Previous studies have demonstrated the presence of apamin-sensitive, small-conductance Ca2+-activated K+ currents in human leukemic Jurkat T cells. Using a combined cDNA and reverse transcriptase-polymerase chain reaction cloning strategy, we have isolated from Jurkat T cells a 2.5-kilobase cDNA, hSK2, encoding the human isoform of SK2 channels. Northern blot analysis reveals the presence of a 2.5-kilobase hSK2 transcript in Jurkat T cells. While present in various human tissues, including brain, heart, skeletal muscle, kidney, and liver, no hSK2 mRNA could be detected in resting and activated normal human T cells. The hSK2 gene is encoded by 8 exons and could be assigned to chromosome 5 (q21.2-q22.1). The protein encoded by hSK2 is 579 amino acids long and exhibits 97% identity with its rat counterpart rSK2. When expressed in Chinese hamster ovary cells, hSK2 produces Ca2+-activated K+ currents with a unitary conductance of 9.5 pS and a K0.5 for calcium of 0.7 μM; hSK2 currents are inhibited by apamin, scyllatoxin, and d-tubocurarine. Overexpression of the Src family tyrosine kinase p56lck in Jurkat cells, upregulates SK2 currents by 3-fold. While IKCa channels are transcriptionally induced upon activation of normal human T cells, our results show that in Jurkat cells SK2 channels are constitutively expressed and down-regulated following mitogenic stimulation.
CITATION STYLE
Desai, R., Peretz, A., Idelson, H., Lazarovici, P., & Attali, B. (2000). Ca2+-activated K+ channels in human leukemic Jurkat T cells. Journal of Biological Chemistry, 275(51), 39954–39963. https://doi.org/10.1074/jbc.M001562200
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