title: The influence of static magnetic fields on mechanosensitive ion channel activity in artificial liposomes.
abstract: The influence of static magnetic fields (SMFs) on the activity of recombinant mechanosensitive ion channels (the bacterial mechanosensitive ion channel of large conductance-MscL) following reconstitution into artificial liposomes has been investigated. Preliminary findings suggest that exposure to 80-mT SMFs does not induce spontaneous MscL activation in the absence of mechanical stimulation. However, SMFs do appear to influence the open probability and single channel kinetics of MscL exposed to negative pipette pressure. Typical responses include an overall reduction in channel activity or an increased likelihood of channels becoming "trapped open" in sub-conducting states following exposure to SMFs. There is a delay in the onset of this effect and it is maintained throughout exposure. Generally, channel activity showed slow or limited recovery following removal of the magnetic field and responses to the magnetic were often reduced or abolished upon subsequent exposures. Pre-exposure of the liposomes to SMFs resulted in reduced sensitivity of MscL to negative pipette pressure, with higher pressures required to activate the channels. Although the mechanisms of this effect are not clear, our initial observations appear to support previous work showing that the effects of SMFs on ion channels may be mediated by changes in membrane properties due to anisotropic diamagnetism of lipid molecules.
authors.affiliation: Medical Research Unit, Institute of Science and Technology in Medicine, Keele University, Thornburrow Drive, Hartshill, Stoke-on-Trent, Staffordshire, ST4 7QB, UK. findstevenhughes@hotmail.com
authors.forename: Steven
authors.initials: S
authors.lastname: Hughes
authors.forename: Alicia J
authors.initials: AJ
authors.lastname: El Haj
authors.forename: Jon
authors.initials: J
authors.lastname: Dobson
authors.forename: Boris
authors.initials: B
authors.lastname: Martinac
mesh_terms: D016880:Anisotropy; D004574:Electromagnetic Fields; D004594:Electrophysiology; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism / Q000502:physiology*; D007477:Ions; D007700:Kinetics; D008055:Lipids / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry*; D008280:Magnetics; D018408:Patch-Clamp Techniques; D011312:Pressure; D011994:Recombinant Proteins / Q000737:chemistry; D013997:Time Factors
chemical_list: D029968:Escherichia coli Proteins; D007473:Ion Channels; D007477:Ions; D008055:Lipids; D008081:Liposomes; C086596:MscL protein, E coli; D011994:Recombinant Proteins; D005982:Glutathione Transferase