Current Topics in Membranes provides a systematic, comprehensive, and rigorous approach to specific topics relevant to the study of cellular membranes. Each volume is a guest edited compendium of membrane biology. This series has been a mainstay for practicing scientists and students interested in this critical field of biology. Articles covered in the volume include The Mechanical Properties of Bilayers; Molecular Dynamic Modeling of MS Channels; Structures of the Prokaryotic Mechanosensitive; Channels MscL and MscS; 3. 5 Billion Years of Mechanosensory Transduction: Structure and Function of Mechanosensitive Channels in Prokaryotes; Activation of Mechanosensitive Ion Channels by Forces Transmitted through Integrins and the Cytoskeleton; Thermodynamics of Mechanosensitivity; Flexoelectricity and Mechanotransduction; Lipid Effects on Mechanosensitive Channels; Functional Interactions of the Extracellular Matrix with Mechanosensitive Channels; MSCL: The Bacterial Mechanosensitive Channel of Large Conductance; The Bacterial Mechanosensitive Channel MscS: Emerging Principles of Gating and Modulation; Structure function relations of MscS; The MscS Cytoplasmic Domain and its Conformational Changes upon the Channel Gating; Microbial TRP Channels and Their Mechanosensitivity; MSCS-Like Proteins in Plants; Delivering Force and Amplifying Signals in Plant Mechanosensing; MS Channels in Tip Growing Systems.
Inhaltsverzeichnis
1;Cover;1 2;Contents;6 3;Contributors;12 4;Foreword;16 5;Previous Volumes in Series;18 6;Chapter 1: Structures of the Prokaryotic Mechanosensitive Channels MscL and MscS;21 6.1;I. Overview;21 6.2;II. Introduction;22 6.3;III. Conductances of MscL and MscS: General Considerations;23 6.4;IV. Structure Determination of MscL and MscS;26 6.4.1;A. General Considerations in Membrane Protein Crystallography;26 6.4.2;B. Crystallographic Analysis of MscL and MscS;29 6.5;V. MscL and MscS Structures;31 6.6;VI. The Permeation Pathway in MscL and MscS;35 6.7;VII. Disulfide Bond Formation in MscL;37 6.8;VIII. Concluding Remarks;38 6.9;Acknowledgments;40 6.10;References;40 7;Chapter 2: 3.5 Billion Years of Mechanosensory Transduction: Structure and Function of Mechanosensitive Channels in Prokaryotes;45 7.1;I. Overview;46 7.2;II. Introduction;46 7.3;III. Discovery, Mechanism, and Structure of MS Channels in Prokaryotes;48 7.3.1;A. Historical Perspective;48 7.3.2;B. Conductance, Selectivity, and Activation by Membrane Tension of Bacterial MS Channels;48 7.3.3;C. Cloning of MscL and MscS of E. coli;50 7.3.4;D. Molecular Identification of MS Channels in Archaea;53 7.3.5;E. Molecular Structure of Prokaryotic MS Channels;55 7.3.6;F. Bilayer Mechanism and Gating by Mechanical Force;59 7.3.7;G. Spectroscopic Studies;61 7.3.8;H. Structural Models of Gating in MscL and MscS;63 7.4;IV. Pharmacology of Prokaryotic MS Channels;64 7.5;V. Families of Prokaryotic MS Channels;65 7.5.1;A. MscL Family;66 7.5.2;B. MscS Family;66 7.6;VI. Early Origins of Mechanosensory Transduction;66 7.6.1;A. Physiological Function of MS Channels in Prokaryotic Cells;67 7.6.2;B. Function of MscS-Like Channels in Mechanosensory Transduction in Plants;69 7.7;VII. Concluding Remarks;70 7.8;Acknowledgments;70 7.9;References;70 8;Chapter 3: Activation of Mechanosensitive Ion Channels by Forces Transmitted Through Integrins and the Cytoskeleton;79 8.1;I. Overview;79 8.2;II. Introduction;80 8.3;III. Conventional Views of MS
