Regulation of Kv1.3 channels in activated human T lymphocytes by Ca2+-dependent pathways

Activated T lymphoblasts respond more effectively to mitogenic stimuli than resting T cells, partly through differences in Ca2+ signaling, which in tu rn depend on K+ channel activity. Both Kv1.3 and Ca2+-activated K+ (SK4) ch annels are up-regulated in T lymphoblasts. Since Ca2+- and calmodulin (CaM) -dependent signaling are key pathways in T-cell activation, we investigated their involvement in regulating the Kv1.3 current. Kv1.3 in lymphoblasts w as significantly inhibited by elevating internal Ca2+ to the micromlolar le vel. it was also reduced in a Ca2+-dependent manner by inhibiting CaM with W-7 or calmidazolium. F)art of the CaM-dependence is likely through CaM kin ase since the current was also inhibited by the antagonist, KN-62, but not by the inactive analogue, KN-04. Kinase inhibition, unlike CaM inhibition, was only effective at physiological temperatures, a difference that implies involvement of more than one mechanism. We demonstrated a biochemical asso ciation of Kv1.3 protein in lymphoblasts with the multifunctional type II C aM kinase, but not with calmodulin. Thus, Kv1.3 forms a multi-protein compl ex with CaM kinase II (which binds to Ca2+/CaM) and previously identified p roteins (e.g,, PSD-95, sre tyrosine kinase) that position the channel to re spond to signaling pathways that are crucial for T-cell activation and prol iferation. Copyright (C) 2001 S. Karger AG, Basel.