Cloning of a stretch-inhibitable nonselective cation channel

A homologue of the capsaicin receptor-nonselective cation channel was clone d from the rat kidney to investigate a mechanosensitive channel. We found t his channel to be inactivated by membrane stretch and have designated it st retch-inactivated channel (SIC), SIC encodes a 563-amino acid protein with putative six transmembrane segments. The cDNA was expressed in mammalian ce lls, and electophysiological studies were performed. SIG-induced large cati on currents were found to be regulated by cell volume, with currents being stimulated by cell shrinkage and inhibited by cell swelling. Single channel analysis showed a conductance of 250 pS with cation permeability (PC1/PNa < 0.1), and the channel possessed some of the characteristics of a stretch- inactivated channel in that it was permeable to calcium, sensitive to membr ane stretch, and blocked by Gd3+. Therefore, we cloned one of the mechanose nsitive cation channels of mammals, which is considered to regulate Ca2+ in flux in response to mechanical stress on the cell membrane.