TY - JOUR
T1 - Up-regulation of the IKCa1 potassium channel during T-cell activation
T2 - Molecular mechanism and functional consequences
AU - Ghanshani, Sanjiv
AU - Wulff, Heike
AU - Miller, Mark J.
AU - Rohm, Heike
AU - Neben, Amber
AU - Gutman, George A.
AU - Cahalan, Michael D.
AU - Chandy, K. George
PY - 2000/11/24
Y1 - 2000/11/24
N2 - We used whole cell recording to evaluate functional expression of the intermediate conductance Ca2+-actirated K+ channel, IKCa1, in response to various mitogenic stimuli. One to two days following engagement of T-cell receptors to trigger both PKC- and Ca2+-dependent events, IgCa1 expression increased from an average of 8 to 300-800 channels/cell. Selective stimulation of the PKC pathway resulted in equivalent up-regulation, whereas a calcium ionophore was relatively ineffective. Enhancement in IKCa1 mRNA levels paralleled the increased channel number. The genomic organization of IKCa1, SKCa2, and SKCa3 were defined, and IK(Ca) and SK(Ca) genes were found to have a remarkably similar intron-exon structure. Mitogens enhanced IKCa1 promoter activity proportional to the increase in IKCa1 mRNA, suggesting that transcriptional mechanisms underlie channel up-regulation. Mutation of motifs for AP1 and Ikaros-2 in the promoter abolished this induction. Selective Kv1.3 inhibitors ShK-Dap22, margatoxin, and correolide suppressed mitogenesis of resting T-cells but not preactivated T-cells with up-regulated IKCa1 channel expression. Selectively blocking IKCa1 channels with clotrimazole or TRAM-34 suppressed mitogenesis of preactivated lymphocytes, whereas resting T-cells were less sensitive. Thus, Kv1.3 channels are essential for activation of quiescent cells, but signaling through the PKC pathway enhances expression of IKCa1 channels that are required for continued proliferation.
AB - We used whole cell recording to evaluate functional expression of the intermediate conductance Ca2+-actirated K+ channel, IKCa1, in response to various mitogenic stimuli. One to two days following engagement of T-cell receptors to trigger both PKC- and Ca2+-dependent events, IgCa1 expression increased from an average of 8 to 300-800 channels/cell. Selective stimulation of the PKC pathway resulted in equivalent up-regulation, whereas a calcium ionophore was relatively ineffective. Enhancement in IKCa1 mRNA levels paralleled the increased channel number. The genomic organization of IKCa1, SKCa2, and SKCa3 were defined, and IK(Ca) and SK(Ca) genes were found to have a remarkably similar intron-exon structure. Mitogens enhanced IKCa1 promoter activity proportional to the increase in IKCa1 mRNA, suggesting that transcriptional mechanisms underlie channel up-regulation. Mutation of motifs for AP1 and Ikaros-2 in the promoter abolished this induction. Selective Kv1.3 inhibitors ShK-Dap22, margatoxin, and correolide suppressed mitogenesis of resting T-cells but not preactivated T-cells with up-regulated IKCa1 channel expression. Selectively blocking IKCa1 channels with clotrimazole or TRAM-34 suppressed mitogenesis of preactivated lymphocytes, whereas resting T-cells were less sensitive. Thus, Kv1.3 channels are essential for activation of quiescent cells, but signaling through the PKC pathway enhances expression of IKCa1 channels that are required for continued proliferation.
UR - http://www.scopus.com/inward/record.url?scp=0034711234&partnerID=8YFLogxK
U2 - 10.1074/jbc.M003941200
DO - 10.1074/jbc.M003941200
M3 - Article
C2 - 10961988
AN - SCOPUS:0034711234
VL - 275
SP - 37137
EP - 37149
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 47
ER -