Analysis of a newly cloned stretch-activated ion channel from cardiac cells

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Stretch-sensing mechanisms of stretch-activated (SA) channels have been extensively studied and many molecular models have been presented. Here we cloned a stretch-activated, large-conductance (BK) channel from cultured chick embryonic heart and found out that the channel contains "STREX" sequence, originally reported to be a target sequence of PKA and whose expression is regulated by stress hormones, and that it turned out to contain a mechano-sensive domain of the channel. Deletion of STREX or substitution of Ala^<674> to Thr^<674> diminished stretch-sensitivity of the channel. When compared the chick STREX with mouse, rabbit STREX, which did not have any stretch-sensitivity in CHO cells, it turned out that the sequence ERA is most likely to be important. When chick STREX-EGFP was co-expressed with SAKCA in CHO cells, a strong signal was detected at cell membrane and stretch-sensitivity of the channel was significantly inhibited.