Biology subjects

Cook, K. M.

Publications and source records attributed to Cook, K. M..

3 recordsLinked to original sources

bioRxiv2021

Intermittent hypoxia enhances the expression of HIF1A by increasing the quantity and catalytic activity of KDM4A-C and demethylating H3K9me3 at the HIF1A locus

Cellular oxygen-sensing pathways are primarily regulated by hypoxia inducible factor-1 (HIF-1) in chronic hypoxia and are well studied. Intermittent hypoxia also occurs in many pathological conditions, yet little is known about its biological effects. In this study, we investigated how two proposed cellular oxygen sensing systems, HIF-1 and KDM4A-C, respond to cells exposed to intermittent hypoxia and compared to chronic hypoxia. We found that intermittent hypoxia increases HIF-1 activity through a pathway distinct from chronic hypoxia, involving the KDM4A, -B and -C histone lysine demethylases. Intermittent hypoxia increases the quantity and activity of KDM4A-C resulting in a decrease in H3K9 methylation. This contrasts with chronic hypoxia, which decreases KDM4A-C activity, leading to hypermethylation of H3K9. Demethylation of histones bound to the HIF1A gene in intermittent hypoxia increases HIF1A mRNA expression, which has the downstream effect of increasing overall HIF-1 activity and expression of HIF target genes. This study highlights how multiple oxygen-sensing pathways can interact to regulate and fine tune the cellular hypoxic response depending on the period and length of hypoxia.

cell biology↗

bioRxiv2019

C-terminal HSP90 Inhibitors Block the HSP90:HIF-1a Interaction and Inhibit the Cellular Hypoxic Response

Hypoxia Inducible Factor (HIF) is a transcription factor activated by low oxygen, which is common in solid tumours. HIF controls the expression of genes involved in angiogenesis, chemotherapy resistance and metastasis. The chaperone HSP90 (Heat Shock Protein 90) stabilizes the subunit HIF-1 and prevents degradation. Previously identified HSP90 inhibitors bind to the N-terminal pocket of HSP90 which blocks binding to HIF-1, and produces HIF-1 degradation. N-terminal inhibitors have failed in the clinic as single therapy treatments due in part because they induce a heat shock response, which increases chemotherapy resistance. SM molecules are HSP90 inhibitors that bind to the C-terminus and do not activate the heat shock response. The effects of C-terminal HSP90 inhibitors on HIF-1 are unreported. Herein we show that SM compounds block binding between HSP90 and HIF-1, leading to HIF-1 degradation through the proteasome using the PHD/pVHL pathway in hypoxic conditions. The SM compounds decrease HIF-1 target gene expression at the mRNA and protein level under hypoxia in colorectal cancer cells, leading to cell death, without inducing a heat shock response. Our results suggest that targeting the C-terminus of HSP90 blocks the hypoxic response and may be an effective anti-cancer strategy.

cancer biology↗

bioRxiv2019

Evaluation of a potential redox switch in blood coagulation tenase

Blood coagulation factor IXa (FIXa) activates factor X that leads to thrombin and fibrin formation and a stable thrombus. FIXa catalytic efficiency is markedly enhanced when bound to the co-factor, factor VIII (FVIII), and a negatively charged phospholipid surface in the tenase complex. Small redox active peptides and protein oxidoreductases have been shown previously to have some FIXa co-factor activity and thiol modifying agents have been reported to influence FVIII activity. These observations suggested that FIXa might contain an allosteric disulfide that is regulated by FVIII. This idea was tested by measuring the influence of FVIII on the redox state of FIXa disulfide bonds and the effect of plasma oxidoreductases on FIXa activity. The redox state of nine of the 11 disulfide bonds in FIXa was measured using differential cysteine labelling and mass spectrometry and all were oxidized in the protein, and this did not change upon binding of the enzyme to FVIII. All eight disulfide bonds in FVIII were also predominantly oxidized and this did not appreciably change upon FIXa binding. In addition, relevant protein reductants in the circulation inhibited rather than activated FIXa activity. In conclusion, we found no evidence that the co-factor function of FVIII involves a change in the redox state of one or more FIXa disulfide bonds.

biochemistry↗