Our main focus is to investigate how the critical regulators of Rho activity, the RhoGEF and RhoGAP proteins (with 145 genes in human), impart specificity to Rho signaling by providing contextual information. We therefore exploit a unique RhoGEF/GAP cDNA expression library that we have previously assembled and corresponding data from a family-wide functional analysis of these regulatory proteins. We use this resource both for systems-level studies and the characterization of novel individual regulators in different functional contexts. Our second goal is to explore at the single molecule level how Rho GTPases (and associated proteins) dynamically distribute between cell membranes. We aim to understand how Rho signaling complexes are formed, maintained and disassembled and how the Rho GDP/GTP reaction cycle is coupled to the Rho membrane association cycle. Our research provides important organization principles of the Rho signaling system and thereby will advance our understanding of the regulation of cell shape in physiological and disease processes.
Rho family GTPase proteins are the master regulators of the cytoskeleton, controlling fundamental morphogenetic processes ranging from embryonic development to wound repair. We investigate how the signaling function of Rho GTPases is regulated in space and time and how its specificity is achieved.
Rho activity is controlled by three factors: GTPase activating proteins (RhoGAPs) and guanine nucleotide exchange factors (RhoGEFs), which drive the GDP/GTP activity cycle, and guanine nucleotide dissociation inhibitors (GDIs), which keep the lipid-anchored GTPases in the cytosol. Our genome encodes as many as 145 RhoGEFs and GAPs. These multi-domain proteins can target the GTPases to distinct cellular locations and act as scaffolds to connect to upstream cues, further signaling programs and downstream effectors.
We have previously assembled a complete cDNA library of all RhoGEFs and GAPs and performed a systematic analysis of their interactors, localization and substrate specificities. Combining advanced microscopy with cell biology and work in model organisms, we now exploit this unique dataset and toolbox to characterize novel RhoGEFs and GAPs in different signaling contexts. These currently include: control of cell-cell adhesion, guidance receptor and G protein coupled receptor signaling, with implications in muscle development, endocrine signaling and neural cancer development.
Another research interest is to analyze the membrane interaction dynamics of the lipid-anchored Rho proteins and how it is regulated. How on membranes Rho signaling complexes are formed, maintained and disassembled is not well studied. We use state-of-the-art imaging to elucidate such modes of temporal Rho signal regulation.