Regulation of Kv1.3 channels in activated human T lymphocytes by Ca(2+)-dependent pathways.
Activated T lymphoblasts respond more effectively to mitogenic stimuli than resting T cells, partly through differences in Ca(2+) signaling, which in turn depend on K(+) channel activity. Both Kv1.3 and Ca(2+)-activated K(+) (SK4) channels are up-regulated in T lymphoblasts. Since Ca(2+)- and calmodulin (CaM)-dependent signal-ing are key pathways in T-cell activation, we investigated their involvement in regulating the Kv1.3 current. Kv1.3 in lymphoblasts was significantly inhibited by elevating internal Ca(2+) to the micromolar level. It was also reduced in a Ca(2+)-dependent manner by inhibiting CaM with W-7 or calmidazolium. Part of the CaM-dependence is likely through CaM kinase 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 association of Kv1.3 protein in lymphoblasts with the multifunctional type II CaM kinase, but not with calmodulin. Thus, Kv1.3 forms a multi-protein complex with CaM kinase II (which binds to Ca(2+)/CaM) and previously identified proteins (e.g., PSD-95, src tyrosine kinase) that position the channel to respond to signaling pathways that are crucial for T-cell activation and proliferation.
Chang
M C
MC
Division of Cellular and Molecular Biology, Toronto Western Research Institute, University Health Network.
Khanna
R
R
Schlichter
L C
LC
D002118:Calcium / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002147:Calmodulin / Q000037:antagonists & inhibitors; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D051664:Kv1.3 Potassium Channel; D008213:Lymphocyte Activation; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011485:Protein Binding; D013449:Sulfonamides / Q000494:pharmacology; D013601:T-Lymphocytes / Q000378:metabolism*
D002147:Calmodulin; D007093:Imidazoles; C496973:KCNA3 protein, human; D051664:Kv1.3 Potassium Channel; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D013449:Sulfonamides; C031938:calmidazolium; C017967:W 7; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium