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See detailIn search of a physiological role for thiamine triphosphate and the 25-kDa thiamine triphosphatase
Bettendorff, Lucien ULg; Lakaye, Bernard ULg; Kohn, Grégory ULg et al

Conference (2014, May 25)

In search of a physiological role for thiamine triphosphate and the 25-kDa thiamine triphosphatase L. BETTENDORFF, B. LAKAYE, G. KOHN AND P. WINS GIGA-Neurosciences, University of Liège, 4000-Liège ... [more ▼]

In search of a physiological role for thiamine triphosphate and the 25-kDa thiamine triphosphatase L. BETTENDORFF, B. LAKAYE, G. KOHN AND P. WINS GIGA-Neurosciences, University of Liège, 4000-Liège, Belgium Thiamine triphosphate (ThTP) was discovered over 60 years ago. Although it is present in most organisms from bacteria to mammals, its possible biological functions remain unclear. In contrast to thiamine diphosphate (ThDP), it is not a coenzyme. In E. coli cells, ThTP is transiently produced in response to amino acid starvation, while in mammalian cells, it is constitutively produced at a low rate. In some animal tissues, ThTP was able to phosphorylate proteins and activate a high-conductance anion channel in vitro. These observations raised the possibility of ThTP being part of a still uncharacterized cellular signaling pathway. Though it was long thought that ThTP is synthesized by a specific ThDP:ATP phosphotransferase, more recent studies indicate that two main mechanisms are involved: (1) in the cytosol adenylate kinase 1 can catalyze ThTP production from ThDP and ADP and (2) in brain mitochondria FoF1-ATP synthase can catalyze ThTP production from ThDP + Pi. The latter reaction is energized by the respiratory chain through a chemiosmotic mechanism analogous to oxidative phosphorylation. Both mechanisms are conserved from bacteria to mammals. While ThTP synthesis does not seem to require a specific enzyme, its hydrolysis in mammalian tissues is catalyzed by a very specific cytosolic 25 kDa thiamine triphosphatase (ThTPase). Because of this activity, steady-state ThTP levels are kept low in mammalian cells. ThTPase belongs to the CYTH superfamily of proteins which has representatives in all superkingdoms of life acting on tripolyphosphate and various triphosphorylated substrates. Although the whole chromosome region containing the ThTPase gene was lost in birds, orthologs of the ThTPase gene were found in all other known metazoan genomes. It seems that ThTPase activity appeared as a secondary acquisition of the CYTH proteins in the lineage leading from cnidarians to vertebrates. In particular, the Trp-53 residue of mammalian ThTPases plays a key role in substrate recognition and specificity by interacting with the thiazole part of ThTP. This residue is conserved in metazoan CYTH proteins with ThTPase activity. In order to gain insight into the physiological function(s) of the ThTP-ThTPase couple, we tried to produce a mouse invalidated in 25-kDa ThTPase. Surprisingly, we were unable to obtain any knockout animal, apparently because ThTPase seems to be required for spermatogenesis. As we previously showed that the enzyme is much more abundant in differentiated versus undifferentiated cells, we suspect that 25-kDa ThTPase might play a more general and important role during cell differentiation. Acknowledgments This work was supported by the F.R.S.-FNRS. LB and BL are respectively Research Director and Research Associate at the F.R.S.-FNRS. [less ▲]

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See detail25KDa-Thiamine triphosphatase is essential for spermatozoid development in mice
Kohn, Grégory ULg; Ectors, Fabien ULg; Lakaye, Bernard ULg et al

Poster (2014, May)

For many years, our laboratory has been interested in thiamine triphosphate (ThTP), a vitamin B1 derivative whose metabolism and physiological role remain unclear. Regarding its production, we have shown ... [more ▼]

For many years, our laboratory has been interested in thiamine triphosphate (ThTP), a vitamin B1 derivative whose metabolism and physiological role remain unclear. Regarding its production, we have shown that in E. coli and in rat brain mitochondria, ThTP is synthesized from thiamine diphosphate and inorganic phosphate through a chemiosmotic mechanism involving the FoF1- ATP synthase [1, 2]. In mammalian cells, its concentration is maintained at a low level through hydrolysis by a very specific cytosolic 25-kDa thiamine triphosphatase (ThTPase) [3]. In order to gain insight in the role of ThTP and ThTPase in mammalian tissues, we decided to generate a mouse strain invalidated in 25kDa-ThTPase with the hope that these mice will accumulate ThTP in their tissues. We obtained genetically modified embryonic stem (ES) cells from the Knockout Mouse Project (KOMP) repository. In those cells, one of the 25kDa-ThTPase alleles was replaced by a construction containing the lacZ and the neomycin resistance genes. Those ES cells were microinjected in blastocysts and the chimeric blastocysts were injected in a mouse uterus to generate chimerae. However, when we bred those mice with wild type mice, the construction was never transmitted to the pups. To explain this result, we selected those chimerae that presented a sex-reversal. In those mice, all the spermatozoids derive from the injected embryonic stem cells, so that half of the spermatozoids are expected to harbor the construction. However, after qPCR analysis, we observed that the spermatozoids with the construction were outnumbered by a factor of thousand. These results strongly suggest that the 25kDa-ThTPase is required for spermatozoid development. 1. Gangolf, M., Wins, P., Thiry, M., El Moualij, B. & Bettendorff, L. (2010) J. Biol. Chem. 285, 583-94. 2. Gigliobianco, T., Gangolf, M., Lakaye, B., Pirson, B., von Ballmoos, C., Wins, P. & Bettendorff, L. (2013) Scientific reports. 3, 1071. 3. Lakaye, B., Makarchikov, A. F., Antunes, A. F., Zorzi, W., Coumans, B., De Pauw, E., Wins, P., Grisar, T. & Bettendorff, L. (2002) J. Biol. Chem. 277, 13771-7. [less ▲]

