Enzymatic activation of pyruvate kinase increases cytosolic oxaloacetate to inhibit the Warburg effect.

Pharmacological activation of the glycolytic enzyme PKM2 or expression of the constitutively active PKM1 isoform in cancer cells results in decreased lactate production, a phenomenon known as the PKM2 paradox in the Warburg effect. Here we show that oxaloacetate (OAA) is a competitive inhibitor of human lactate dehydrogenase A (LDHA) and that elevated PKM2 activity increases de novo synthesis of OAA through glutaminolysis, thereby inhibiting LDHA in cancer cells. We also show that replacement of human LDHA with rabbit LDHA, which is relatively resistant to OAA inhibition, eliminated the paradoxical correlation between the elevated PKM2 activity and the decreased lactate concentration in cancer cells treated with a PKM2 activator.

Reductive amination of α-Ketoglutarate in metabolite extracts results in glutamate overestimation.

Artifacts due to metabolite extraction, derivatization, and detection techniques can result in aberrant observations that are not accurate representations of actual cell metabolism. Here, we show that α-ketoglutarate (α-KG) is reductively aminated to glutamate in methanol:water metabolite extracts, which introduces an artifact into metabolomics studies. We also identify pyridoxamine and urea as amine donors for α-KG to produce glutamate in methanol:water buffer in vitro, and we demonstrate that the addition of ninhydrin to the methanol:water buffer suppresses the reductive amination of α-KG to glutamate in vitro and in metabolite extracts.

Enzymatic and metabolic regulation of lysine succinylation.

Lysine succinylation (Ksucc), defined as a transfer of a succinyl group to a lysine residue of a protein, is a newly identified protein post-translational modification. This chemical modification is reversible, dynamic, and evolutionarily conserved where it has been comprehensively studied in both bacterial and mammalian cells. Numerous proteins involved in the regulation of various cellular and biological processes have been shown to be heavily succinylated.

Tyrosine Phosphorylation of Mitochondrial Creatine Kinase 1 Enhances a Druggable Tumor Energy Shuttle Pathway.

How mitochondrial metabolism is altered by oncogenic tyrosine kinases to promote tumor growth is incompletely understood. Here, we show that oncogenic HER2 tyrosine kinase signaling induces phosphorylation of mitochondrial creatine kinase 1 (MtCK1) on tyrosine 153 (Y153) in an ABL-dependent manner in breast cancer cells. Y153 phosphorylation, which is commonly upregulated in HER2 breast cancers, stabilizes MtCK1 to increase the phosphocreatine energy shuttle and promote proliferation.

Tyrosine Kinase Signaling in Cancer Metabolism: PKM2 Paradox in the Warburg Effect.

The Warburg Effect, or aerobic glycolysis, is one of the major metabolic alterations observed in cancer. Hypothesized to increase a cell's proliferative capacity via regenerating NAD, increasing the pool of glycolytic biosynthetic intermediates, and increasing lactate production that affects the tumor microenvironment, the Warburg Effect is important for the growth and proliferation of tumor cells. The mechanisms by which a cell acquires the Warburg Effect phenotype are regulated by the expression of numerous oncogenes, including oncogenic tyrosine kinases.

Carnitine Palmitoyltransferase 1A Has a Lysine Succinyltransferase Activity.

Lysine succinylation was recently identified as a post-translational modification in cells. However, the molecular mechanism underlying lysine succinylation remains unclear. Here, we show that carnitine palmitoyltransferase 1A (CPT1A) has lysine succinyltransferase (LSTase) activity in vivo and in vitro.