14-3-3 Proteins regulate K sub(2P)5.1 surface expression on T lymphocytes

K sub(2P)5.1 channels (also called TASK-2 or Kcnk5) have already been shown to be relevant in the pathophysiology of autoimmune disease because they are known to be upregulated on peripheral and central T lymphocytes of multiple sclerosis (MS) patients. Moreover, overexpression of K sub(2P)5.1 channels in vitro provokes enhanced T-cell effector functions. However, the molecular mechanisms regulating intracellular K sub(2P)5.1 channel trafficking are unknown so far. Thus, the aim of the study is to elucidate the trafficking of K sub(2P)5.1 channels on T lymphocytes. Using mass spectrometry analysis, we have identified 14-3-3 proteins as novel binding partners of K sub(2P)5.1 channels. We show that a non-classical 14-3-3 consensus motif (R-X-X-pT/S-x) at the channel's C-terminus allows the binding between K sub(2P)5.1 and 14-3-3. The mutant K sub(2P)5.1/S266A diminishes the protein-protein interaction and reduces the amplitude of membrane currents. Application of a non-peptidic 14-3-3 inhibitor (BV02) significantly reduces the number of wild-type channels in the plasma membrane, whereas the drug has no effect on the trafficking of the mutated channel. Furthermore, blocker application reduces T-cell effector functions. Taken together, we demonstrate that 14-3-3 interacts with K sub(2P)5.1 and plays an important role in channel trafficking. K sub(2P)5.1 channels possess a putative non-classical consensus motif for 14-3-3 proteins that mediates the interaction and promotes K sub(2P)5.1 channels to the plasma membrane. An amino acid mutation reduces the binding of 14-3-3 proteins to K sub(2P)5.1 resulting in a reduced number of channels at the plasma membrane and a decreased potassium efflux. Pharmacological inhibition of 14-3-3 protein binding to K sub(2P)5.1 functionally impacts T-cell proliferation and cytokine production. 14-3-3 proteins may represent a pharmacological target for the treatment of multiple sclerosis and other autoimmune diseases.