Acid-Sensing Ion Channel 3 (ASIC3) is a member of the Degenerin/Epithelial Na+ Channel (ENaC) superfamily and primarily conducts Na+. It is mainly expressed in the peripheral nervous system and has an important role in pain sensation. ASIC3 conducts rapidly desensitizing currents when activated by protons. RFamides can slow desensitization of ASIC3, but their binding site is yet unknown. In this study we used the most potent RFamide, RPRFamide, to explore the RFamide interaction with ASIC3. We first showed that the RPRFamide derivative RPR[azido]Famide can be covalently linked to ASIC3 by UV irradiation. When RPR[azido]Famide was covalently linked to ASIC3, desensitization was prevented. We conclude that RPRFamide stabilizes the open state of ASIC3 and has to unbind before desensitization. Next, we applied in silico docking and identified two potential binding sites: The nonproton ligand sensing domain, which is located in a central extracellular cavity, and the acidic pocket, an extracellular pocket located on the surface of the extracellular domain. Based on the docking results we created and analysed 40 ASIC3 mutants. These mutants indicate that the nonproton ligand sensing domain has an import role in RPRFamide modulation of ASIC3. In conclusion we show that RPRFamide probably stabilizes the open state of ASIC3 by binding to the nonproton ligand sensing domain.
Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA284
Poster Communications: RPRFamide interacts with the nonproton ligand sensing domain and slows desensitization by stabilizing the open conformation of Acid-Sensing Ion Channel 3
M. Reiners1, M. Margreiter3, A. Oslender-Bujotzek1, G. Rossetti2,3, S. Gründer1, A. Schmidt1
1. Institute of Physiology, RWTH Aachen University, Aachen, Germany. 2. Department of Oncology, Hematology and Stem Cell Transplantation, RWTH Aachen University, Aachen, Germany. 3. Computational Biomedicine - Institute for Advanced Simulation (IAS)/Institute of Neuroscience and Medicine (INM) and Jülich Supercomputing Centre (JSC), Forschungszentrum Jülich, Jülich, Germany.
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Where applicable, experiments conform with Society ethical requirements.