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Analysis of the Qatari R336C cystathionine ?-synthase protein in mice.

ABSTRACT: Classical homocystinuria is a recessive inborn error of metabolism caused by mutations in the cystathionine beta-synthase (CBS) gene. The highest incidence of CBS deficiency in the world is found in the country of Qatar due to the combination of high rates of consanguinity and the presence of a founder mutation, c.1006C>T (p.R336C). This mutation does not respond to pyridoxine and is considered severe. Here we describe the creation of a mouse that is null for the mouse Cbs gene and expresses human p.R336C CBS from a zinc-inducible transgene (Tg-R336C Cbs -/- ). Zinc-treated Tg-R336C Cbs -/- mice have extreme elevation in both serum total homocysteine (tHcy) and liver tHcy compared with control transgenic mice. Both the steady-state protein levels and CBS enzyme activity levels in liver lysates from Tg-R336C Cbs -/- mice are significantly reduced compared to that found in Tg-hCBS Cbs -/- mice expressing wild-type human CBS. Treatment of Tg-R336C Cbs -/- mice with the proteasome inhibitor bortezomib results in stabilization of liver CBS protein and an increase in activity to levels found in corresponding Tg-hCBS Cbs -/- wild type mice. Surprisingly, serum tHcy did not fully correct even though liver enzyme activity was as high as control animals. This discrepancy is explained by in vitro enzymatic studies of mouse liver extracts showing that p.R336C causes reduced binding affinity for the substrate serine by almost 7-fold and significantly increased dependence on pyridoxal phosphate in the reaction buffer. These studies demonstrate that the p.R336C alteration effects both protein stability and substrate/cofactor binding.

SUBMITTER: Gupta S

PROVIDER: S-EPMC7336392 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Analysis of the Qatari R336C cystathionine β-synthase protein in mice.

Gupta Sapna S Gallego-Villar Lorena L Wang Liqun L Lee Hyung-Ok HO Nasrallah Gheyath G Al-Dewik Nader N Häberle Johannes J Thöny Beat B Blom Henk J HJ Ben-Omran Tawfeg T Kruger Warren D WD

Journal of inherited metabolic disease 20190710 5

Classical homocystinuria is a recessive inborn error of metabolism caused by mutations in the cystathionine beta-synthase (CBS) gene. The highest incidence of CBS deficiency in the world is found in the country of Qatar due to the combination of high rates of consanguinity and the presence of a founder mutation, c.1006C>T (p.R336C). This mutation does not respond to pyridoxine and is considered severe. Here we describe the creation of a mouse that is null for the mouse Cbs gene and expresses hum ...[more]

PMID: 31240737

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Project description:Hydrogen sulfide (H2S) has been proposed to exert pro- as well as anti-inflammatory effects in various models of critical illness. In this study, we compared bacterial lipopolysaccharide (LPS)‑induced changes in inflammatory mediator production, indices of multiple organ injury and survival in wild‑type (WT) mice and in mice with reduced expression of one of the three H2S‑producing enzymes, cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS) or 3-mercaptopyruvate sulfurtransferase (3MST). Mice were injected intraperitoneally (i.p.) with LPS (10 mg/kg). After 6 h, the animals were sacrificed, blood and organs were collected and the following parameters were evaluated: blood urea nitrogen (BUN) levels in blood, myeloperoxidase (MPO) and malondialdehyde (MDA) in the lung, cytokine levels in plasma and the expression of the three H2S‑producing enzymes (CBS, CSE and 3MST) in the spleen, lung, liver and kidney. LPS induced a tissue‑dependent upregulation of some of the H2S‑producing enzymes in WT mice (upregulation of CBS in the spleen, upregulation of 3MST in the liver and upregulation of CBS, CSE and 3MST in the lung). Moreover, LPS impaired glomerular function, as evidenced by increased BUN levels. Renal impairment was comparable in the CSE‑/‑ and Δ3MST mice after LPS challenge; however, it was attenuated in the CBS+/‑ mice. MPO levels (an index of neutrophil infiltration) and MDA levels (an index of oxidative stress) in lung homogenates were significantly increased in response to LPS; these effects were similar in the WT, CBS+/‑, CSE‑/‑ and Δ3MST mice; however, the MDA levels tended to be lower in the CBS+/‑ and CSE‑/‑ mice. LPS induced significant increases in the plasma levels of multiple cytokines [tumor necrosis factor (TNF)α, interleukin (IL)‑1β, IL‑6, IL‑10, IL‑12 and interferon (IFN)γ] in plasma; TNFα, IL‑10 and IL‑12 levels tended to be lower in all three groups of animals expressing lower levels of H2S‑producing enzymes. The survival rates after the LPS challenge did not show any significant differences between the four animal groups tested. Thus, the findings of this study indicate that a deficiency in 3MST does not significantly affect endotoxemia, while a deficiency in CBS or CSE slightly ameliorates the outcome of LPS-induced endotoxemia in vivo.

Dataset Information

Analysis of the Qatari R336C cystathionine ?-synthase protein in mice.

Publications

Analysis of the Qatari R336C cystathionine β-synthase protein in mice.

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