Heart Mitochondrial TTP Synthesis and the Compartmentalization of TMP

Kamath, Vasudeva; Hsiung, Chia-Heng; Lizenby, Zachary J.; McKee, Edward E.

doi:10.1074/jbc.m114.624213

Cited by 12 publications

(14 citation statements)

References 27 publications

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“…Despite the clear benefits of this therapy, we observed that most of the dCMP and dTMP were rapidly converted to their respective nucleosides, dC and dT, suggesting that these nucleosides were the active therapeutic agents. In support of our hypothesis, a study of mitochondria isolated from hearts of rats treated with radiolabeled dT and dTMP demonstrated that most of the mitochondrial TTP was generated from dT, rather than dTMP, and that exogenously administered dTMP was compartmentalized from dTMP synthesized from dT …”

Section: Discussionsupporting

confidence: 67%

“…In support of our hypothesis, a study of mitochondria isolated from hearts of rats treated with radiolabeled dT and dTMP demonstrated that most of the mitochondrial TTP was generated from dT, rather than dTMP, and that exogenously administered dTMP was compartmentalized from dTMP synthesized from dT. 20 In the present study, we initially tested a dose of 260mg/kg/day of dC1dT, which is the equimolar concentration of 400mg of dCMP1dTMP, and subsequently 520mg/kg/day of dC1dT. Interestingly, we observed that Tk2 -/-260 dC1dT mice had a life span equivalent to that of Tk2 -/-200 dCMP1dTMP , whereas Tk2 -/-520 dC1dT had a life span equivalent to that showed by Tk2 -/-400 dCMP1dTMP .…”

Section: Discussionsupporting

confidence: 66%

“…The reason for the different dose responses to dNMPs relative to deoxynucleosides is unclear. One potential explanation is that, whereas dC+dT functions as the active therapeutic agents as substrates enhancing Tk1, deoxycytidine kinase (Dck), and Tk2 activities, monophosphates may partially bypass the enzyme activity and partially function as prodrugs with conversion to nucleosides, as indicted by Kamath et al Furthermore, 5′‐nucleotidase activity might delay the release of dC/dT in tissues, improving dNMP efficacy relative to deoxynucleosides. Another possibility, based on HPLC data, is that further degradation of dC and dT to their bases limits their availability in tissues.…”

Section: Discussionmentioning

confidence: 99%

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Deoxycytidine and Deoxythymidine Treatment for Thymidine Kinase 2 Deficiency

Lopez‐Gómez

Levy

Sanchez-Quintero

et al. 2017

Annals of Neurology

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Objective Thymidine kinase 2 (TK2), a critical enzyme in the mitochondrial pyrimidine salvage pathway, is essential for mitochondrial DNA (mtDNA) maintenance. Mutations in the nuclear gene TK2 cause TK2 deficiency, which manifests predominantly in children as myopathy with mtDNA depletion. Molecular bypass therapy with the TK2 products, dCMP and dTMP, prolongs the lifespan of Tk2-deficient (Tk2-/-) mice by 2-3 fold. Because we observed rapid catabolism of the deoxynucleoside monophosphates to deoxythymidine (dT) and deoxycytidine (dC), we hypothesized that: 1) deoxynucleosides might be the major active agents and 2) inhibition of deoxycytidine deamination might enhance dTMP+dCMP therapy. Methods To test these hypotheses, we assessed two therapies in Tk2-/- mice: 1) dT+dC and 2) co-administration of the deaminase inhibitor, tetrahydrouridine (THU), with dTMP+dCMP. Results We observed that dC+dT delayed disease onset, prolonged lifespan of Tk2-deficient mice, and restored mtDNA copy number as well as respiratory chain enzyme activities and levels. In contrast, dCMP+dTMP+THU therapy decreased lifespan of Tk2-/- animals compared to dCMP+dTMP. Interpretation Our studies demonstrate that deoxynucleoside substrate enhancement is a novel therapy, which may ameliorate TK2 deficiency in patients.

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Section: Discussionsupporting

confidence: 67%

Section: Discussionsupporting

confidence: 66%

Section: Discussionmentioning

confidence: 99%

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Deoxycytidine and Deoxythymidine Treatment for Thymidine Kinase 2 Deficiency

Lopez‐Gómez

Levy

Sanchez-Quintero

et al. 2017

Annals of Neurology

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“…The modification of dTMP to dTTP can take place in mitochondria ( Scheme 1 ). In the literature, it is disputed whether TS exists in mitochondria [ 16 , 17 ] or not [ 18 ]. Even RNR might also be located in mitochondria [ 19 ].…”

