Resolving the dynamics of spatially distinct RhoB signaling networks in breast epithelial cells

• Applicant: Professorin Dr. Monilola Afolabi Olayioye
• Subject Area: Cell Biology
• Term: since 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 376941317

The Rho GTPase subfamily comprising the members RhoA, RhoB, and RhoC are key regulators of the actin and microtubule cytoskeleton whereby cell morphology and polarity, and organelle positioning within the cell are maintained. Unlike RhoA and RhoC, which primarily localize at the plasma membrane, RhoB additionally associates with endomembranes where it regulates membrane trafficking. Interestingly, while RhoB signaling from the plasma membrane has been linked to oncogenic functions, signaling from endomembranes is thought to be tumor-suppressive. Despite these intriguing observations there is still limited knowledge about the signaling networks controlling these different subcellular RhoB pools. In the first funding period, we identified the RhoGEF protein Solo as a positive regulator of endosomal RhoB. Here we will explore how Solo and GEF-H1, a previously characterized regulator of RhoB, control spatial RhoB signaling. To this end, we will first make use of state-of-the-art genome editing techniques to enable, for the first time, the visualization of the endogenous RhoB protein in living cells. By quantitative live imaging we will derive unprecedented insights into the dynamics of RhoB and its spatial regulation by Solo and GEF-H1. We will further employ optogenetic manipulations to discern the molecular networks that govern RhoB function at different cellular locations. Because RhoB and its regulators are differentially expressed in epithelial versus mesenchymal cells, we postulate that the cellular differentiation state is a critical factor in determining RhoB function. Exploring the cell state-dependent, spatially distinct RhoB dynamics and signaling is crucial for understanding the complex role that RhoB plays in normal physiological processes and in neoplastic cell transformation.

• DFG Programme: Research Grants
• Co-Investigator: Professorin Dr. Angelika Hausser