Our work is at a point of overlap between developmental biology (the development of the wing in the fly, Drosophila melanogaster) and two major themes in cellular biology: signal transduction (of the morphogenic and oncogenic Hedgehog signal, HH) and intracellular trafficking of proteins. Our aim is to elucidate the mechanisms involved and to integrate these events in a cellular and developmental context.
HH is involved in many developmental processes in animals and numerous carcinomas are associated with HH pathway deregulation. HH signal reception and transduction relies on two transmembrane proteins, Patched (Ptc) and Smoothened factor called Cubitus interruptus (Ci)/GLI. Using high-throughput two-hybrid screens (collaboration with Hybrigenics), we previously identified novel interactions and interactors. We are currently using genetic, molecular and cellular techniques (in cultured cells and in flies) to study the role of three of these interactors. We thus hope to get a better understanding of HH transduction in Drosophila and, given the conservation of this pathway, also in Human – especially as concerns oncogenic pathologies.
(i) Findings from our and other studies highlight the importance of membrane protein trafficking in the control of the HH pathway and in establishing the HH morphogenetic gradient. We want to determine in more detail the relationships between protein interactions, intracellular trafficking and post-translational changes involved in the transduction of the HH signal. We also intend to investigate how these various processes are regulated to produce different dose-dependent responses to HH. We are therefore characterizing novel phosphorylations of Smo and studying the ubiquitination of Ptc by two related ubiquitin-ligases of the NEDD4 family.
(ii) Our second project aims to provide a better understanding of the Ubiquitin-dependent processes that control the fate of Ci/GLI. We are studying the effect of a novel protein on the choice between degradation and cleavage of the transcription factor Ci.
(iii) Finally, in collaboration with Dr. R. Homlgren (Northwestern) we are seeking novel partners of HH signalling by combining the results of our two-hybrid screens with a genetic screen. We plan to complement these screens with a proteomic analysis of the proteins for which ubiquitination is regulated by HH.