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See detailStructural Determinants of Specificity and Catalytic Mechanism in mammalian 25-kDa Thiamine Triphosphatase
Delvaux, David; Kerff, Frédéric ULg; Murty, Mamidanna R.V.S. et al

in Biochimica et Biophysica Acta - General Subjects (2013), 1830

Background: Thiamine triphosphate (ThTP) is present in most organisms and might be involved in intracellular signaling. In mammalian cells, the cytosolic ThTP level is controlled by a specific thiamine ... [more ▼]

Background: Thiamine triphosphate (ThTP) is present in most organisms and might be involved in intracellular signaling. In mammalian cells, the cytosolic ThTP level is controlled by a specific thiamine triphosphatase (ThTPase), belonging to the CYTH superfamily of proteins. CYTH proteins are present in all superkingdoms of life and act on various triphosphorylated substrates. Methods: Using crystallography, mass spectrometry and mutational analysis, we identified the key structural determinants of the high specificity and catalytic efficiency of mammalian ThTPase. Results: Triphosphate binding requires three conserved arginines while the catalytic mechanism relies on an unusual lysine-tyrosine dyad. By docking of the ThTP molecule in the active site, we found that Trp-53 should interact with the thiazole part of the substrate molecule, thus playing a key role in substrate recognition and specificity. Sea anemone and zebrafish CYTH proteins, which retain the corresponding Trp residue, are also specific ThTPases. Surprisingly, the whole chromosome region containing the ThTPase gene is lost in birds. Conclusion: The specificity for ThTP is linked to a stacking interaction between the thiazole heterocycle of thiamine and a tryptophan residue. The latter likely plays a key role in the secondary acquisition of ThTPase activity in early metazoan CYTH enzymes, in the lineage leading from cnidarians to mammals. General significance: We show that ThTPase activity is not restricted to mammals as previously thought but is an acquisition of early metazoans. This, and the identification of critically important residues, allows us to draw an evolutionary perspective of the CYTH family of proteins. [less ▲]

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See detailHigh inorganic triphosphatase activities in bacteria and mammalian cells: Identification of the enzymes involved.
Kohn, Grégory ULg; Delvaux, David ULg; Lakaye, Bernard ULg et al

in PLoS ONE (2012), 7(9), 43879

Background: We recently characterized a specific inorganic triphosphatase (PPPase) from Nitrosomonas europaea. This enzyme belongs to the CYTH superfamily of proteins. Many bacterial members of this ... [more ▼]

Background: We recently characterized a specific inorganic triphosphatase (PPPase) from Nitrosomonas europaea. This enzyme belongs to the CYTH superfamily of proteins. Many bacterial members of this family are annotated as predicted adenylate cyclases, because one of the founding members is CyaB adenylate cyclase from A. hydrophila. The aim of the present study is to determine whether other members of the CYTH protein family also have a PPPase activity, if there are PPPase activities in animal tissues and what enzymes are responsible for these activities. Methodology/Principal Findings: Recombinant enzymes were expressed and purified as GST- or His-tagged fusion proteins and the enzyme activities were determined by measuring the release of inorganic phosphate. We show that the hitherto uncharacterized E. coli CYTH protein ygiF is a specific PPPase, but it contributes only marginally to the total PPPase activity in this organism, where the main enzyme responsible for hydrolysis of inorganic triphosphate (PPPi) is inorganic pyrophosphatase. We further show that CyaB hydrolyzes PPPi but this activity is low compared to its adenylate cyclase activity. Finally we demonstrate a high PPPase activity in mammalian and quail tissue, particularly in the brain. We show that this activity is mainly due to Prune, an exopolyphosphatase overexpressed in metastatic tumors where it promotes cell motility. Conclusions and General Significance: We show for the first time that PPPase activities are widespread in bacteria and animals. We identified the enzymes responsible for these activities but we were unable to detect significant amounts of PPPi in E. coli or brain extracts using ion chromatography and capillary electrophoresis. The role of these enzymes may be to hydrolyze PPPi, which could be cytotoxic because of its high affinity for Ca2+, thereby interfering with Ca2+ signaling. [less ▲]

