Mécanismes moléculaires qui sous-tendent la fonction de la protéine PLD2 au niveau de la biogénèse des exosomes
Lipid membranes act as selective barriers for signal transduction pathways and also constitute a source of lipids participating in various signaling events. Lipid composition of the membrane changes upon the action of lipid modifying enzymes. Thereby, the signal is transmitted inside cellular compartments. We have shown that the production of phosphatidylinositol 4,5-bisphosphate (PIP2) on endosomes, under the control of ADP ribosylation factor 6 (ARF6) and its effector phosphatidylinositol 4-phosphate 5-kinase (PIP5K), mediates the recycling of endocytosed proteins to the plasma membrane* and impact on Wnt signaling, most probably in a cell autonomous manner. We showed that this process is orchestrated by sequential peptide and lipid binding by the PDZ domains of syntenin, a small adaptor protein. ARF6 is also controlling the budding of endosomes to form multivesicular bodies (MVBs) that will liberate exosomes**. This alternative pathway also involves the ARF6 but another effector, namely phospholipase D2 (PLD2) and orchestrate non cell autonomous signaling. Indeed, exosomes emerge as important players in cell-cell communication (including in various systemic diseases) because they can transport specific bioactive molecules including nucleic acids to reprogram recipient cells. This project aims to contribute to our understanding of the roles of syntenin and phosphatidic acid (the product of PLD2) in exosome biogenesis and activity. The research will provide fundamental new knowledge to pave the way for the rational design of syntenin chemical inhibitors. Such compounds will be of potential therapeutic value in "exosome-sustained/systemic" diseases. During this training, the student will have a chance to learn techniques such as cell culture, gain and loss-of-function assays, purification of exosomes, characterization of protein extracts by Western-blot, nanoparticle tracking analysis, site-directed mutagenesis and confocal microscopy.
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