title: Differential effects of lipids and lyso-lipids on the mechanosensitivity of the mechanosensitive channels MscL and MscS.
abstract: 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.
authors.affiliation: Molecular Cardiology and Biophysics Divison/Mechanosensory Biophysics Laboratory, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010,  Australia.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nomura
authors.forename: Charles G
authors.initials: CG
authors.lastname: Cranfield
authors.forename: Evelyne
authors.initials: E
authors.lastname: Deplazes
authors.forename: Dylan M
authors.initials: DM
authors.lastname: Owen
authors.forename: Alex
authors.initials: A
authors.lastname: Macmillan
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Battle
authors.forename: Maryrose
authors.initials: M
authors.lastname: Constantine
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sokabe
authors.forename: Boris
authors.initials: B
authors.lastname: Martinac
mesh_terms: D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D029968:Escherichia coli Proteins / Q000378:metabolism / Q000502:physiology*; D031541:Fluorescence Resonance Energy Transfer; D007473:Ion Channels / Q000378:metabolism / Q000502:physiology*; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008055:Lipids / Q000737:chemistry* / Q000494:pharmacology; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008246:Lysophospholipids / Q000737:chemistry / Q000494:pharmacology; D040542:Mechanotransduction, Cellular / Q000187:drug effects / Q000502:physiology*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D018408:Patch-Clamp Techniques; D010713:Phosphatidylcholines / Q000737:chemistry / Q000494:pharmacology; D013104:Spheroplasts / Q000187:drug effects / Q000378:metabolism / Q000502:physiology
chemical_list: D029968:Escherichia coli Proteins; D007473:Ion Channels; D008051:Lipid Bilayers; D008055:Lipids; D008081:Liposomes; D008246:Lysophospholipids; C086596:MscL protein, E coli; C469542:MscS protein, E coli; D010713:Phosphatidylcholines; C024990:asolectin