Abstract
Mechano-sensitive channels (MSCs) have been implicated to mediate the mechano-sensation of various types of cells. It has been well established that, in prokaryotes, MSCs can be activated directly by tension in the membrane. In contrast, the mechanism for eukaryotic MSCs activation has remained unclear. Since isolated eukaryotic MSCs in liposome could not be activated, it is proposed that eukaryotic MSCs may form molecular complex with other accessory proteins such as cytoskeletons for their function. To address this issue, we have investigated lateral mobility of hSAKcaCs (human stretch activated and Ca2+-activated big K channels), which we have recently identified, in the plasma membrane of living cells. We have expressed GFP-tagged hSAKcaCs in HeLa cells and observed individual channels by single fluorophore video imaging using total internal reflection fluorescence microscopy. Most of hSAKcaCs exhibited simple diffusion (diffusion coefficient, 0.4 μm2/s on average), but approximately 25% of the channels was almost stationary. The observation of single channels of hSAKcaC simultaneously with RFP-tagged paxillin showed that these immobilized channels were specifically localized on/near focal contacts. These results suggest that hSAKcaCs may associate with the force-transmitting modules including adhesion molecules and cytoskeletons to form a mechano-sensing device. [J Physiol Sci. 2006;56 Suppl:S82]
