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Title: The role of ERK5 in HeLa cells and endothelial cells
Author: Alrumayh, A. M.
ISNI:       0000 0004 8505 5835
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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Extracellular regulated signal protein kinase 1/2 and 5 (ERK1/2 and ERK5) are members of the MAPK family which are involved in cellular proliferation, differentiation, migration. ERK5, the most recently discover MAPK, differs in that contains a large carboxyl-terminal tail. Various growth factors and cellular stresses are able to activate ERK5 and its physiological importance was displayed following erk5 gene ablation in mice, where resulted in embryonic lethality around E9.5-11.5. ERK1/2 was the first MAPK to be discovered and it is also activated by a host of stimuli. Aberrant signalling involving either ERK1/2 or ERK5 has been reported in various cancers including breast, cervical, hepatocellular and melanoma. This study investigated the differences in ERK5 activation and its influence on ERK1/2 in both EGF stimulated HeLa cells (an immortalised epithelial cervical cancer cell line) and VEGF stimulated primary human dermal microvascular endothelial cells (HDMECs). It was revealed that VEGF has the ability to induce the dual phosphorylation of the kinase domain of ERK5, without any effect on the phosphorylation of the C-terminal residues. Results obtained using a Phos-tag™ reagent in SDS-PAGE suggested that phosphorylation of Thr218/Tyr220 in the kinase domain and C-terminal phosphorylation are not mutually inclusive events and that ERK5 can be activated in the absence of C-terminal phosphorylation. On the other hand, EGF stimulated HeLa cells led to phosphorylation of ERK5 on Thr218/Tyr220 as well causing the nuclear translocation of ERK5. The analysis of intracellular signalling pathways after treatment with trametinib and selumetinib which inhibit ERK1/2 caused the activation of ERK5 in HeLa cells, suggesting that pharmacological inhibition of ERK1/2 can result in activation of ERK5. This project also investigated the role of ERK5 in drug resistance using a HeLa resistant cell line with acquired resistance to trametinib. It was shown that inhibition of MEK5/ERK5 signalling pathway by BIX02189 increased the sensitivity of HeLa cells to trametininb. These trametinib resistant HeLa cells also show reactivation of ERK1/2 and a small activation of ERK5 but did not appear to upregulate MEKK2/MEKK3, MEK5, ERK5 expression. In summary, this project has proposed that the ERK5 signalling pathway is a feasible therapeutic target for drug resistance in cancer.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral