Mechanosensitive channels

Mechanosensitive channels (MSCs), mechanosensitive ion channels or stretch-gated ion channels are membrane proteins capable of responding to mechanical stress over a wide dynamic range of external mechanical stimuli.^[1][2][3][4] They are present in the membranes of organisms from the three domains of life: bacteria, archaea, and eukarya.^[5] They are the sensors for a number of systems including the senses of touch, hearing and balance, as well as participating in cardiovascular regulation and osmotic homeostasis (e.g. thirst). The channels vary in selectivity for the permeating ions from nonselective between anions and cations in bacteria, to cation selective allowing passage Ca²⁺, K⁺ and Na⁺ in eukaryotes, and highly selective K⁺ channels in bacteria and eukaryotes.

All organisms, and apparently all cell types, sense and respond to mechanical stimuli.^[6] MSCs function as mechanotransducers capable of generating both electrical and ion flux signals as a response to external or internal^[7] stimuli.^[8] Under extreme turgor in bacteria, non selective MSCs such as MSCL and MSCS serve as safety valves to prevent lysis. In specialized cells of the higher organisms, other types of MSCs are probably the basis of the senses of hearing and touch and sense the stress needed for muscular coordination. However, none of these channels have been cloned. MSCs also allow plants to distinguish up from down by sensing the force of gravity. MSCs are not pressure-sensitive, but sensitive to local stress, most likely tension in the surrounding lipid bilayer.^[9]