RhoGDI2, why can’t you be more like your brother? The role of RhoGDI2 and RhoGDI1 in cancer biology

1. Background
RhoGTPases contribute to cancerogenesis due to their involvement in various signaling pathways. This has garnered attention towards their key regulators, among which are three RhoGDIs (Rho protein-guanine dissociation inhibitors). Recent research demonstrates that RhoGDI 1 and 2 differ in their functions and that RhoGDI2 has dual pro- and anti-tumor properties, making it a valuable target to decipher the different intertwined mechanisms regulating cancer progression.
2. Aim
This study aims to enhance our understanding of the specific role of RhoGDI2, notably by exploring how and why it acts differently compared to RhoGDI1.
3. Methods
 Prostate adenocarcinoma (PC3), osteosarcoma (U2OS) and retinal pigment epithelial (RPE-1) cells are used as exploratory models to observe how various phenotypes are modified upon RhoGDI2/RhoGDI1 silencing.
 BioID, a novel proximity-dependent labelling system, will be used to identify yet to be discovered binding partners of RhoGDI2.
 Generation and characterization of PC3 and U2OS cells conditionally overexpressing either recombinant RhoGDI1 or RhoGDI2, or chimeric RhoGDIs resulting from swapping their N-terminal ends.
4. Results
 RhoGDI2 silencing significantly diminished proliferation in U2OS, PC3 and RPE-1 cell lines compared to RhoGDI1 silencing and control siRNA.
 RhoGDI2 silencing induced abnormal centrosomal amplification.
 A 2-fold decrease in the number of RPE-1 cells harboring a primary cilium (anchoring on the centrosome) was observed after RhoGDI2 silencing as compared to cells with RhoGDI1 silencing and control siRNA.
 With a classical IP/MS, we shortlisted potential RhoGDI2 interactors which will be validated via BioID.
 Preliminary experiments using PC3 cells expressing recombinant or chimeric RhoGDIs suggest a specific role of the N-terminal domain of RhoGDI2 in the regulation of cell proliferation.
5. Conclusion
The required tools have been generated and further experiments will enable us to understand why RhoGDI2 behaves differently than RhoGDI1 in context of cancer biology.