Description du sujet de thèse

The small G protein Arf6 is involved in intracellular trafficking, and particularly in the endocytosis/recycling of membrane receptors(1). It also plays an essential role in the establishment of epithelial polarity, notably in the assembly of tight junctions and their anchoring in the acto-myosin ring(2). however the different effectors and molecular mechanisms involved in these processes are still poorly understood.
SUMOylation is a post-translational modification involving the covalent but reversible conjugation of an 11-kDa polypeptide called Small Ubiquitin like Modifier (SUMO) to specific lysine residues of substrate proteins(3). Molecularly, SUMOylation can modulate the dynamics of multi-protein complexes by preventing the interaction of the modified protein with its usual protein partners, or by providing new binding sites for new interactions. SUMOylation is known to be involved in endocytosis pathways and cellular architecture(3) , but here again the mechanisms and substrates remain poorly characterized.
By immunoprecipitation and mass spectrometry analysis, we discovered, in close collaboration with Dr. S. Martin's team (IPMC), that Arf6 protein was SUMOylated in vivo. We have succeeded in producing the Arf6 protein in vitro in a prokaryotic system and purifying it in its SUMOylated form. This will enable us to study its biochemical properties. Finally, we have identified two lysines as major SUMOylation sites. This will enable us to produce mutants that are no longer SUMOylable, in order to study the consequences of the absence of Arf6 SUMOylation.
The aim of the proposed project is to understand the functional consequences of Arf6 SUMOylation through biochemical and cell biology studies
1. D'Souza-Schorey, C., and Chavrier, P. (2006) ARF proteins: roles in membrane traffic and beyond. Nat Rev Mol Cell Biol 7, 347-358
2. Klein, S., Partisani, M., Franco, M., and Luton, F. (2008) EFA6 facilitates the assembly of the tight junction by coordinating an Arf6-dependent and -independent pathway. J Biol Chem 283, 30129-30138
3. Schorova, L., and Martin, S. (2016) Sumoylation in Synaptic Function and Dysfunction. Frontiers in synaptic neuroscience 8, 9

Contexte de travail

The position is funded by the ANR. The project is headed by Michel Franco. Our team belongs to the Institut de Pharmacologie Moléculaire et Cellulaire (www.ipmc.cnrs.fr), a joint public research institute of the CNRS, INSERM and the Université Côte d'Azur. The Institute is located in Sophia Antipolis, a technology park near Antibes and Nice. Candidate profile: Master's degree or equivalent in: biology or biochemistry, engineering.