Small Ubiquitin-related Modifier (SUMO)-1 Promotes Glycolysis in Hypoxia

Abstract

Under conditions of hypoxia, most eukaryotic cells undergo a shift in metabolic strategy, which involves increased flux through the glycolytic pathway. Although this is critical for bioenergetic homeostasis, the underlying mechanisms have remained incompletely understood. Here, we report that the induction of hypoxia-induced glycolysis is retained in cells when gene transcription or protein synthesis are inhibited suggesting the involvement of additional post-translational mechanisms. Post-translational protein modification by the small ubiquitin related modifier-1 (SUMO-1) is induced in hypoxia and mass spectrometric analysis using yeast cells expressing tap-tagged Smt3 (the yeast homolog of mammalian SUMO) revealed hypoxia-dependent modification of a number of key glycolytic enzymes. Overexpression of SUMO-1 in mammalian cancer cells resulted in increased hypoxia-induced glycolysis and resistance to hypoxia-dependent ATP depletion. Supporting this, non-transformed cells also demonstrated increased glucose uptake upon SUMO-1 overexpression. Conversely, cells overexpressing the de-SUMOylating enzyme SENP-2 failed to demonstrate hypoxia-induced glycolysis. SUMO-1 overexpressing cells demonstrated focal clustering of glycolytic enzymes in response to hypoxia leading us to hypothesize a role for SUMOylation in promoting spatial re-organization of the glycolytic pathway. In summary, we hypothesize that SUMO modification of key metabolic enzymes plays an important role in shifting cellular metabolic strategies toward increased flux through the glycolytic pathway during periods of hypoxic stress.In the steady state (when oxygen levels within a cell exceed bioenergetic requirements), activity of the glycolytic pathway, the TCA (tricarboxyic acid) cycle and electron transport chain combine to generate ϳ38 molecules of adenosine triphosphate (ATP) per molecule of glucose metabolized. Glycolysis and the TCA cycle each generate 2 molecules of ATP with the remaining 34 molecules being produced during oxidative phosphorylation. This process provides the ATP necessary to maintain physiologic function. However, under conditions where oxygen demand exceeds supply (hypoxia), most cells retain the capacity to fundamentally shift metabolic strategy to a state where mitochondrial activity is decreased and glycolysis becomes the primary pathway for ATP generation (1). Normally, this metabolic switch promotes cell survival during hypoxia and is thus adaptive in nature. In such cases, cells switch back to the predominantly oxidative metabolism when the oxygen balance is restored. This phenomenon is known as the Pasteur effect (3). Alternatively, in the hypoxic compartment of a growing tumor, which has outgrown the local blood supply, the ability of cells to develop enhanced glycolytic metabolism confers a survival advantage for the tumor. Furthermore, some cancer cells develop the ability to maintain enhanced glycolysis even when sufficient oxygen supply returns, a phenomenon known as the Warburg effect (35). Thus, the ability of cell...

Deciphering the emerging role of SUMO conjugation in the hypoxia-signaling cascade

“…Hypoxia-induced transcription of SUMO1 or R WD-containing SUM Oylation enhancer (RSUME) might explain the global effects on SUMOylation by directly targeting the conjugation machinery (Comerford et al , 2003 ;Shao et al , 2004 ;Carbia -Nagashima et al, 2007 ), while regulation of specific SUMO E3 ligases, such as PIAS4, might account for more restricted effects . Furthermore, SUMO1 overexpression has been related with an increase in glycolysis and glucose uptake (Agbor et al , 2011 ). It has been proposed that SUMO could play a role in the metabolic switch to glycolysis, contributing to the cellular adaptation to hypoxia, which is consistent with the fact that GLUT-1 and GLUT-4 are substrates for SUMO (Giorgino et al , 2000 ).…”

EAF2 Suppresses Hypoxia-Induced Factor 1α Transcriptional Activity by Disrupting Its Interaction with Coactivator CBP/p300

“…In this study, we showed that EAF2 modulated the induction of several cellular glucose metabolismrelated genes downstream of HIF-1␣, such as SLC2A (Glut-1), PDK-1, and LDHA. Thus, we investigated whether EAF2 can also affect cellular glucose metabolism by measuring cellular glucose uptake in the presence or absence of EAF2 with a Biovision glucose uptake assay kit, as employed by previous investigators, following the protocol provided by the manufacturer (15,35,36). Under hypoxic conditions, EAF2…”

NFκB and HIF display synergistic behaviour during hypoxic inflammation

“…Whole-cell, nuclear and cytosolic extracts were generated in either normoxia or hypoxia according to previously published protocols [30,31]. Protein concentration was quantified using a Bradford assay, and samples were normalised accordingly.…”

“…Protein concentration was quantified using a Bradford assay, and samples were normalised accordingly. Samples were separated by SDS-PAGE and immunoblotted as described previously [30,31] using the following primary Abs and dilutions: HIF-1# (1:250; BD Pharmingen), "-actin (1:10,000; Sigma) and TATA box binding protein (TBP; 1:2500; Abcam).…”