Abstract
Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is a classical metabolic enzyme involved in energy production and plays a role in additional nuclear functions, including transcriptional control, recognition of misincorporated nucleotides in DNA and maintenance of telomere structure. Here, we show that the recombinant protein T. cruzi GAPDH (rTcGAPDH) binds single-stranded telomeric DNA. We demonstrate that the binding of GAPDH to telomeric DNA correlates with the balance between oxidized and reduced forms of nicotinamide adenine dinucleotides (NAD+/NADH). We observed that GAPDH-telomere association and NAD+/NADH balance changed throughout the T. cruzi life cycle. For example, in replicative epimastigote forms of T. cruzi, which show similar intracellular concentrations of NAD+ and NADH, GAPDH binds to telomeric DNA in vivo and this binding activity is inhibited by exogenous NAD+. In contrast, in the T. cruzi non-proliferative trypomastigote forms, which show higher NAD+ concentration, GAPDH was absent from telomeres. In addition, NAD+ abolishes physical interaction between recombinant GAPDH and synthetic telomere oligonucleotide in a cell free system, mimicking exogenous NAD+ that reduces GAPDH-telomere interaction in vivo. We propose that the balance in the NAD+/NADH ratio during T. cruzi life cycle homeostatically regulates GAPDH telomere association, suggesting that in trypanosomes redox status locally modulates GAPDH association with telomeric DNA.
Highlights
Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is a classical metabolic enzyme involved in energy production but is thought of as a “moonlighting protein”, an idea firstPLOS ONE | DOI:10.1371/journal.pone.0120896 March 16, 2015Glyceraldehyde 3 Phosphate Dehydrogenase and Telomere Associations
We demonstrate that the NAD+/NADH balance and the ability of GAPDH to associate with telomeric DNA changes during the T. cruzi life cycle
We tested whether the recombinant T. cruzi GAPDH enzyme (X52898) was able to bind to telomeres using an electrophoretic mobility shift assay (EMSA)
Summary
Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is a classical metabolic enzyme involved in energy production but is thought of as a “moonlighting protein”, an idea first. Because this parasite is exposed to environmental changes during its life cycle and exhibits flexible metabolic activity, we tested GAPDH-telomeric DNA associations in parasite cells maintained in different cellular redox state. NAD+ abolishes physical interaction between recombinant-GAPDH and synthetic telomere-oligonucleotide in a cell-free system, mimicking exogenous NAD+ that reduces GAPDH-telomere interaction in vivo Taken together, these data suggest that the NAD+/NADH balance may control the association between GAPDH and telomeric DNA in trypanosomes so that telomere maintenance and metabolic control are coupled and occurred early during evolution
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