Cystathionine β-synthase deficiency: Of mice and men

Kruger, Warren D.

doi:10.1016/j.ymgme.2017.05.011

Cited by 52 publications

(45 citation statements)

References 74 publications

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“…These results indicate the possibility of CBS being present in the mitochondria as well. Although primarily cytosolic, under extraordinary external and internal stress, such as deranged metabolism or hypoxia, CBS can also be found in the mitochondria (27). In addition, a previous report demonstrated a mitochondriontargeting sequence in the C-terminal regulatory domain of CBS (33).…”

Section: Cbs Regulates Mfn2 Expressionmentioning

confidence: 97%

“…Interestingly, CBS is highly expressed in the brain, where it is postulated to be the physiologic source of H 2 S (25), whereas cystathionine g-lysse, another H 2 Sproducing enzyme, is more preferentially expressed in peripheral tissues (26). However, CBS and consequential H 2 S production have been shown to be upregulated in various types of peripheral tissue cancer, including ovarian, colon, breast, and lung cancer (27). This increase in CBS expression has been shown to stimulate cellular bioenergetics, tumor growth, and cellular proliferation (28).…”

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confidence: 99%

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Cystathionine β‐synthase regulates mitochondrial morphogenesis in ovarian cancer

et al. 2018

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Deregulation of mitochondrial morphogenesis, a dynamic equilibrium between mitochondrial fusion and fission processes, is now evolving as a key metabolic event that fuels tumor growth and therapy resistance. However, fundamental knowledge underpinning how cancer cells reprogram mitochondrial morphogenesis remains incomplete. Here, we report that cystathionine β-synthase (CBS) reprograms mitochondrial morphogenesis in ovarian cancer (OvCa) cells by selectively regulating the stability of mitofusin 2 (MFN2). Clinically, high expression of both CBS and MFN2 implicates poor overall survival of OvCa patients, and a significant association between CBS and MFN2 expression exists in individual patients in the same data set. The silencing of CBS by small interfering RNA or inhibition of its catalytic activity by a small molecule inhibitor creates oxidative stress that activates JNK. Activated JNK phosphorylates MFN2 to recruit homologous to the E6-AP carboxyl terminus' domain-containing ubiquitin E3 ligase for its degradation via the ubiquitin-proteasome system. Supplementation with hydrogen sulfide or glutathione (the catalytic products of CBS enzymatic activity), anti-oxidants, or a JNK inhibitor restores MFN2 expression. In CBS-silenced orthotopic xenograft tumor tissues, MFN2 but not MFN1 is selectively downregulated. In summary, this report reveals a role for deregulated mitochondrial morphogenesis in OvCa, suggests one of the mechanisms for this deregulation, and provides a way to correct it through modulation of the metabolic enzyme CBS.-Chakraborty, P. K., Murphy, B., Mustafi, S. B., Dey, A., Xiong, X., Rao, G., Naz, S., Zhang, M., Yang, D., Dhanasekaran, D. N., Bhattacharya, R., Mukherjee, P. Cystathionine β-synthase regulates mitochondrial morphogenesis in ovarian cancer.

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Section: Cbs Regulates Mfn2 Expressionmentioning

confidence: 97%

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confidence: 99%

Cystathionine β‐synthase regulates mitochondrial morphogenesis in ovarian cancer

et al. 2018

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“…Thus, as a proof of concept, we decided to use, in parallel, a well‐adapted laboratory cell line (HEK293T cells) that is relatively easy to transfect and capable of expressing sufficient amounts of CBS, which is well expressed in the kidney. In human and mouse, it is known that CBS is expressed predominantly in liver, pancreas, kidney, and brain (reviewed in Kruger, ). As shown in Figure A and B, wt‐HEK293T cells express high levels of CBS mRNA and protein, making them suitable for our study.…”

Section: Resultsmentioning

confidence: 99%

In silico and in vivo models for Qatari-specific classical homocystinuria as basis for development of novel therapies

et al. 2018

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Homocystinuria is a rare inborn error of methionine metabolism caused by cystathionine β‐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, ΔCBS 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 ΔCBS‐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.

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“…Adult Tg‐R336C Cbs −/− mice have extremely elevated tHcy (>300 μM) and are significantly smaller than their Cbs +/− and Cbs +/+ siblings. These elevated tHcy levels are similar to the tHcy levels observed in C57BL6 models of Cbs deficiency . Other noticeable differences include a slightly lighter coat color, mild facial alopecia, hypertrophy of liver cells, and a noticeable increase in cells undergoing mitosis.…”

Section: Discussionmentioning

confidence: 99%

“…These elevated tHcy levels are similar to the tHcy levels observed in C57BL6 models of Cbs deficiency. 26 Other noticeable differences include a slightly lighter coat color, mild facial alopecia, hypertrophy of liver cells, and a noticeable increase in cells undergoing mitosis. These phenotypes have all been observed in other mouse models of Cbs deficiency and probably reflect the toxic effects of highly elevated serum tHcy.…”

Section: Discussionmentioning

confidence: 99%

Analysis of the Qatari R336C cystathionine β‐synthase protein in mice

Gupta

Gallego

Wang

et al. 2019

J of Inher Metab Disea

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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.

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Cystathionine β-synthase deficiency: Of mice and men

Cited by 52 publications

References 74 publications

Cystathionine β‐synthase regulates mitochondrial morphogenesis in ovarian cancer

Cystathionine β‐synthase regulates mitochondrial morphogenesis in ovarian cancer

In silico and in vivo models for Qatari-specific classical homocystinuria as basis for development of novel therapies

Analysis of the Qatari R336C cystathionine β‐synthase protein in mice

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