Sensing Mechanism of Stretch Activated Ion Channels

Abstract

Most of eukaryotic and prokaryotic cells possess mechanosensitive ion (MS) channels that sense mechanical force associated with cellular functions such as proliferation, differentiation, development and cell death via changes of MS channel activity. Accurate sensing mechanical force such as osmotic pressure, hydrostatic pressure, shear stress, and gravity is essential for critical strategy to survive and adapt to a new environment. Recent electrophysilogical, biochemical, and crystallographic evidences have revealed detailed 3D structures and characteristics of MS channel proteins in prokaryotic (bacteria) cells, which lead to understanding molecular mechanisms of MS channel gating in response to mechanical force. Especially, gating of MscS (mechanosensitive ion channel with small conductance) and MscL (mechanosensitive ion channel with large conductance) in bacteria cells is well studied. Purified MS channel proteins of bacteria directly sense membrane tension as mechanical force from lipid bilayer without other components that provide the driving energy for the MS channel to change the open conformation. In contrast, MS channels in eukaryotic cells (higher organisms) sense the magnitude and the direction of mechanical force through cytoskeltons near the lipid bilayer that are assumed to transmit the mechanical force. In this review, we summarize various sensing mechanisms of MS channels for mechanical force and discuss the physiological importance of MS channels to regulate cellular functions in their expressed cells and tissues.