Anales RANF

S6-01 INCREASED SURFACE P2X4 RECEPTOR EXPRESSION LEADS TO SYNAPTIC PLASTICITY AND LEARNING DEFICITS IN NON- INTERNALIZED P2X4MCHERRYIN KNOCKIN MICE E. Bertin 1* , T. Deluc 1,2* , K. S. Pilch 1* , A. Martinez 1 , J-T. Pougnet 1 , E. Doudnikoff 1 , A- E. Allain 3 , P. Bergmann 4 , M. Russeau 5 , E. Toulmé 1 , E. Bezard 1 , F. Koch-Nolte 4 , P. Séguéla 3 , S. Lévi 5 , B. Bontempi 1 , F. Georges 1 , S. S. Bertrand 2 , O. Nicole 1 and E. Boué- Grabot 1 ; *, First co-authors 1 Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, Bordeaux, France ; 2 Montreal Neurological Institute, Alan Edwards Centre for Research on Pain, McGill University, Montreal, Quebec, Canada; 3 Univ. de Bordeaux, Institut de Neurosciences Cognitives et Intégratives d’Aquitaine, UMR5287, Bordeaux, France ; 4 Institute of Immunology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, 5 INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, Paris, France. ATP signaling and surface P2X4 ATP-gated receptor channels are upregulated in various neurological disorders including chronic pain, epilepsy and neurodegenerative diseases such as Alzheimer’s disease (AD) or amyotrophic lateral sclerosis (ALS). P2X4 displays a widespread distribution in CNS neurons and glial cells as well as in multiple peripheral cell types throughout the body. A key question regarding the role of purinergic signaling in health and disease is the function of this upregulated surface P2X4 state observed in specific cell types. To elucidate the cell-specific functions of P2X4 in a pathological context, we created a conditional transgenic knock-in P2X4 mouse line (floxed P2X4mCherryIN) allowing the Cre activity-dependent genetic swapping of the internalization motif of P2X4 by the fluorescent protein mCherry to prevent constitutive endocytosis of P2X4. We describe and characterize two distinct knock-in mouse lines expressing non-internalized P2X4mCherryIN either in excitatory forebrain neurons (CamK2) or in all cells natively expressing P2X4 (CMV). The genetic substitution of wild-type P2X4 by non- internalized P2X4mCherryIN in both knock-In mouse models does not alter the sparse distribution and subcellular localization of P2X4 but leads to a cell-specific increased surface P2X4 expression mimicking the pathological upregulated P2X4 state. Floxed, CamK2- and CMV-P2X4mCherryIN mice were viable, normal in size, reproduced normally and displayed no obvious physical or behavioral abnormalities. We provide evidence using a battery of behavioral tests that the increase in P2X4 at the surface of excitatory neurons decreases anxiety and impairs memory processing. In addition, we demonstrate that increased surface P2X4 expression blocks long-term potentiation (LTP) and alters LTD at hippocampal CA1 synapses. These effects are more pronounced when surface P2X4 expression is specifically increased in forebrain excitatory neurons. The key finding of this study is that the increased surface expression of P2X4 in forebrain excitatory neurons is a major regulator of hippocampal synaptic plasticity, learning and memory and anxiety functions. Overall, we provide an innovative knock-in P2X4 model to study the functional contributions of upregulated P2X4 in specific cells of the nervous system but also in peripheral tissues throughout the body. This work was supported by CNRS, University of Bordeaux, the grant LabEx BRAIN ANR-10-LABX-43, a grant Inserm for the generation of the mouse line.