Overview
Physical activity and an adequate daily mechanical loading are essential for good physical health. However, the cellular and molecular mechanisms in force sensing are not well understood today. As the gating properties of mechanosensitive ion channels (MSC) depend on mechanical force, MSCs have been proposed as cellular force sensors. Interestingly, previous studies suggest that some ion channels could also be gravity dependent, despite the fact that gravity is a very small physical force at the cellular level. Therefore, MSC could play key roles in multiple symptoms seen in individuals with insufficient daily physical stimulation, such as astronauts in orbit, bed ridden patients and the elderly. However, to date it has not been possible to demonstrate a gravity dependency of specific target ion channels.
In order to elucidate the base of this phenomena and to shed new light onto the mechanosensitivity of ion channels, we examined whether the MSC PIEZO1 shows gravity dependency. The non-selective cation channel PIEZO1 is a well described MSC and represents an interesting first candidate. For this study, a tailored version of a so called two-electrode voltage clamp (TEVC) was developed, which allowed us to conduct electrophysiological experiments on frog eggs (Xenopus laevis oocytes) overexpressing PIEZO1, during microgravity. The TEVC is a well-known setup for whole cell recordings, which does not locally stress the membrane, as it is the case in conventional patch-clamping methods.
