eprintid: 10041064
rev_number: 27
eprint_status: archive
userid: 608
dir: disk0/10/04/10/64
datestamp: 2018-02-09 12:25:54
lastmod: 2021-02-01 07:10:10
status_changed: 2018-02-09 12:25:54
type: thesis
metadata_visibility: show
creators_name: Grimm, Fiona
title: Mechanisms of cellular metabolic regulation in short-term hypoxia
ispublished: unpub
divisions: UCL
divisions: A01
divisions: B02
divisions: C08
abstract: In tumours, cell proliferation and inefficient perfusion lead to transient and chronic fluctuations of oxygen supply, causing localised hypoxia. A key mechanism for survival in hypoxia is the reprogramming of cellular metabolism, which current evidence suggests is primarily mediated at the transcriptional level by HIF1α. This work demonstrates that well-known, hypoxia-associated metabolic changes, such as increased glycolysis and lactate production, occur within only 3-5 hours at 1% O₂ in a HIF1α-independent manner. Concomitant to these changes, intracellular aspartate levels decline, partly through decreased mitochondrial aspartate production, implying altered activity of the mitochondrial malate-aspartate shuttle (MAS). Pharmacological and genetic ablation experiments demonstrated that aspartate aminotransferase 1 (GOT1), a component of the MAS, is necessary for upregulation of glycolysis in early hypoxia. Loss of GOT1 also limited flux through cytoplasmic redox pathways and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and decreased the cytoplasmic NAD⁺/NADH ratio, suggesting that multiple redox systems collectively account for early hypoxia-induced metabolic changes. Furthermore, lactate dehydrogenase (LDHA) loss of function had a strong inhibitory effect on glycolytic flux, caused increased respiration and dependency on OXPHOS-derived ATP, and diversion of glucose carbons into the TCA cycle and fatty acid biosynthesis. In early hypoxia, LDHA knockout cells exhibited ATP depletion and AMPK activation and proliferation was inhibited irreversibly, indicating an important function of LDHA in maintaining ATP levels and regulating glucose carbon fate to ensure cell survival. In summary, this work reveals that key features of the cellular metabolic response to hypoxia are established early, prior to the onset of protein expression changes. These changes are orchestrated by a nexus of redox pathways to maintain cellular bioenergetics and cell survival. In addition, this work highlights metabolic vulnerabilities of cells in hypoxia, that could potentially be exploited for cancer therapy.
date: 2018-01-28
date_type: published
oa_status: green
full_text_type: other
thesis_class: doctoral_open
thesis_award: Ph.D
language: eng
thesis_view: UCL_Thesis
primo: open
primo_central: open_green
verified: verified_manual
elements_id: 1523415
lyricists_name: Grimm, Fiona
lyricists_id: FGRIM64
actors_name: Grimm, Fiona
actors_id: FGRIM64
actors_role: owner
full_text_status: public
pagerange: 1-226
pages: 226
event_title: University College London
institution: UCL (University College London)
department: Division of Biosciences
thesis_type: Doctoral
editors_name: Anastasiou, D
citation:        Grimm, Fiona;      (2018)    Mechanisms of cellular metabolic regulation in short-term hypoxia.                   Doctoral thesis  (Ph.D), UCL (University College London).     Green open access   
 
document_url: https://discovery-pp.ucl.ac.uk/id/eprint/10041064/1/FionaGrimm_thesis_corrected.pdf