Inhibition of voltage-gated K+ channels in dendritic cells by rapamycin

Rapamycin, an inhibitor of the serine/threonine kinase mammalian target of rapamycin (mTOR), is a widely used immunosuppressive drug. Rapamycin affects the function of dendritic cells (DCs), antigen-presenting cells participating in the initiation of primary immune responses and the establishment of immunological memory. Voltage-gated K(+) (Kv) channels are expressed in and impact on the function of DCs. The present study explored whether rapamycin influences Kv channels in DCs. To this end, DCs were isolated from murine bone marrow and ion channel activity was determined by whole cell patch clamp. To more directly analyze an effect of mTOR on Kv channel activity, Kv1.3 and Kv1.5 were expressed in Xenopus oocytes with or without the additional expression of mTOR and voltage-gated currents were determined by dual-electrode voltage clamp. As a result, preincubation with rapamycin (0-50 nM) led to a gradual decline of Kv currents in DCs, reaching statistical significance within 6 h and 50 nM of rapamycin. Rapamycin accelerated Kv channel inactivation. Coexpression of mTOR upregulated Kv1.3 and Kv1.5 currents in Xenopus oocytes. Furthermore, mTOR accelerated Kv1.3 channel activation and slowed down Kv1.3 channel inactivation. In conclusion, mTOR stimulates Kv channels, an effect contributing to the immunomodulating properties of rapamycin in DCs.