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Glycolytic Enzyme Coalesce in G bodies Under Hypoxic Stress

ABSTRACT: Glycolysis is upregulated in cells under specific conditions, such as hypoxia and high energy demand, to achieve the metabolic requirements for continued cell proliferation. However, the mechanism of this increased glycolytic rate remains poorly understood. In the budding yeast Saccharomyces cerevisiae, we discovered that hypoxia induces concentration of many glycolytic enzymes, including the Pfk2p subunit of the ratelimiting enzyme, phosphofructokinase, into a single, non-membrane-bound granule that we define as the "glycolytic body" or "G body". Pfk2p localization to G bodies depends on its N-terminal, intrinsically disordered region. In order to identify factors important for G body formation, we conducted a yeast kinome screen and identified the AMP kinase ortholog, Snf1p, to be required for the localization of multiple glycolytic enzymes to G bodies. Further, proteomic analyses of purified G bodies identified a core set of resident factors, many of which are essential for G body integrity. Cells incapable of forming G bodies in hypoxic conditions display abnormal cell division and produce inviable daughter cells. Conversely, cells that form G bodies show increased glucose consumption and decreased levels of glycolytic intermediates. Importantly, G bodies also form in human, hepatocarcinoma cells upon hypoxic stress. Together, our results suggest that G body formation is a conserved, adaptive response to increase glycolytic output during hypoxia or tumorigenesis.

INSTRUMENT(S): LTQ Orbitrap Velos

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

TISSUE(S): Diploid Cell

DISEASE(S): Disease Free

SUBMITTER: John Kim

LAB HEAD: John K. Kim

PROVIDER: PXD006686 | Pride | 2017-07-24

REPOSITORIES: Pride

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Project description:Background: A significant body of evidence accumulated over the last century suggests a link between hypoxic microenvironments within the infected host and the latent phase of tuberculosis. Studies to test this correlation have identified the M. tuberculosis initial hypoxic response, controlled by the two-component response regulator DosR. The initial hypoxic response is completely blocked in a dosR deletion mutant. Methodology/Principal Findings: We show here that a dosR deletion mutant enters bacteriostasis in response to in vitro hypoxia with only a relatively mild decrease in viability. In the murine infection model, the phenotype of the mutant was indistinguishable from that of the parent strain. These results suggested that additional genes may be essential for entry into and maintenance of bacteriostasis. Detailed microarray analysis of oxygen starved cultures revealed that DosR regulon induction is transient, with induction of nearly half the genes returning to baseline within 24 hours. In addition, a larger, sustained wave of gene expression follows the DosR-mediated initial hypoxic response. This Enduring Hypoxic Response (EHR) consists of 230 genes significantly induced at four and seven days of hypoxia but not at initial time points. These genes include a surprising number of transcriptional regulators that could control the program of bacteriostasis. We found that the EHR is independent of the DosR-mediated initial hypoxic response, as EHR expression is virtually unaltered in the dosR mutant. Conclusions/Significance: Our results suggest a reassessment of the role of DosR and the initial hypoxic response in MTB physiology. Instead of a primary role in survival of hypoxia induced bacteriostasis, DosR may regulate a response that is largely optional in vitro and in mouse infections. Analysis of the EHR should help elucidate the key regulatory factors and enzymatic machinery exploited by M. tuberculosis for long-term bacteriostasis in the face of oxygen deprivation. Keywords: time-course Each hypoxic timecourse compared to the matching log phase sample. Each time point/strain represented by a minimum of three replicates.

Project description:Oxygen fluctuation during tissue remodeling imposes a major metabolic challenge in human tumors. Stem-like tumor cells in glioblastomas are believed to possess extraordinary metabolic flexibility, enabling them to initiate growth even under non-permissive conditions. To identify adaptive response mechanism, we compared the effects of acute and chronic hypoxia versus oxygenation on stem-like glioblastoma (GS) cells. GS cell lines were established and propagated either under normoxia (21% O2) or hypoxia (1% O2) and subsequently exposed to acute normoxia or hypoxia, respectively. Gene expression profiling revealed that acute hypoxia predominantly induced metabolic pathways and cell cycle arrest, whereas chronic hypoxia activated neurodevelopmental processes. In particular, we found increased expression of glycolytic enzymes, especially of the preparatory phase of glycolysis, under acute hypoxia, whereas pentose phosphate pathway (PPP) enzymes were downregulated. The opposite was found for acute oxygenation of hypoxic GS cells. Findings were confirmed by qPCR and immunoblot analyses. Despite downregulation by hypoxia, expression of PPP enzymes is increased in GBMs compared to normal brain, whereas expression of hypoxia-inducible enzymes of the parallel preparatory phase of glycolysis is decreased. Immunohistochemistry revealed strong staining for PPP enzymes in the bulk of GBM tissue, especially in highly proliferative areas, but not in pseudopalisading (hypoxic) cells. Glycolytic enzymes displayed an inverse pattern. Mass spectrometric analysis using [1,2-13C2]-D-glucose showed reduced glucose flux through the PPP under hypoxia in favor of flux through glycolysis. Acute and chronic hypoxia increased cell migration but reduced proliferation, whereas normoxia had opposite effects. Our findings extend Warburg’s observations by showing that in most tumor cells the PPP, which supplies metabolites for biomass production, is favored over the parallel preparatory phase of glycolysis, but is suppressed under acute severe hypoxia, causing a switch to direct glycolysis to protect against hypoxic stress.

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Glycolytic Enzyme Coalesce in G bodies Under Hypoxic Stress

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