G5/G8 heterodimer, mutant forms of the half-transporters were expressed in CHO-K1 cells. All 13 mutations reduced trafficking of the G5/G8 heterodimer from the endoplasmic reticulum to the Golgi complex, and most prevented the formation of stable heterodimers between G5 and G8. We conclude that the majority of the molecular defects in G5 and G8 that cause sitosterolemia impair transport of the sterol transporter to the cell surface.

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No. Sentence Comment
203 No mature G5 was present in cells expressing G5 with the R389H, R419H, or N437K mutations. Login to comment
221 These analyses were performed using a trafficking-defective mutant of G5, N437K. Login to comment
247 When the trafficking-defective mutant of G5 (N437K) was coexpressed with G8, the pattern of G5 was virtually identical to that obtained when G5 was expressed alone, indicating that the presence of G8 had no effect on the size or on the processing of the mutant G5. Login to comment
202 No mature G5 was present in cells expressing G5 with the R389H, R419H, or N437K mutations. Login to comment
220 These analyses were performed using a trafficking-defective mutant of G5, N437K. Login to comment
246 When the trafficking-defective mutant of G5 (N437K) was coexpressed with G8, the pattern of G5 was virtually identical to that obtained when G5 was expressed alone, indicating that the presence of G8 had no effect on the size or on the processing of the mutant G5. Login to comment
245 When the trafficking-defective mutant of G5 (N437K) was coexpressed with G8, the pattern of G5 was virtually identical to that obtained when G5 was expressed alone, indicating that the presence of G8 had no effect on the size or on the processing of the mutant G5. Login to comment

[hide] Clinical observations, molecular genetic analysis,... J Inherit Metab Dis. 2010 Aug;33(4):437-43. Epub 2010 Jun 3. Niu DM, Chong KW, Hsu JH, Wu TJ, Yu HC, Huang CH, Lo MY, Kwok CF, Kratz LE, Ho LT
Clinical observations, molecular genetic analysis, and treatment of sitosterolemia in infants and children.
J Inherit Metab Dis. 2010 Aug;33(4):437-43. Epub 2010 Jun 3., [PMID:20521169]

Abstract [show]
The clinical observation and treatment of young children with sitosterolemia has rarely been reported. We report clinical, biochemical, and molecular genetic observations and treatment outcomes for five Chinese children from four separate families presenting with sitosterolemia in whom we identified two new (Y329X, G269R) and three known (R446X, N437K, R389H) mutations in the ABCG5 gene. The R389H mutation was found in 50% of alleles. Three of these five patients received cholestyramine therapy with a very good response. However, all patients discontinued this therapy because of poor compliance. Finally, all patients were on ezetimibe therapy and had satisfactory total serum cholesterol levels, though their plant sterol levels were still higher than normal. Another noteworthy finding is that a female infant had a serum cholesterol level of 654 mg/dl at 7 months of age, despite being breast fed (with very tiny amounts of plant sterols) since birth and undergoing 4 months of ezetimibe administration. Although she failed to respond to ezetimibe during this period, she did show improvement when the therapy was started again at 2 years of age. It is possible that another 23-month-old female patient also responded more slowly to ezetimibe treatment than older patients.

