The tension-transmitting 'clutch' in the mechanosensitive channel MscS

Belyy, Vladislav; Anishkin, Andriy; Kamaraju, Kishore; Liu, Naili; Sukharev, Sergei

doi:10.1038/nsmb.1775

Cited by 76 publications

(94 citation statements)

References 35 publications

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“…The relaxation of the outer leaflet of the membrane in an excised patch described in ref. 53 has little effect on the tension at which MSL10 closes, because it stayed very close to zero in the majority of our experiments regardless of the ramp speed.…”

Section: Discussionmentioning

confidence: 93%

MscS-Like10 is a stretch-activated ion channel from Arabidopsis thaliana with a preference for anions

Maksaev

Haswell

2012

Proc. Natl. Acad. Sci. U.S.A.

128

156

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Like many other organisms, plants are capable of sensing and responding to mechanical stimuli such as touch, osmotic pressure, and gravity. One mechanism for the perception of force is the activation of mechanosensitive (or stretch-activated) ion channels, and a number of mechanosensitive channel activities have been described in plant membranes. Based on their homology to the bacterial mechanosensitive channel MscS, the 10 MscS-Like (MSL) proteins of Arabidopsis thaliana have been hypothesized to form mechanosensitive channels in plant cell and organelle membranes. However, definitive proof that MSLs form mechanosensitive channels has been lacking. Here we used single-channel patch clamp electrophysiology to show that MSL10 is capable of providing a MS channel activity when heterologously expressed in Xenopus laevis oocytes. This channel had a conductance of ∼100 pS, consistent with the hypothesis that it underlies an activity previously observed in the plasma membrane of plant root cells. We found that MSL10 formed a channel with a moderate preference for anions, which was modulated by strongly positive and negative membrane potentials, and was reversibly inhibited by gadolinium, a known inhibitor of mechanosensitive channels. MSL10 demonstrated asymmetric activation/ inactivation kinetics, with the channel closing at substantially lower tensions than channel opening. The electrophysiological characterization of MSL10 reported here provides insight into the evolution of structure and function of this important family of proteins.T he perception of mechanical stimuli like gravity, touch, or osmotic pressure is essential to normal plant growth and development and is further implicated in biotic and abiotic stress responses (1). One of the best-studied strategies for perceiving force involves membrane-embedded channels that are gated by tension, known as mechanosensitive (MS) channels (2). Numerous MS channel activities (>17 to date) have been described in the membranes of diverse tissues from a variety of plant species (summarized in ref. 3, also refs. 4 and 5). Many of these observed MS channel activities differ in their conductance, ion selectivity, and/or sensitivity to the direction of activation pressure, suggesting that multiple classes of mechanosensitive channels are present in plant cells.No mechanosensitive ion channel activity discovered in plant membranes has yet been definitively identified at the molecular level, but two families of proteins serve as strong candidates. The first is the Mid1-Complementing Activity (MCA) family, members of which are required for root response to touch in the model plant Arabidopsis thaliana, induce Ca 2+ uptake in rice and Arabidopsis cells (6, 7), and are associated with increased current in response to hypotonic stimulation of Xenopus oocytes (8). The second family of candidates for plant MS channels is the MscS-Like (MSL) family, first identified based on modest homology to the wellcharacterized bacterial MS channel MscS from Escherichia coli (3, 9). MscS is a lar...

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Section: Discussionmentioning

confidence: 93%

MscS-Like10 is a stretch-activated ion channel from Arabidopsis thaliana with a preference for anions

Maksaev

Haswell

2012

Proc. Natl. Acad. Sci. U.S.A.

