Evidence for an Alternative Glycolytic Pathway in Rapidly Proliferating Cells

Abstract

Proliferating cells, including cancer cells, require altered metabolism to efficiently incorporate nutrients such as glucose into biomass. The M2 isoform of pyruvate kinase (PKM2) promotes the metabolism of glucose by aerobic glycolysis and contributes to anabolic metabolism. Paradoxically, decreased pyruvate kinase enzyme activity accompanies the expression of PKM2 in rapidly dividing cancer cells and tissues. We demonstrate that phosphoenolpyruvate (PEP), the substrate for pyruvate kinase in cells, can act as a phosphate donor in mammalian cells as PEP participates in the phosphorylation of the glycolytic enzyme phosphoglycerate mutase (PGAM1) in PKM2 expressing cells. We used mass spectrometry to show that the phosphate from PEP is transferred to the catalytic histidine (His-11) on human PGAM1. This reaction occurred at physiological concentrations of PEP and produced pyruvate in the absence of PKM2 activity. The presence of histidine-phosphorylated PGAM1 correlated with the expression PKM2 in cancer cell lines and tumor tissues. Thus, decreased pyruvate kinase activity in PKM2-expressing cells allows PEP-dependent histidine phosphorylation of PGAM1, and may provide an alternate glycolytic pathway that decouples ATP production from PEP-mediated phosphotransfer, allowing for the high rate of glycolysis to support anabolic metabolism observed in many proliferating cells.

Spatial Distribution of Cellular Function: The Partitioning of Proteins between Mitochondria and the Nucleus in MCF7 Breast Cancer Cells

“…The present results suggest further investigation of the functional roles of glycolytic enzymes in mitochondria and the nucleus is needed, especially in the light of indications that they concentrate in the MAM region of mitochondria 84 and that mitochondrial restructuring and bioenergetic plasticity are also important for stem cell differentiation/regression. 96 Both PKM2 97,98 and PFKFB3 74 have recently been proposed as "master" proteins for controlling the metabolic changes involved in hypoxia, proliferation and cancer, but a substantial body of other literature and the present results suggest that much more complicated networks with feedback loops involving many glycolysis, TCAcycle, OxPhos and signaling proteins may be involved. Furthermore hypoxia causes dynamic changes in protein subcellular location involving functions that go far beyond changes in glycolysis and include TCA-cycle, OxPhos and chromatin remodeling proteins among many others.…”

Metabolic reprogramming of the tumor

“…Accordingly, augmented glucose fluxes avoid oxidative stress and delay senescence in primary cell cultures (Kondoh et al, 2005). Increased ribose phosphate generation from phosphoglycerate mutase uncouples glycolysis from ATP formation in proliferating cells (Vander Heiden et al, 2010). Pyruvate not oxidized through the Krebs cycle generates citrate through pyruvate carboxylase and which is used by ATP citrate lyase to generate acetylCoA for lipogenesis .…”

Characterization of HIF‐1α/Glycolysis Hyperactive Cell Population via Small‐Molecule‐Based Imaging of Mitochondrial Transporter Activity

“…Aerobic glycolysis is the basic metabolic characteristic of cancer cells, and has profound effects on cancer cell proliferation, biosynthesis and the initial stages of tumorigenesis 7. Recently, hyperactive glycolysis was found to be the preferred metabolic program in cancer cells and was regarded as the fundamental factors leading to the promotion of CSC self‐renewal and undifferentiation 8.…”