Abstract
RhoJ is a member of the Rho GTPase family of signalling proteins that is highly expressed in endothelial cells and regulates cell shape and polarity. RhoJ also regulates tumour angiogenesis which makes it a potential therapeutic target. Previous work in our lab demonstrated that RhoJ controls the intracellular trafficking of two important proteins during angiogenesis: podocalyxin and integrin α5β1. The initial aim of this project focused on applying an unbiased screening approach to identify additional potential cargos of RhoJ.I used surface biotinylation and quantitative mass spectrometry to identify surface proteins that were regulated by RhoJ in endothelial cells. The surface expression of Tie2, a receptor tyrosine kinase that is also highly expressed in endothelial cells, was shown to be regulated by RhoJ. Moreover, with stimulation of its ligand Ang1, the trafficking and the downstream signalling of Tie2 were shown to be controlled by RhoJ in confluent endothelial cells.
The Ang1/Tie2 axis regulates endothelial permeability. I found that the expression of a constitutively active RhoJ-QL mutant increased a baseline level of endothelial permeability. Further investigation showed that this regulation was independent of Ang1/Tie2. Moreover, active RhoJ-QL mutant led to the disorganised expression of junctional proteins. Including VE-cadherin and PECAM-1, in resting endothelial cells. Transduction of RhoJ-QL resulted in decreased myosin light chain phosphorylation and decreased cortical actin at the same time.
In summary, the work presented in this thesis demonstrates novel regulatory roles of RhoJ in quiescent but not angiogenic endothelial cells, including the regulation of the Ang1/Tie2 axis and cell junctions.
| Date of Award | 3 Oct 2023 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Harry H Mellor (Supervisor) & Jon D Lane (Supervisor) |
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