Signal transduction mechanism of cardiac stretch-activated channels

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The cardiac myocytes are always under the influence of physical force, and ion channels regulated by stretch may play important physiological roles in the heart. This research project, therefore, was designed to clarify the signal transduction mechanism around the stretch-activated ion channels in the molecular level. Candidate molecules interacting with several stretch-activated chloride channels were screened from cardiac cDNA library using the yeast two-hybrid method. The carboxyl terminus of ClC-2 channel was found to interact with three molecules that are regulated during the course of cell cycle. In vitro kinase assay revealed that the carboxyl terminus of ClC-2 was phosphorylated by p34ィイD1cdc2ィエD1/cycin B and MAP kinase. ClC-2 currents expressed in Xenopus oocytes were inhibited by p34ィイD1cdc2ィエD1/cyclin B, and were augmented by olomoucine, a cyclin-dependent kinase inhibitor. The reverse transcription PCR technique showed that the mRNA level of ClC-2 was also regulated by cell cycle, and was up-regulated in the fetal and hypertrophied heart. These data showed that ClC-2 channel was regulated by cell cycle machinery in the level of transcription, protein phosphorylation, and channel function. These mechanism may be important to achieve drastic change of cell volume during the course of cell cycle.