Abstract
Mechanosensitive channels (MSCs) have been implicated to play key roles in mechanotransduction of a variety of cells. Yet little is known on their physiological functions. One of major reasons is a lack of inhibitors specific to MSCs. Gadolinium and aminoglycosides have been used as potential MSC inhibitors, however, they have relatively high Kds over 10 uM and inhibit several ion channels other than MSCs. Very recently the peptide GsMTx-4 from a spider (Grammostola spatulata) venom was reported to be a promising candidate for a specific inhibitor of MSCs. We tested if GsMTx-4 inhibits Stretch-Activated and Ca-activated K channel (SAKcaC) and its loss-of-mechanosensitivity mutant by use of the back-fill method with excised inside-out patches. Open probability (Po) of SAKcaC was significantly reduced by nM range of GsMTx-4. Analysis of the effect of GsMTx-4 on the Po-V curve of SAKcaC revealed that the peptide acts as a gating modifier rather than a channel blocker. In contrast GsMTx-4 scarcely inhibited the loss-of-mechanosensitivity mutant, suggesting that GsTMx-4 would work as an inihibitor selective to MSCs. Inspired by these results, we designed and synthetized a variety of peptide mimetics of GsMTx-4. Among them a decamer peptide, which shares the sequence with the flexible loop2 in GsMTx-4, was found to inhibit SAKcaC in the same manner as GsMTx-4 with a lower Kd. This result opens up a promising way to synthetize a new class of MSC-specific inhibitors. [Jpn J Physiol 55 Suppl:S136 (2005)]
