Ca2+-activated K+ channels in human leukemic Jurkat T cells. Molecular cloning, biochemical and functional characterization.
Previous studies have demonstrated the presence of apamin-sensitive, small-conductance Ca(2+)-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 Ca(2+)-activated K(+) currents with a unitary conductance of 9.5 pS and a K(0.5) for calcium of 0.7 microm; hSK2 currents are inhibited by apamin, scyllatoxin, and d-tubocurarine. Overexpression of the Src family tyrosine kinase p56(lck) in Jurkat cells, up-regulates 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.
Desai
R
R
Department of Neurobiology, The Weizmann Institute of Science, 76100 Rehovot, Israel.
Peretz
A
A
Idelson
H
H
Lazarovici
P
P
Attali
B
B
D000595:Amino Acid Sequence; D001030:Apamin / Q000494:pharmacology; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D003001:Cloning, Molecular; D017931:DNA Primers; D006801:Humans; D019169:Jurkat Cells; D008969:Molecular Sequence Data; D010802:Phylogeny; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D015221:Potassium Channels; D001030:Apamin; D002118:Calcium