In the bright fields, stomata of the plants are fully opened to raise the transpiration rate and CO2 uptake required for photosynthesis. Stomatal opening is driven by the activation of plasma membrane H+-ATPase and K+in channels, and the Ca2+-dependent inactivation and blockage of both components were supposed to be inevitable function to regulate the stomatal aperture. Although, it is still obscure how these activities are regulated at the open state. Application of an amphipathic membrane creator, trinitrophenol (TNP), instantly generates the convex curvature in the plasma membrane, which occurs in the phases of stomatal opening and closure. TNP surely activates mechanosensitive Ca2+-permeable channels and attenuates the promotion of stomatal opening, but does not inhibit and promote stomatal closure. These results suggest that activation of mechanosensitive Ca2+-permeable channels regulates the opening phase of stomata in plants. 相似文献
Mechanosensitive (MS) ion channels are molecular sensors that detect and transduce signals across prokaryotic and eukaryotic cell membranes arising from external mechanical stimuli or osmotic gradients. They play an integral role in mechanosensory responses including touch, hearing, and proprioception by opening or closing in order to facilitate or prevent the flow of ions and organic osmolytes. In this study we use a linear force model of MS channel gating to determine the gating membrane tension (γ) and the gating area change (ΔA) associated with the energetics of MscS channel gating in giant spheroplasts and azolectin liposomes. Analysis of Boltzmann distribution functions describing the dependence of MscS channel gating on membrane tension indicated that the gating area change (ΔA) was the same for MscS channels recorded in both preparations. The comparison of the membrane tension (γ) gating the channel, however, showed a significant difference between the MscS channel activities in these two preparations. 相似文献
Mechanosensation in bacteria involves transducing membrane stress into an electrochemical response. In Escherichia coli and other bacteria, this function is carried out by a number of proteins including MscL, the mechanosensitive channel of large conductance. MscL is the best characterized of all mechanosensitive channels. It has been the subject of numerous structural and functional investigations. The explosion in experimental data on MscL recently culminated in the solution of the three-dimensional structure of the MscL homologue from Mycobacterium tuberculosis. In this review, much of these data are united and interpreted in terms of the newly published M. tuberculosis MscL crystal structure. 相似文献
Enterochromaffin (EC) cells are the primary mechanosensors of the gastrointestinal (GI) epithelium. In response to mechanical stimuliEC cells release serotonin (5-hydroxytryptamine; 5-HT). The molecular details ofEC cell mechanosensitivity are poorly understood. Recently, our group found that human and mouseEC cells express the mechanosensitive ion channel Piezo2. The mechanosensitive currents in a humanEC cell model QGP-1 were blocked by the mechanosensitive channel blocker D-GsMTx4.
In the present study we aimed to characterize the effects of the mechanosensitive ion channel inhibitor spider peptide D-GsMTx4 on the mechanically stimulated currents from both QGP-1 and human Piezo2 transfected HEK-293 cells. We found co-localization of 5-HT and Piezo2 in QGP-1 cells by immunohistochemistry. QGP-1 mechanosensitive currents had biophysical properties similar to dose-dependently Piezo2 and were inhibited by D-GsMTx4. In response to direct displacement of cell membranes, human Piezo2 transiently expressed in HEK-293 cells produced robust rapidly activating and inactivating inward currents. D-GsMTx4 reversibly and dose-dependently inhibited both the potency and efficacy of Piezo2 currents in response to mechanical force. Our data demonstrate an effective inhibition of Piezo2 mechanosensitive currents by the spider peptide D-GsMTx4. 相似文献
Compelling evidence shows that intracellular free magnesium [Mg^2+]i may be a critical regulator of cell activity in eukaryotes. However, membrane transport mechanisms mediating Mg^2+ influx in mammalian cells are poorly understood. Here, we show that mechanosensitive (MS) cationic channels activated by stretch are permeable for Mg^2+ ions at different extracellular concentrations including physiological ones. Single-channel currents were recorded from cell-attached and inside-out patches on K562 leukaemia cells at various concentrations of MgCl2 when Mg^2+ was the only available carrier of inward currents. At 2 mM Mg^2+, inward mechanogated currents representing Mg^2+ influx through MS channels corresponded to the unitary conductance of about 5 pS. At higher Mg^2+ levels, only slight increase of single-channel currents and conductance occurred, implying that Mg^2+ permeation through MS channels is characterized by strong saturation. At 20 and 90 mM Mg^2+, mean conductance values for inward currents carried by Mg^2+ were rather similar, being equal to 6.8 ± 0.5 and 6.4 ± 0.5 pS, respectively. The estimation of the channel-selective permeability according to constant field equation is obviously limited due to saturation effects. We conclude that the detection of single currents is the main evidence for Mg^2+ permeation through membrane channels activated by stretch. Our single-current measurements document Mg^2+ influx through MS channels in the plasma membrane of leukaemia cells. 相似文献
Mechanosensitive (MS) channels are evolutionarily conserved membrane proteins that play essential roles in multiple cellular processes, including sensing mechanical forces and regulating osmotic pressure. Bacterial MscL and MscS are two prototypes of MS channels. Numerous structural studies, in combination with biochemical and cellular data, provide valuable insights into the mechanism of energy transfer from membrane tension to gating of the channel. We discuss these data in a unified two‐state model of thermodynamics. In addition, we propose a lipid diffusion‐mediated mechanism to explain the adaptation phenomenon of MscS. 相似文献
Summary The activity of the mechanosensitive (MS) ion channels in membrane patches, excised fromE. coli spheroplasts, was analyzed using the patch-clamp technique. Outer membranes from a mutant lacking the major lipoprotein (Lpp) and its wildtype parent were examined. The MS-channel activities in the wild-type membrane rarely revealed substates at the time resolution used. These channels showed a stretch sensitivity indicated by the IISP (the suction for ane-fold increase in channel open probability) of 4.9 mm Hg suction. The MS-channel activities oflpp included a prominent substate and showed a weaker mechano-sensitivity with an 1/Sp of 10.0 mm Hg. Whereas small amphipaths (chlorpromazine, trinitrophenol) or a larger amphipath (lysolecithin) all activated the MS channel in the wild-type membrane under minimal suction, only the larger lysolecithin could activate the MS channel in thelpp membranes. After lysolecithin addition, thelpp membrane became more effective in transmitting the stretch force to the MS channel, as indicated by a steepening of the Boltzmann curve. We discuss one interpretation of these results, in which the major lipoprotein serves as a natural amphipath inserted in the inner monolayer and the loss of this natural amphipath makes the bilayer less able to transmit the gating force. 相似文献