SGK3 activity and regulation in PI3K-Akt pathway inhibitor resistance in breast cancer
type: CreativeWork
description: The PI3K-Akt signalling pathway is central to cell proliferation and growth, and hyperactivating mutations in this pathway are found in a large number of cancers. Downstream of PI3K, Akt is heavily studied, however the highly related SGK family of protein kinases have recently been identified as driving cancer cell growth in certain contexts. In particular, my research interest and the focus of this thesis is the role these kinases, in particular SGK3, has in resistance to Class I PI3K and Akt inhibitors in certain ER+ breast cancers. The first major aim of my PhD was to develop a method by which the signalling of SGK3 can be specifically modulated in cancer cells. Due to the high homology between the SGK family of protein kinases, chemical inhibition of SGK3 specifically has not been possible. Further, model cancer cell lines have been intractable to genome modification. I therefore, in collaboration with the Ciulli lab, designed and characterised SGK3-PROTAC1, a Proteolysis Targeting Chimera (PROTAC) which targeted SGK3 for specific ubiquitylation by VHL E3 ligase and subsequent proteasomal degradation. I demonstrated by quantitative Mass Spectrometry that SGK3-PROTAC1 mediated degradation was highly specific. Rapid, reversible degradation of SGK3 provided a tool for specifically modulating SGK3 in cancer cells. Further analysis using this compound in ZR-75-1 cells suggested some possible, previously unknown functions of SGK3 in cAMP signalling and mitochondrial metabolism. On degradation of SGK3, I observed a downregulation of the phosphodiesterase PDE4D and upregulation of a host of proteins mediating Oxidative Phosphorylation in mitochondria. These effects were observed only on degradation of the protein and not inhibition of its kinase activity, suggesting putative kinase-independent roles of SGK3. These findings would be extremely exciting to follow up in future work, and demonstrate the power of the PROTAC approach. Given the potential of the PROTAC approach…
abstract: The PI3K-Akt signalling pathway is central to cell proliferation and growth, and hyperactivating mutations in this pathway are found in a large number of cancers. Downstream of PI3K, Akt is heavily studied, however the highly related SGK family of protein kinases have recently been identified as driving cancer cell growth in certain contexts. In particular, my research interest and the focus of this thesis is the role these kinases, in particular SGK3, has in resistance to Class I PI3K and Akt inhibitors in certain ER+ breast cancers. The first major aim of my PhD was to develop a method by which the signalling of SGK3 can be specifically modulated in cancer cells. Due to the high homology between the SGK family of protein kinases, chemical inhibition of SGK3 specifically has not been possible. Further, model cancer cell lines have been intractable to genome modification. I therefore, in collaboration with the Ciulli lab, designed and characterised SGK3-PROTAC1, a Proteolysis Targeting Chimera (PROTAC) which targeted SGK3 for specific ubiquitylation by VHL E3 ligase and subsequent proteasomal degradation. I demonstrated by quantitative Mass Spectrometry that SGK3-PROTAC1 mediated degradation was highly specific. Rapid, reversible degradation of SGK3 provided a tool for specifically modulating SGK3 in cancer cells. Further analysis using this compound in ZR-75-1 cells suggested some possible, previously unknown functions of SGK3 in cAMP signalling and mitochondrial metabolism. On degradation of SGK3, I observed a downregulation of the phosphodiesterase PDE4D and upregulation of a host of proteins mediating Oxidative Phosphorylation in mitochondria. These effects were observed only on degradation of the protein and not inhibition of its kinase activity, suggesting putative kinase-independent roles of SGK3. These findings would be extremely exciting to follow up in future work, and demonstrate the power of the PROTAC approach. Given the potential of the PROTAC approach…
author: Tovell, Hannah
language: eng
date published: 2020
date modified: 2026-07-24T02:08:52Z
provider: University of Dundee
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Dundee