The P2X7 channel is involved in the pathogenesis of various CNS diseases. An increasing number of studies suggest its presence in neurons where its putative functions remain controversial for more than a decade. To resolve this issue and to provide a model for analysis of P2X7 functions, we generated P2X7 BAC transgenic mice that allow visualization of functional EGFP-tagged P2X7 receptors in vivo. Extensive characterization of these mice revealed dominant P2X7-EGFP protein expression in microglia, Bergmann glia, and oligodendrocytes, but not in neurons. These findings were further validated by microglia- and oligodendrocyte-specific P2X7 deletion and a novel P2X7-specific nanobody. In addition to the first quantitative analysis of P2X7 protein expression in the CNS, we show potential consequences of its overexpression in ischemic retina and post-traumatic cerebral cortex grey matter. This novel mouse model overcomes previous limitations in P2X7 research and will help to determine its physiological roles and contribution to diseases.

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Extracellular adenine nucleotides play important roles in cell–cell communication and tissue homeostasis. High concentrations of extracellular ATP released by dying cells are sensed as a danger signal by the P2X7 receptor, a non-specific cation channel. Studies in P2X7 knockout mice and numerous disease models have demonstrated an important role of this receptor in inflammatory processes. P2X7 activation has been shown to induce a variety of cellular responses that are not usually associated with ion channel function, for example changes in the plasma membrane composition and morphology, ectodomain shedding, activation of lipases, kinases, and transcription factors, as well as cytokine release and apoptosis. In contrast to all other P2X family members, the P2X7 receptor contains a long intracellular C-terminus that constitutes 40% of the whole protein and is considered essential for most of these effects. So far, over 50 different proteins have been identified to physically interact with the P2X7 receptor. However, few of these interactions have been confirmed in independent studies and for the majority of these proteins, the interaction domains and the physiological consequences of the interactions are only poorly described. Also, while the structure of the P2X7 extracellular domain has recently been resolved, information about the organization and structure of its C-terminal tail remains elusive. After shortly describing the structure and assembly of the P2X7 receptor, this review gives an update of the identified or proposed interaction domains within the P2X7 C-terminus, describes signaling pathways in which this receptor has been involved, and provides an overlook of the identified interaction partners.

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Background and Purpose: The synthetic compound efsevin was recently identified to suppress arrhythmogenesis in models of cardiac arrhythmia, making it a promising candidate for antiarrhythmic therapy. Its activity was shown to be dependent on the voltage-dependent anion channel 2 (VDAC2) in the outer mitochondrial membrane.Here, we investigated the molecular mechanism of the efsevin-VDAC2 interaction.Experimental Approach: To evaluate the functional interaction of efsevin and VDAC2, we measured currents through recombinant VDAC2 in planar lipid bilayers.Using molecular ligand-protein docking and mutational analysis, we identified the efsevin binding site on VDAC2. Finally, physiological consequences of the efsevininduced modulation of VDAC2 were analysed in HL-1 cardiomyocytes.Key Results: In lipid bilayers, efsevin reduced VDAC2 conductance and shifted the channel's open probability towards less anion-selective closed states. Efsevin binds to a binding pocket formed by the inner channel wall and the pore-lining N-terminal α-helix. Exchange of amino acids N207, K236 and N238 within this pocket for alanines abolished the channel's efsevin-responsiveness. Upon heterologous expression in HL-1 cardiomyocytes, both channels, wild-type VDAC2 and the efsevin-insensitive VDAC2 AAA restored mitochondrial Ca 2+ uptake, but only wild-type VDAC2 was sensitive to efsevin. Conclusion and Implications:In summary, our data indicate a direct interaction of efsevin with VDAC2 inside the channel pore that leads to modified gating and results in enhanced SR-mitochondria Ca 2+ transfer. This study sheds new light on the function of VDAC2 and provides a basis for structure-aided chemical optimization of efsevin.Abbreviations: CPVT, catecholaminergic polymorphic ventricular tachycardia; DPhPC, 1,2-diphytanoyl-sn-glycero-3-phosphatidylcholine; hVDAC2, human voltage-dependent anion channel 2; IRES, internal ribosome entry site; MCU, mitochondrial calcium uniporter; MOI, multiplicity of infection; mVDAC2, mouse voltage-dependent anion channel 2; OMM, outer mitochondrial membrane; P O , open probability; RuR, ruthenium red; shRNA, short hairpin RNA; SR, sarcoplasmic reticulum; VDAC, voltage-dependent anion channel; zVDAC2, zebrafish voltage-dependent anion channel 2.

At the CERN SPS we have measured a deep inelastic μ± cross section asymmetry at momentum transfers Q2 ranging from 15 to 180GeV2. The result is in quantitative agreement with the WS/GIM standard electroweak model and allows to determine the muon neutral current couplings