Section: Discussionmentioning

confidence: 99%

Uridine Treatment of the First Known Case of SLC25A36 Deficiency

Jasper

Scarcia

Rust

et al. 2021

IJMS

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SLC25A36 is a pyrimidine nucleotide carrier playing an important role in maintaining mitochondrial biogenesis. Deficiencies in SLC25A36 in mouse embryonic stem cells have been associated with mtDNA depletion as well as mitochondrial dysfunction. In human beings, diseases triggered by SLC25A36 mutations have not been described yet. We report the first known case of SLC25A36 deficiency in a 12-year-old patient with hypothyroidism, hyperinsulinism, hyperammonemia, chronical obstipation, short stature, along with language and general developmental delay. Whole exome analysis identified the homozygous mutation c.803dupT, p.Ser269llefs*35 in the SLC25A36 gene. Functional analysis of mutant SLC25A36 protein in proteoliposomes showed a virtually abolished transport activity. Immunoblotting results suggest that the mutant SLC25A36 protein in the patient undergoes fast degradation. Supplementation with oral uridine led to an improvement of thyroid function and obstipation, increase of growth and developmental progress. Our findings suggest an important role of SLC25A36 in hormonal regulations and oral uridine as a safe and effective treatment.

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“…However, both L-FAC analogs were cross-reactive with mitochondrial thymidine kinase 2 (TK2), which, like dCK, lacks enantioselectivity and consequently phosphorylates deoxypyrimidines with both D-and L-enantiomeric configurations (16). In humans, cross-reactivity with TK2 was likely responsible for the uptake of the FAC analogs into the myocardium (12), a tissue with high TK2 expression (17).…”

mentioning

confidence: 99%

[ ¹⁸ F]CFA as a clinically translatable probe for PET imaging of deoxycytidine kinase activity

Kim

Liu

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Deoxycytidine kinase (dCK), a rate-limiting enzyme in the cytosolic deoxyribonucleoside (dN) salvage pathway, is an important therapeutic and positron emission tomography (PET) imaging target in cancer. PET probes for dCK have been developed and are effective in mice but have suboptimal specificity and sensitivity in humans. To identify a more suitable probe for clinical dCK PET imaging, we compared the selectivity of two candidate compounds—[18F]Clofarabine; 2-chloro-2′-deoxy-2′-[18F]fluoro-9-β-d-arabinofuranosyl-adenine ([18F]CFA) and 2′-deoxy-2′-[18F]fluoro-9-β-d-arabinofuranosyl-guanine ([18F]F-AraG)—for dCK and deoxyguanosine kinase (dGK), a dCK-related mitochondrial enzyme. We demonstrate that, in the tracer concentration range used for PET imaging, [18F]CFA is primarily a substrate for dCK, with minimal cross-reactivity. In contrast, [18F]F-AraG is a better substrate for dGK than for dCK. [18F]CFA accumulation in leukemia cells correlated with dCK expression and was abrogated by treatment with a dCK inhibitor. Although [18F]CFA uptake was reduced by deoxycytidine (dC) competition, this inhibition required high dC concentrations present in murine, but not human, plasma. Expression of cytidine deaminase, a dC-catabolizing enzyme, in leukemia cells both in cell culture and in mice reduced the competition between dC and [18F]CFA, leading to increased dCK-dependent probe accumulation. First-in-human, to our knowledge, [18F]CFA PET/CT studies showed probe accumulation in tissues with high dCK expression: e.g., hematopoietic bone marrow and secondary lymphoid organs. The selectivity of [18F]CFA for dCK and its favorable biodistribution in humans justify further studies to validate [18F]CFA PET as a new cancer biomarker for treatment stratification and monitoring.

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Heart Mitochondrial TTP Synthesis and the Compartmentalization of TMP

Cited by 12 publications

References 27 publications

Deoxycytidine and Deoxythymidine Treatment for Thymidine Kinase 2 Deficiency

Deoxycytidine and Deoxythymidine Treatment for Thymidine Kinase 2 Deficiency

Uridine Treatment of the First Known Case of SLC25A36 Deficiency

[ ¹⁸ F]CFA as a clinically translatable probe for PET imaging of deoxycytidine kinase activity

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Heart Mitochondrial TTP Synthesis and the Compartmentalization of TMP

Cited by 12 publications

References 27 publications

Deoxycytidine and Deoxythymidine Treatment for Thymidine Kinase 2 Deficiency

Deoxycytidine and Deoxythymidine Treatment for Thymidine Kinase 2 Deficiency

Uridine Treatment of the First Known Case of SLC25A36 Deficiency

[ 18 F]CFA as a clinically translatable probe for PET imaging of deoxycytidine kinase activity

Contact Info

Product

Resources

About

[ ¹⁸ F]CFA as a clinically translatable probe for PET imaging of deoxycytidine kinase activity