128

156

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“…Channel gating thresholds have been frequently used in the studies of bacterial MS channels to estimate the mechanosensitivity of MscS and MscL (15,16). Instead of measuring the first channel opening of MscS and MscL to determine the TR, an alternative method is to calculate the midpoint ratio (MR) from an activation curve with the midpoints determined as the pressure (tension) at which instantaneous current is half of the current at saturation (17,18). It remained unclear which pair of parameters characterizes better the difference in MscL and MscS tension sensitivities.…”

Section: Resultsmentioning

confidence: 99%

Differential effects of lipids and lyso-lipids on the mechanosensitivity of the mechanosensitive channels MscL and MscS

Nomura

Cranfield

Deplazes

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

180

227

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Mechanosensitive (MS) channels of small (MscS) and large (MscL) conductance are the major players in the protection of bacterial cells against hypoosmotic shock. Although a great deal is known about structure and function of these channels, much less is known about how membrane lipids may influence their mechanosensitivity and function. In this study, we use liposome coreconstitution to examine the effects of different types of lipids on MscS and MscL mechanosensitivity simultaneously using the patch-clamp technique and confocal microscopy. Fluorescence lifetime imaging (FLIM)-FRET microscopy demonstrated that coreconstitution of MscS and MscL led to clustering of these channels causing a significant increase in the MscS activation threshold. Furthermore, the MscL/MscS threshold ratio dramatically decreased in thinner compared with thicker bilayers and upon addition of cholesterol, known to affect the bilayer thickness, stiffness and pressure profile. In contrast, application of micromolar concentrations of lysophosphatidylcholine (LPC) led to an increase of the MscL/MscS threshold ratio. These data suggest that differences in hydrophobic mismatch and bilayer stiffness, change in transbilayer pressure profile, and close proximity of MscL and MscS affect the structural dynamics of both channels to a different extent. Our findings may have far-reaching implications for other types of ion channels and membrane proteins that, like MscL and MscS, may coexist in multiple molecular complexes and, consequently, have their activation characteristics significantly affected by changes in the lipid environment and their proximity to each other.Escherichia coli | giant spheroplasts | liposomes | amphipaths | pressure clamp

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“…Viscosity can arise from the untangling of filamentous structures or the reversible breaking of non-covalent bonds (slip bonds) between structures or domains (Bustamante et al, 2004;Vogel, 2006;Moore et al, 2010). These slip bonds can also exist within the channel itself, as in the bacterial channel MscS (Akitake et al, 2005;Belyy et al, 2010a) (Fig. 3).…”

Section: The Energy Involved In Mechanical Transductionmentioning

confidence: 99%

Molecular force transduction by ion channels – diversity and unifying principles

Sukharev

Sachs

2012

Journal of Cell Science

Self Cite

147

140

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SummaryCells perceive force through a variety of molecular sensors, of which the mechanosensitive ion channels are the most efficient and act the fastest. These channels apparently evolved to prevent osmotic lysis of the cell as a result of metabolite accumulation and/or external changes in osmolarity. From this simple beginning, nature developed specific mechanosensitive enzymes that allow us to hear, maintain balance, feel touch and regulate many systemic variables, such as blood pressure. For a channel to be mechanosensitive it needs to respond to mechanical stresses by changing its shape between the closed and open states. In that way, forces within the lipid bilayer or within a protein link can do work on the channel and stabilize its state. Ion channels have the highest turnover rates of all enzymes, and they can act as both sensors and effectors, providing the necessary fluxes to relieve osmotic pressure, shift the membrane potential or initiate chemical signaling. In this Commentary, we focus on the common mechanisms by which mechanical forces and the local environment can regulate membrane protein structure, and more specifically, mechanosensitive ion channels.

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The tension-transmitting 'clutch' in the mechanosensitive channel MscS

Cited by 76 publications

References 35 publications

MscS-Like10 is a stretch-activated ion channel from Arabidopsis thaliana with a preference for anions

MscS-Like10 is a stretch-activated ion channel from Arabidopsis thaliana with a preference for anions

Differential effects of lipids and lyso-lipids on the mechanosensitivity of the mechanosensitive channels MscL and MscS

Molecular force transduction by ion channels – diversity and unifying principles

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