Targeted killing of a mammalian cell based upon its specialized metabolic state

Abstract

Mouse ES cells use a mitochondrial threonine dehydrogenase (TDH) enzyme to catabolize threonine into glycine and acetylCoA. Measurements of mRNA abundance have given evidence that ES cells express upwards of 1,000-fold higher levels of TDH mRNA than any of seven other mouse tissues tested. When cell culture medium is deprived of threonine, ES cells rapidly discontinue DNA synthesis, arrest cell division, and eventually die. Such studies led to the conclusion that mouse ES cells exist in a threonine-dependent metabolic state. Proceeding with the assumption that the active TDH enzyme should be essential for the growth and viability of mouse ES cells, we performed a drug screen in search of specific inhibitors of the purified TDH enzyme. Such efforts led to the discovery of a class of quinazolinecarboxamide (Qc) compounds that inhibit the ability of the TDH enzyme to catabolize threonine into glycine and acetyl-CoA. Administration of Qc inhibitors of TDH to mouse ES cells impeded cell growth and resulted in the induction of autophagy. By contrast, the same chemicals failed to affect the growth of HeLa cells at concentrations 300-fold higher than that required to kill mouse ES cells. It was likewise observed that the Qc class of TDH inhibitors failed to affect the growth or viability of ES cell-derived embryoid body cells known to have extinguished TDH expression. These studies demonstrate how it is possible to kill a specific mammalian cell type on the basis of its specialized metabolic state.specialized metabolism | threonine catabolism | embryonic stem cells T he diverse spectrum of life forms found in nature makes use of a variety of specialized metabolic pathways to support growth and reproduction. Over the past century, these often unanticipated specializations in metabolism have enabled scientists to pharmacologically poison specific organisms or cell types to the benefit of human health. One of the first examples of the utility of this strategy was the sulfonamide class of antibiotics. Discovered in the 1930s, sulfonamides act by inhibiting the bacterial enzyme dihydropteroate synthetase (DHPS) (1, 2). The DHPS enzyme is needed by bacteria to synthesize folic acid derivatives, which are required for the de novo synthesis of nucleotides. Mammals do not encode DHPS enzymes and instead obtain folates from their diet. For this reason sulfonamides are well tolerated by humans. A second example of an antibiotic that works by exploiting metabolic specialization is metronidazole. Metronidazole becomes toxic only after being reduced in the absence of oxygen; hence this chemical toxin selectively targets anaerobic microorganisms (3). Many drugs that block the growth of eukaryotic pathogens also work by attacking points of vulnerability built around specialized differences in metabolism. These include the azole, echinocandin, and allylamine classes of antifungal drugs (4-6), as well as the antiparasitics thiabendazole and diethylcarbazamine (7,8).Human cancer cells have also been targeted by virtue of their specialized...

The TDH–GCN5L1–Fbxo15–KBP axis limits mitochondrial biogenesis in mouse embryonic stem cells

“…2a–b). Short treatment of mESCs with Qc-1, a pharmacological inhibitor of TDH that impairs the production of acetylCoA in mESCs 27 , resulted in an increase of both KBP protein level and half-life (Supplementary Fig. 3b–c).…”

Stem cell metabolism in tissue development and aging

“…Like TDH, GLDC is also upregulated in pluripotent cells relative to differentiated cells . Furthermore, pharmacological inhibition or knockdown of TDH disrupts mouse ESC colony growth (Alexander et al, 2011;. Collectively, these findings suggest that the metabolites generated by Thr degradation may be used specifically for the self-renewal of pluripotent ESCs.…”

Metabolic determinants of embryonic development and stem cell fate

“…Mouse pluripotent stem cells express high levels of threonine dehydrogenase, which catalyzes the first step of conversion of the amino acid threonine into glycine and acetyl-CoA (Wang et al 2009; Shyh-Chang et al 2013). Removal of threonine from cell culture impairs stem cell proliferation, while inhibition of threonine dehydrogenase disrupts stem cell colony growth and impairs the nuclear reprogramming (Wang et al 2009; Alexander et al 2011; Han et al 2013; Shyh-Chang et al 2013). Glycine produced from threonine catabolism is further catabolized by glycine decarboxylase to provide 1-carbon equivalents for the folate pool, which ultimately supports the S-adenosylmethionine pathway and regulation of histone H3K4 methylation, which is critical for pluripotent stem cell function (Shyh-Chang et al 2013).…”