Release of Thioredoxin via the Mechanosensitive Channel MscL during Osmotic Downshock of Escherichia coli Cells

Ajouz, Bassam; Berrier, Catherine; Garrigues, Alexia; Besnard, Madeleine; Ghazi, Alexandre

doi:10.1074/jbc.273.41.26670

Cited by 148 publications

(132 citation statements)

References 40 publications

Supporting

Mentioning

126

Contrasting

Order By: Relevance

“…We did not detect any YggB activity in any of the examined patches (two preparations, 20 patches of each). 2 At present we cannot entirely rule out a possibility that the truncated C termini make the YggB channels unable to assembly in the membrane. However, if taken together with our former observation regarding the effect of Pronase on the assembled channels, the lack of activity in the mutant suggests strongly that the C termini may indeed be involved in activation of the YggB channel.…”

Section: Discussionmentioning

confidence: 85%

“…Bacterial MS channels protect these cells against hypoosmotic shock. Two types of MS channels from the cytoplasmic membrane of Escherichia coli, MscL and MscS, play an essential role in the physiology of this bacterium, allowing the efflux of solutes from the cytoplasm when osmolarity of the external medium decreases (2)(3)(4). MscL, the large conductance MS channel, has been cloned (5), and a quaternary structure of its closed conformation has been determined (6).…”

Section: Mechanosensitive (Ms)mentioning

confidence: 99%

See 1 more Smart Citation

C Termini of the Escherichia coli Mechanosensitive Ion Channel (MscS) Move Apart upon the Channel Opening

Koprowski¹,

Kubalski

2003

Journal of Biological Chemistry

View full text Add to dashboard Cite

Heptameric YggB is a mechanosensitive ion channel (MscS) from the inner membrane of Escherichia coli. We demonstrate, using the patch clamp technique, that cross-linking of the YggB C termini led to irreversible inhibition of the channel activities. Application of Ni 2؉ to the YggB-His 6 channels with the hexahistidine tags added to the ends of their C termini also resulted in a marked but reversible decrease of activities. Western blot revealed that YggB-His 6 oligomers are more stable in the presence of Ni 2؉ , providing evidence that Ni 2؉ is coordinated between C termini from different subunits of the channel. Intersubunit coordination of Ni 2؉ affecting channel activities occurred in the channel closed conformation and not in the open state. This may suggest that the C termini move apart upon channel opening and are involved in the channel activation. We propose that the as yet undefined C-terminal region may form a cytoplasmic gate of the channel. The results are discussed and interpreted based on the recently released quaternary structure of the channel. Mechanosensitive (MS)1 ion channels open upon membrane tension, and therefore they represent the simplest mechanosensors. MS channels have been implicated in many physiological processes from growth and cell volume regulation to hearing, blood pressure regulation, and pain sensation (reviewed in Ref. 1). Bacterial MS channels protect these cells against hypoosmotic shock. Two types of MS channels from the cytoplasmic membrane of Escherichia coli, MscL and MscS, play an essential role in the physiology of this bacterium, allowing the efflux of solutes from the cytoplasm when osmolarity of the external medium decreases (2-4). MscL, the large conductance MS channel, has been cloned (5), and a quaternary structure of its closed conformation has been determined (6). Based on this structure and the analysis of the channel gating, the open conformation has been predicted (7, 8) and experimentally confirmed (9, 10). Functional homologues of this channel have been found in other bacteria (11) and Archea (12), and structurally related protein from Neurospora has been also reported (13). The functional channel is a pentamer, and each subunit consists of two ␣-helical membrane-spanning domains TM1 and TM2 with both the C and N termini located in the cytoplasm (6). TM1s line the pore, and their hydrophobic residues form the primary, transmembrane gate (6, 14). It is postulated that there are two gates involved in the opening of the channel: the transmembrane and the cytoplasmic gates (7, 8) acting in accordance (15). The transmembrane gate is proposed to act as a pressure sensor, and upon application of pressure, this gate permits initial expansion of the channel without its full opening (7,8,10). It is proposed that the other, cytoplasmic gate, which allows full activation of the channel, is composed of five ␣-helical S1 segments of the cytoplasmic N termini being connected with TM1s via flexible linkers. According to the model, the applied pressure is transmitted to...

show abstract

Section: Discussionmentioning

confidence: 85%

Section: Mechanosensitive (Ms)mentioning

confidence: 99%

C Termini of the Escherichia coli Mechanosensitive Ion Channel (MscS) Move Apart upon the Channel Opening

Koprowski¹,

Kubalski

2003

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…The residual 60% of efflux can be explained by cell lysis, as could be inferred from the decrease in CFU in the drop plate assay and the decrease in metabolic activity upon osmotic downshift. In contrast to L. lactis, an E. coli knock-out strain released the same amount of glycine betaine as the wild type E. coli upon osmotic downshift (44), suggesting that in E. coli another MS channel compensates for the absence of MscL or that in the wild type strain MscL is not activated under the conditions used.…”