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Sentences [show]
No. Sentence Comment
1 We report clinical, biochemical, and molecular genetic observations and treatment outcomes for five Chinese children from four separate families presenting with sitosterolemia in whom we identified two new (Y329X, G269R) and three known (R446X, N437K, R389H) mutations in the ABCG5 gene. Login to comment
23 Large peaks of serum plant sterols were identified by nuclear magnetic resonance (NMR) spectroscopy, but the exact concentrations of these sterols were unable to be Table 1 Baseline lipid profiles, liver enzymes, and blood cell counts of each study patient Patient no Normal values 1 2 3 4 5 Age at diagnosis 8 years 18 months 3 months 23 months 12 years Mutation (ABCG5) Y329X R389H R389H R389H R389H N437K R446X R446X R389H G269R Initial diagnostic data Cholesterol, mg/dl Total 125-240 427 705 402 640 343 Low-density-lipoprotein 60-150 346 565 304 519 263 High-density-lipoprotein 35-84 59 64 42 64 50 Total triglycerides, mg/dl 20-200 111 149 395a 98 98 Liver enzymes Alanine transaminase, U/l 5-45 10 13 45 15 44 Aspartate aminotransferase, U/l 15-55 19 31 100 31 37 Blood count Erythrocytes, count/µl 3.7×109 -5.3×109 3.35×109 4.25×109 3.98×109 4.49×109 4.46×109 Hemoglobin, g/dl 11.5-15.5 9.8 11.8 11 12.7 12.9 Mean corpuscular volume, fl 80-95 88.5 89.0 80.6 80.2 86 White blood cells, count/µl 4,500-17,500 7,200 6,900 6,700 11,200 5,200 Platelets, count/mm3 150×106 -350×106 211×106 289×106 506×106 566×106 293×106 After ezetimibe therapy Age at plant sterols analysis NA 5 years 3 years 3 year 13 year Duration of ezetimibe treatment NA 3 years 1 year 1 year 6 months Cholesterol, total (mg/dl) 125-240 NA 181 208 223 193 Sitosterol mg/dlb 0.216±0.220 (SD)c NA 7.10 9.17 7.07 6.14 Campesterol mg/dlb 0.309±0.165 (SD)c NA 3.79 4.78 4.04 4.22 NA not available a In the nonfasting state b Plant sterols were measured by gas chromatography/mass spectrometry, as previously described (Kwiterovich et al. 2003). Login to comment
77 The other mutation, N437K (c.1311C>G), located in exon 9, substituted an asparagine to a lysine at codon 437. Login to comment
75 Results of mutation analyses Patient 1 had compound heterozygous mutations, p.Y329X and p.N437K. Login to comment

[hide] Increased plasma plant sterol concentrations and a... Eur J Med Genet. 2011 Jul-Aug;54(4):e458-60. Epub 2011 May 23. Keller S, Prechtl D, Aslanidis C, Ceglarek U, Thiery J, Schmitz G, Jahreis G
Increased plasma plant sterol concentrations and a heterozygous amino acid exchange in ATP binding cassette transporter ABCG5: a case report.
Eur J Med Genet. 2011 Jul-Aug;54(4):e458-60. Epub 2011 May 23., [PMID:21664501]

Abstract [show]
Whilst conducting a scientific study, an elevated plasma plant sterol concentration of 3.07 mg/dL was established in one proband. Similar levels found in his mothers plasma (2.73 mg/dL) were suggestive of a heterozygous sitosterolemia. The resulting gene analysis for ATP binding cassette transporter G5/G8 (ABCG5/G8) revealed a heterozygous polymorphism in ABCG8 (Thr400Lys, rs4148217), which the proband had inherited from his father. However, a heterozygous amino acid exchange (Arg406Gln) in exon 9 of ABCG5 was revealed, which was inherited from his mother. Although not sufficient evidence exists to regard this sequence variation as a mutation, this previously unreleased sequence variation occurred in a "hot spot" area for sitosterolemia of the ABCG5 gene (exon 9) and the similar increased plasma plant sterol concentrations of the heterozygous mother contribute to the notion, that this very likely presents an inactivating mutation.

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No. Sentence Comment
57 In addition to splicing, insertions, deletion, and complete rearrangement of the ABCG5 gene,13 mutations with an amino acid exchange resulting in sitosterolemia are published (Gln22Term [14], Glu77Term [15], Glu146Gln [16], Arg243Term [17], Gly269Arg, Tyr329Term [7], Arg389His, Arg408Term, Arg419His, Arg419Pro [17], Asn437Lys [18], Arg446Term [1], Arg550Ser [16]). Login to comment
58 Five of the 13 mutations are located in exon 9 of the ABCG5 gene (Arg389His, Arg408Term, Arg419His, Arg419Pro, Asn437Lys) corresponding to our findings regarding the amino acid exchange Arg406Gln. Login to comment