page_title: Mechanosensitive channels
section_title: Gating mechanism
hierarchical_section_title: Mechanosensitive channels / Gating mechanism
caption_attribution_description: English: Stretch model
context_page_description: Mechanosensitive channels, mechanosensitive ion channels or stretch-gated ion channels. They are present in the membranes of organisms from the three domains of life: bacteria, archaea, and eukarya. 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. 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. MSCs function as mechanotransducers capable of generating both electrical and ion flux signals as a response to external or internal stimuli. 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.
context_section_description: Although MS vary in many aspects, structures and functions, all the MS studied to date share an important feature: in a process called gating, they all open in a pore-like manner when protein channels are activated by a mechanical stimulus. There are currently two models of the gating process that explain how membrane-activated ion channels open.
  Lipid bilayer Tension or stretch model: In this model tension in the lipid bilayer triggers conformational changes, thus leading to the opening of the channels. The tension perceived by the protein comes from the lipids. It has been demonstrated that the tension/stretch profile in the lipid bilayer is originated by membrane curvature and bilayer-protein hydrophobic mismatch.
  Spring-like Tether model: In this model a spring-like tether is attached directly to the MS channel and can be present in either the cytoskeleton or the extracellular matrix linking these elements together. When external stimuli deflect the tether the displacement opens the channel. This particular mechanism has been demonstrated to be the responsible for gating hair cells which are responsible for hearing in vertebrates.
caption: Gating Mechanism of MS.Stretch activated model, tension in the lipid bilayer triggers conformational changes which open the channel. Figure adapted from Lumpkin et al.[68]
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