Internship

Role of synaptotagmin association with gangliosides in synaptotagmin/SV2 association

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The project addresses the characterization of a newly uncovered ganglioside / synaptotagmin interaction that takes place between gangliosides (residents of the plasma membrane external leaflet) and a domain of the synaptic vesicle protein synaptotagmin that transiently becomes accessible to the extracellular space during neurotransmitter release.

Description

The exo-endocytotic cycle of synaptic vesicles is a hallmark of neuronal synaptic terminals. A dynamic molecular interplay takes place between compartmentalized proteins and lipid molecules during synaptic vesicle fusion and fission.
Lipids are essential components of the exo-endocytic machinery of neurotransmitter release. They are involved in crucial steps such as vesicle recruitment, membrane organization and deformation, fusion of secretory vesicles with plasma membranes, endocytosis as well as recycling.
In synapses, lipids such as cholesterol, sphingosine, phosphatidic acid or phosphoinositides of the inner plasma membrane leaflet affect the spatial distribution and/or function of proteins essential for neurotransmitter release (1, 2, 3), such as the SNARE proteins syntaxin1, SNAP-25 and VAMP2 or also the principal calcium-sensor for exocytosis synaptotagmin at nerve terminals. However, outer plasma membrane leaflet lipid interactions with freshly exocytosed protein domains are not a well-investigated area and whether these interactions impact physiological processes has not been adequately addressed.
We recently discovered that upon exocytosis, the intra-vesicular domain of synaptotagmin that is transiently expressed at the neuronal surface directly interacts with extra-leaflet glycosphingolipids and that this interaction, of unknown physiological significance, has structural consequences on synaptotagmin (4). Synaptotagmin is a transmembrane protein, abundantly expressed in synaptic vesicles and neurosecretory granules. It interacts with and its traffic is regulated by the synaptic vesicle protein SV2 that is a target for Levetiracetam, an anti-epileptic drug.

In this project we will address the potential influence of synaptotagmin / glycosphingolipids interaction on synaptotamin / SV2 complex formation.

1. Tanguy, E., Wang, Q., Moine, H. & Vitale, N. Phosphatidic Acid: From Pleiotropic Functions to Neuronal Pathology. Front Cell Neurosci 13, 2, doi:10.3389/fncel.2019.00002 (2019).

2.Ammar, M. R., Kassas, N., Chasserot-Golaz, S., Bader, M. F. & Vitale, N. Lipids in Regulated Exocytosis: What are They Doing? Front Endocrinol (Lausanne) 4, 125, doi:10.3389/fendo.2013.00125 (2013).

3. Garcia-Martinez, V. et al. Emerging evidence for the modulation of exocytosis by signalling lipids. FEBS Lett 592, 3493-3503, doi:10.1002/1873-3468.13178 (2018).

4. Flores, A. et al. Gangliosides interact with synaptotagmin to form the high-affinity receptor complex for botulinum neurotoxin B. Proc Natl Acad Sci U S A 116, 18098-18108, doi:10.1073/pnas.1908051116 (2019).

Desired profile

The candidate must be interested in molecular neurobiology and have a minimal theoretical background in neuron biology and neurotransmission mechanisms. The candidate will use several approaches allowing protein-protein as well as protein-lipid interaction studies (Langmuir monolayers, optical biosensors, immunoprecipitations). The candidate will also use cell cultures and will participate in cloning procedures to generate cDNA constructs encoding mutant and wild type proteins.

Host institution

The team is part of the laboratory of Neurobiology of Ion channels in Marseille (UMR S_1072). In this laboratory, neuronal communication is Investigated at different levels covering neuronal protein-protein as well as protein-lipid interaction and electrophysiological analysis of neuronal excitability and communication.

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