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See detailMolecular evolution of the CYTH superfamily of proteins
Bettendorff, Lucien ULg; Delvaux, David ULg; Kohn, Grégory ULg et al

in FEBS Journal (2012), 279(Suppl. s1), 438

Molecular evolution of the CYTH superfamily of proteins L. Bettendorff, D. Delvaux, G. Kohn, P. Wins, B. Lakaye GIGA-Neurosciences, University of Liège, Belgium The CYTH superfamily of proteins was named ... [more ▼]

Molecular evolution of the CYTH superfamily of proteins L. Bettendorff, D. Delvaux, G. Kohn, P. Wins, B. Lakaye GIGA-Neurosciences, University of Liège, Belgium The CYTH superfamily of proteins was named after the two founding members, the CYaB adenylyl cyclase from Aeromonas hydrophila and the human 25-kDa THiamine triphosphatase (ThTPase). Members of this superfamily of proteins exist in all organisms including bacteria, archaea, plants and animals (except in birds) and can be traced back to the Last Universal Common Ancestor. They are characterized by a consensus sequence including several charged residues involved in divalent cation and triphosphate binding. Indeed, all members of the CYTH family that are characterized act on triphosphate derivatives and require at least one divalent cation for catalysis. The Nitrosomonas europaea (1) and E.coli CYTH proteins are specific inorganic triphosphatases. We propose that inorganic triphosphate (PPPi), the most simple triphosphate compound that can be imagined, is the primitive substrate of CYTH proteins. Other enzyme activities such as adenylate cyclase (in A. hydrophila), mRNA triphosphatase (in fungi and protozoans) and ThTPase (in metazoans) activities are secondary acquisitions. We show that ThTPase activity is not limited to mammals, but Sea anemone and Zebrafish CYTH proteins are already specific ThTPases and the acquisition of this enzyme activity is linked to the presence of a Trp (W53 in mammalian ThTPases) residue involved in the binding of the thiazole heterocycle of the thiamine molecule. The importance of W53 for the specificity of mammalian ThTPases is confirmed by site-directed mutagenesis. Furthermore, we propose a conserved catalytic mechanism between inorganic triphosphatases and ThTPases, based on a catalytic dyad comprising a Lys and a Tyr residue, explaining the alkaline pH optimum of CYTH proteins. (1) Delvaux et al. J. Biol. Chem 286 (2011) 34023-35 [less ▲]

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See detailA specific inorganic triphosphatase from Nitrosomonas europaea: structure and catalytic mechanism
Delvaux, David ULg; Murty, Mamidana R.V.S; Gabelica, Valérie ULg et al

in Journal of Biological Chemistry (2011), 286

The CYTH superfamily of proteins is named after its two founding members, the CyaB adenylyl cyclase from Aeromonas hydrophila and the human 25-kDa thiamine triphosphatase. Because these proteins often ... [more ▼]

The CYTH superfamily of proteins is named after its two founding members, the CyaB adenylyl cyclase from Aeromonas hydrophila and the human 25-kDa thiamine triphosphatase. Because these proteins often form a closed β-barrel, they are also referred to as “Triphosphate Tunnel Metalloenzymes” (TTM). Functionally, they are characterized by their ability to bind triphosphorylated substrates and divalent metal ions. These proteins exist in most organisms and catalyze different reactions, depending on their origin. Here we investigate structural and catalytic properties of the recombinant TTM protein from Nitrosomonas europaea (NeuTTM), a 19-kDa protein. Crystallographic data show that it crystallizes as a dimer and that, in contrast to other TTM proteins, it has an open β-barrel structure. We demonstrate that NeuTTM is a highly specific inorganic triphosphatase, hydrolyzing tripolyphosphate (PPPi) with high catalytic efficiency in the presence of Mg2+. These data are supported by native mass spectrometry analysis showing that the enzyme binds PPPi (and Mg-PPPi) with high affinity (Kd < 1.5 μM), while it has a low affinity for ATP or thiamine triphosphate. In contrast to Aeromonas and Yersinia CyaB proteins, NeuTTM has no adenylyl cyclase activity, but it shares several properties with other enzymes of the CYTH superfamily, e.g. heat-stability, alkaline pH optimum and inhibition by Ca2+ and Zn2+ ions. We suggest a catalytic mechanism involving a catalytic dyad formed by K52 and Y28. The present data provide the first characterization of a new type of phosphohydrolase (unrelated to pyrophosphatases or exopolyphosphatases), able to hydrolyze inorganic triphosphate with high specificity. [less ▲]

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