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Ismail HM , Krishnamoorthy N , Al-Dewik N , Zayed H , Mohamed NA , Giacomo VD , Gupta S , Haberle J , Thony B , Blom HJ , Kruger WD , Ben-Omran T , Nasrallah GK
In silico and in vivo models for Qatari-specific classical homocystinuria as basis for development of novel therapies
Hum Mutat. 2019 Feb;40(2) :230-240
PMID: 30408270    PMCID: PMC6586426    URL: https://www.ncbi.nlm.nih.gov/pubmed/30408270
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Abstract
Homocystinuria is a rare inborn error of methionine metabolism caused by cystathionine beta-synthase (CBS) deficiency. The prevalence of homocystinuria in Qatar is 1:1,800 births, mainly due to a founder Qatari missense mutation, c.1006C>T; p.R336C (p.Arg336Cys). We characterized the structure-function relationship of the p.R336C-mutant protein and investigated the effect of different chemical chaperones to restore p.R336C-CBS activity using three models: in silico, DeltaCBS yeast, and CRISPR/Cas9 p.R336C knock-in HEK293T and HepG2 cell lines. Protein modeling suggested that the p.R336C induces severe conformational and structural changes, perhaps influencing CBS activity. Wild-type CBS, but not the p.R336C mutant, was able to restore the yeast growth in DeltaCBS-deficient yeast in a complementation assay. The p.R336C knock-in HEK293T and HepG2 cells decreased the level of CBS expression and reduced its structural stability; however, treatment of the p.R336C knock-in HEK293T cells with betaine, a chemical chaperone, restored the stability and tetrameric conformation of CBS, but not its activity. Collectively, these results indicate that the p.R336C mutation has a deleterious effect on CBS structure, stability, and activity, and using the chemical chaperones approach for treatment could be ineffective in restoring p.R336C CBS activity.
Notes
1098-1004 Ismail, Hesham M Krishnamoorthy, Navaneethakrishnan Al-Dewik, Nader Zayed, Hatem Mohamed, Nura A Giacomo, Valeria Di Gupta, Sapna Haberle, Johannes ORCID: https://orcid.org/0000-0003-0635-091X Thony, Beat Blom, Henk J Kruger, Waren D ORCID: https://orcid.org/0000-0002-4990-3695 Ben-Omran, Tawfeg Nasrallah, Gheyath K ORCID: https://orcid.org/0000-0001-9252-1038 NPR7-355-3-088/Qatar National Research Fund Journal Article United States Hum Mutat. 2019 Feb;40(2):230-240. doi: 10.1002/humu.23682. Epub 2018 Nov 23.