Section: Discussionmentioning

confidence: 93%

Lactococcus lactis Uses MscL as Its Principal Mechanosensitive Channel

Folgering

Moe

Schuurman-Wolters

et al. 2005

Journal of Biological Chemistry

View full text Add to dashboard Cite

The functions of the mechanosensitive channels from Lactococcus lactis were determined by biochemical, physiological, and electrophysiological methods. Patchclamp studies showed that the genes yncB and mscL encode MscS and MscL-like channels, respectively, when expressed in Escherichia coli or if the gene products were purified and reconstituted in proteoliposomes. However, unless yncB was expressed in trans, wild type membranes of L. lactis displayed only MscL activity. Membranes prepared from an mscL disruption mutant did not show any mechanosensitive channel activity, irrespective of whether the cells had been grown on low or high osmolarity medium. In osmotic downshift assays, wild type cells survived and retained 20% of the glycine betaine internalized under external high salt conditions. On the other hand, the mscL disruption mutant retained 40% of internalized glycine betaine and was significantly compromised in its survival upon osmotic downshifts. The data strongly suggest that L. lactis uses MscL as the main mechanosensitive solute release system to protect the cells under conditions of osmotic downshift.Mechanosensitive channels play an important role in prokaryotic cell volume regulation (1). In small, single-cell organisms, this regulation can mean the difference between life and death under extreme osmotic downshift conditions. By diffusion over the semipermeable cell membrane and/or aquaporins embedded in the membrane, water can enter and leave the cell until equilibrium is established between internal and external osmolality. This allows microorganisms to adapt to changes in external osmolyte concentrations. When the external osmolyte concentrations increase (hyperosmotic stress), water will leak out of the cell, causing loss of turgor, and ultimately the cell may plasmolyse. Bacteria respond to this hyperosmotic stress by rapid uptake of ions (K ϩ ) and/or compatible solutes or increasing the intracellular osmolyte concentration through synthesis of compatible solutes. The increase in internal compatible solute concentration compensates for the high external osmolality, allowing water to diffuse back and the cell to regain its original volume and turgor (2-4).Conversely, when the external osmolyte concentration suddenly decreases, water will diffuse into the cell, causing it to swell and, in extreme conditions, lyse. This is where the mechanosensitive channels are thought to play a role by opening in response to the increased membrane tension effected by the rapid increase in cell volume. The best known example of a channel in this role is the mechanosensitive channel of large conductance from Escherichia coli (MscL Ec ), but homologues are present in most eubacteria (5-7). MscL opens near the lytic tension limit of the bacterial membrane. A second mechanosensitive channel, that of small conductance, MscS, has been characterized in only a few organisms (8,9). MscS opens at lower membrane tensions and has a smaller conductance than MscL, making it useful for fine regulation of internal compatible...

show abstract

“…protein complexes of approximately 6.5 kDa are able to pass through the open MscL pore unhindered (2,17,151). The channel activates in response to changes in membrane tension without the aid of other components and is highly stable, as shown in the conservation of its gating functionality after purification and reconstitution into lipid vesicles (58).…”

Section: Mechanosensitive Channelsmentioning

confidence: 99%

Bacterial Mechanosensitive Channels: Models for Studying Mechanosensory Transduction

Martinac

Nomura

Chi

et al. 2014

Antioxidants & Redox Signaling

View full text Add to dashboard Cite

Significance: Sensations of touch and hearing are manifestations of mechanical contact and air pressure acting on touch receptors and hair cells of the inner ear, respectively. In bacteria, osmotic pressure exerts a significant mechanical force on their cellular membrane. Bacteria have evolved mechanosensitive (MS) channels to cope with excessive turgor pressure resulting from a hypo-osmotic shock. MS channel opening allows the expulsion of osmolytes and water, thereby restoring normal cellular turgor and preventing cell lysis. Recent Advances: As biological force-sensing systems, MS channels have been identified as the best examples of membrane proteins coupling molecular dynamics to cellular mechanics. The bacterial MS channel of large conductance (MscL) and MS channel of small conductance (MscS) have been subjected to extensive biophysical, biochemical, genetic, and structural analyses. These studies have established MscL and MscS as model systems for mechanosensory transduction. Critical Issues: In recent years, MS ion channels in mammalian cells have moved into focus of mechanotransduction research, accompanied by an increased awareness of the role they may play in the pathophysiology of diseases, including cardiac hypertrophy, muscular dystrophy, or Xerocytosis. Future Directions: A recent exciting development includes the molecular identification of Piezo proteins, which function as nonselective cation channels in mechanosensory transduction associated with senses of touch and pain. Since research on Piezo channels is very young, applying lessons learned from studies of bacterial MS channels to establishing the mechanism by which the Piezo channels are mechanically activated remains one of the future challenges toward a better understanding of the role that MS channels play in mechanobiology. Antioxid. Redox Signal. 00, 000-000.

show abstract

Release of Thioredoxin via the Mechanosensitive Channel MscL during Osmotic Downshock of Escherichia coli Cells

Cited by 148 publications

References 40 publications

C Termini of the Escherichia coli Mechanosensitive Ion Channel (MscS) Move Apart upon the Channel Opening

C Termini of the Escherichia coli Mechanosensitive Ion Channel (MscS) Move Apart upon the Channel Opening

Lactococcus lactis Uses MscL as Its Principal Mechanosensitive Channel

Bacterial Mechanosensitive Channels: Models for Studying Mechanosensory Transduction

Contact Info

Product

Resources

About