Differential Functional Expression of Clotrimazole-sensitive Ca<SUP>2&#8290;</SUP>-activated K<SUP>&#8290;</SUP> Current in Bal-17 and WEHI-231 Murine B Lymphocytes

Differential Functional Expression of Clotrimazole-sensitive Ca<SUP>2&#8290;</SUP>-activated K<SUP>&#8290;</SUP> Current in Bal-17 and WEHI-231 Murine B Lymphocytes

The intermediate conductance Ca<SUP>2&#8290;</SUP>-activated K<SUP>&#8290;</SUP> channels (SK4, IKCa1) are present in lymphocytes, and their membrane expression is upregulated by various immunological stimuli. In this study, the activity of SK4 was compared between Bal-17 and WEHI-231 cell lines which represent mature and immature stages of murine B lymphocytes, respectively. The whole-cell patch clamp with high-Ca<SUP>2&#8290;</SUP> (0.8μM) KCl pipette solution revealed a voltage-independent K<SUP>&#8290;</SUP> current that was blocked by clotrimazole (1 mM), an SK4 blocker. The expression of mRNAs for SK4 was confirmed in both Bal-17 and WEHI-231 cells. The density of clotrimazole-sensitive SK4 current was significantly larger in Bal-17 than WEHI-231 cells (&#8291;11.4&#8273;3.1 Vs. &#8291;5.7&#8273;1.15 pA/pF). Also, the chronic stimulation of B cell receptors (BCR) by BCR-ligation (anti-IgM Ab, 3μg/ml, 8∼12 h) significantly upregulated the amplitude of clotrimazole- sensitive current from &#8291;11.4&#8273;3.1 to &#8291;53.1&#8273;8.6 pA/pF in Bal-17 cells. In WEHI-231 cells, the effect of BCR-ligation was significantly small (&#8291;5.7&#8273;1.15 to &#8291;9.0&#8273;1.00 pA/pF). The differential expression and regulation by BCR-ligation might reflect functional changes in the maturation of B lymphocytes.