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2016

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Cell membrane remodeling by annexin A2 and actin: Implication in neurosecretion and nociception

Research unit

UPR 3212 - Institut des Neurosciences Cellulaires et Intégratives (INCI)
5, rue Blaise Pascal, 67084 STRASBOURG

Group

Name: Trafic membranaire dans les cellules du système nerveux

Group leader: GASMAN & VITALE Stephane & nicolas - gasman@inci-cnrs.unistra.fr vitalen@inci-cnrs.unistra.fr

Group leader's phone: 03 88 45 67 12

Group organization:
- Chercheurs: 8
- ITA: 4
- Doctorants: 4
- Post-Docs: 0
- Autres: 1

Publications of the team linked to the topic (3 last years):
1) Tryoen-Toth, P., Chasserot-Golaz, S., Tu, A., Gherib, P., Bader, M. F., Beaumelle, B., Vitale, N. HIV-1 Tat protein inhibits neurosecretion by binding to phosphatidylinositol (4,5) bisphosphate. J Cell Sci. 2013, 126:454-63.
2) Ory, S., Ceridono, M., Momboisse, F., Houy, S., Chasserot-Golaz, S., Heintz, D., Calco, V., Haeberle, A. M., Espinoza, F. A., Sims, P. J., Bailly Y., Bader, M. F., Gasman S. Phospholipid Scramblase-1-Induced Lipid Reorganization Regulates Compensatory Endocytosis in Neuroendocrine Cells. J Neurosci 2013 33: 3545-3556.
3) Ory, S., Ceridono, M., Momboisse, F., Houy, S., Chasserot-Golaz, S., Heintz, D., Calco, V., Haeberle, A. M., Espinoza, F. A., Sims, P. J., Bailly Y., Bader, M. F., Gasman S. Phospholipid Scramblase-1-Induced Lipid Reorganization Regulates Compensatory Endocytosis in Neuroendocrine Cells. J Neurosci 2013 33: 3545-3556.

About PhD

PhD Director: CHASSEROT-GOLAZ Sylvette - chasserot@unistra.fr

Phone:

Junior advisor: non

Co-tutely: non

Co-Director: non

About PhD topic :

Title: Cell membrane remodeling by annexin A2 and actin: Implication in neurosecretion and nociception

Project: The mechanisms of biological membrane remodeling are still poorly understood and elucidating them is currently a major challenge in cell biology. Defects in the composition and organization of cell membranes observed in a large number of nervous system pathologies including neuropathic pain, concern the formation of plasma membrane-associated lipid rafts. These platforms are dynamic scaffolds which organize membrane-associated events. Elucidate the mechanisms behind this process should clarify our understanding of these pathologies.
Among a large number of lipid-actin-binding proteins able to form lipid domains, annexins have emerged as important links between intracellular Ca2+ signals and the regulation of the organisation of membrane domains. Among them, Annexin A2 (AnxA2) is involved in several cellular processes including exocytosis and membrane-cytoskeleton interactions. More recently AnxA2 has been implicated in the regulation of nociception via its interaction with TRPA1 and TRPV4 channels in dorsal root ganglia neurons (DRG). The common point in these different cellular processes is the binding of AnxA2 to the plasma membrane and its ability to organize membrane lipids. Recently, we have demonstrated that AnxA2 bundles actin filament to form lipid platforms required for granule docking and fusion in chromaffin cells. Thus AnxA2 displays all the biophysical properties required to organize lipid microdomains in the plasma membrane.
The objective of the thesis is to determine how AnxA2 associated with actin modifies membrane organization using two models: the formation of exocytotic sites in chromaffin cells and the targeting of TRP channels to the plasma membrane in nociceptive primary afferents neurons.

1.Role and regulation of AnxA2 and actin in lipid domains formation at exocytotic sites

In bovine chromaffin cells, the secretagogue-evoked stimulation triggers the translocation of AnxA2 to plasma membrane and the formation of cholesterol, PIP2 and GM1-enriched microdomains at exocytotic sites. Our recent results reveal that AnxA2 and the actin cytoskeleton are essential partners providing lipid platforms necessary for granule docking and fusion. This suggests that AnxA2 and actin could act by triggering the coalescence of lipid rafts required for the recruitment and/or activation of the exocytotic machinery at the right time and place. To validate this notion we will assess 1) the composition of lipid domains formed by AnxA2, 2) the kinetics of their formation in living cells, and 3) test whether, after a rise in cytosolic calcium, AnxA2 is able to create ordered lipid microdomains by clustering specific lipid molecules in the plasma membrane.

2.AnxA2 and lipid platforms in nociception:

Nociception is a sensory function that involves the detection and the processing of harmful signals by specialized primary afferent nerve fibers (nociceptors). The transient receptor potential (TRP) ion channels are expressed in the nociceptors and are ligand-gated ion channels that function as molecular detectors of physical stimuli. Neuronal TRP-channels can be activated, sensitized or inhibited by different lipids, especially PIP2. Given the roles of AnxA2 and actin in the formation of lipid platforms at the exocytosic sites, it is tempting to speculate that AnxA2 could regulate TRP channels by modifying their lipid environment through the formation of PIP2 clusters. This hypothesis will be tested by investigating 1) the presence of TRP channels in lipid microdomains, 2) the involvement of AnxA2 and actin in the formation of these lipid domains. Finally, as AnxA2 levels change during neuropathic pain conditions, we will test whether 4) the localization of AnxA2 is modified and lipid domain formation is involved in neuropathic pain. These experiments should highlight the pivotal role of lipid domain formation in sensory biology and improve our understanding of peripheral pain mechanisms.

Wished skills: Knowledge in neuroendocrinology, and cellular and molecular biology

Expertises which will be acquired during the training: Cell culture, cloning and mutagenesis, biochemistry (sub cellular
fractionation, electrophoresis and Western blot)
Confocal microscopy, TIRF, time-lapse and electronic microscopy
Amperométry