The role of the potassium channel TRESK for the development and function of T lymphocytes in autoimmune neuroinflammation

• Applicant: Professor Dr. Stefan Bittner
• Subject Area: Molecular and Cellular Neurology and Neuropathology ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 269939884

Two-pore domain potassium (K2P) channels are key components in shaping cellular functions under multiple physiological and pathophysiological circumstances. They are a major determinant of the background potassium conductance and counteract membrane potential depolarization. Recently, we could establish a key role of the K2P channel family members TASK1-3 (KCNK3,5,9) for the activation and effector functions of T lymphocytes in vitro and in animal models of multiple sclerosis (experimental autoimmune encephalomyelitis, EAE).TRESK (KCNK18) is the last discovered member of the K2P channel family. Electrophysiological, structural and functional data indicate that KCNK18 exhibits individual characteristics within this family as it is for example activated by an increase of intracellular calcium levels. It possesses a unique structure with a long intracellular loop containing an evolutionary conserved high-affinity binding site for calcineurin. Interestingly, calcineurin activity is tightly regulated within T lymphocytes as activation threshold by calcium levels is in the physiological range of T lymphocytes and as it has only a low affinity to NFAT proteins. The principal aim of this study is to investigate the role of TRESK for T cell physiology. We hypothesize that TRESK channels show a dual-mode of action based on both an ion pore function and a calcineurin-binding domain. Three newly generated genetically modified mice will be used to dissect the physiological functions of TRESK on T lymphocytes. Therefore, we will compare Tresk-/- (full knockout), TreskG339R (pore domain mutation inhibiting ion flow) and TreskS276A (constitutively active TRESK channels) mice. At first, we will investigate the functional contribution of TRESK channels to the activation, differentiation and effector functions of T lymphocytes with a special focus on calcineurin-dependent pathways using molecularbiological, electrophysiological and immunological methods. A special focus will be put on the role of TRESK channels for the development and functional properties of CD4+CD25+FoxP3+ regulatory T lymphocytes as preliminary data point towards an important role of TRESK within thymic development processes. Thereafter, we will challenge the in vivo relevance of the different TRESK channel functions in animal models of autoimmune neuroinflammation. In-depth analysis of the immunological phenotype will provide evidence about the involvement of TRESK under pathophysiological circumstances. Finally, we will investigate the the human relevance of TRESK using samples from the peripheral blood, thymus sections and brain specimen from patients with multiple sclerosis.

• DFG Programme: Research Grants