Channel Gating;83 8.4;IV. Tensegrity-Based Cellular Mechanotransduction;86 8.5;V. Force Transmission Through Integrins in Living Cells;90 8.6;VI. Potential Linkages Between Integrins and MS Ion Channels;93 8.7;VII. Conclusions and Future Implications;97 8.8;References;98 9;Chapter 4: Thermodynamics of Mechanosensitivity;107 9.1;I. Overview;107 9.2;II. Introduction;108 9.2.1;A. General Equations;110 9.3;III. Area Sensitivity;111 9.3.1;A. Line Tension and Area Sensitivity;113 9.3.2;B. Direct Observations of the Effect of Line Tension and Shape Transformation;116 9.4;IV. Shape Sensitivity;119 9.4.1;A. Experimental Observation of Shape Sensitivity;120 9.5;V. Length Sensitivity and Switch Between Stretch-Activation and Stretch-Inactivation Modes;123 9.5.1;A. Channel Activation by LPLs;128 9.5.2;B. Other Parameters Regulating Switch Between Stretch-Activation and Inactivation Modes;131 9.6;VI. Thermodynamic Approach and Detailed Mechanical Models of MS Channels;132 9.6.1;A. Detailed Mechanical Models;133 9.7;VII. Conclusions;134 9.8;References;135 10;Chapter 5: Flexoelectricity and Mechanotransduction;141 10.1;I. Overview;141 10.2;II. Introduction;141 10.3;III. Flexoelectricity, Membrane Curvature, and Polarization;142 10.3.1;A. Flexoelectricity and Membrane Lipids;144 10.3.2;B. Flexoelectricity and Membrane Proteins;150 10.4;IV. Experimental Results on Flexoelectricity in Biomembranes;151 10.4.1;A. Theoretical Remarks;151 10.4.2;B. Experimental Data;152 10.5;V. Flexoelectricity and Mechanotransduction;163 10.6;VI. Conclusions;167 10.7;References;168 11;Chapter 6: Lipid Effects on Mechanosensitive Channels;171 11.1;I. Overview;171 11.2;II. Intrinsic Membrane Proteins;172 11.3;III. Effects of Lipid Structure on Membrane Protein Function;172 11.4;IV. How to Explain Effects of Lipid Structure on Membrane Protein Function;175 11.4.1;A. The Lipid Annulus;175 11.4.2;B. The Fluidity of a Lipid Bilayer and Its Consequences;176 11.4.3;C. The Importance of Hydrophobic Thickness;183
11.4.4;D. Curvature Stress;186 11.4.5;E. Elastic Strain and Pressure Profiles;188 11.4.6;F. General Features of Lipid-Protein Interactions;190 11.5;V. What Do These General Principles Tell Us About MscL?;191 11.6;References;194 12;Chapter 7: Functional Interactions of the Extracellular Matrix with Mechanosensitive Channels;199 12.1;I. Overview;199 12.2;II. Mechanotransduction;200 12.3;III. Mechanosensitive Channels in Connective Tissue Cells;202 12.4;IV. The Extracellular Environment of Cells;204 12.5;V. Force Transmission from Matrix to Cytoskeleton;207 12.5.1;A. Focal Adhesions;207 12.5.2;B. Selectins;208 12.6;VI. Experimental Models of Force Application to Connective Tissue Cells;209 12.7;VII. Effects of Force on Cell Surface Structures;213 12.8;VIII. Future Approaches;214 12.9;References;215 13;Chapter 8: MscL: The Bacterial Mechanosensitive Channel of Large Conductance;221 13.1;I. Overview;222 13.2;II. Introduction and Historical Perspective;222 13.2.1;A. The Discovery of MS Channels in Bacteria;222 13.2.2;B. Proposing a Function;223 13.2.3;C. The Identification of Multiple MS Channel Activities in E. coli;223 13.2.4;D. Identification of the E. coli mscL Gene;225 13.2.5;E. Early Mutagenesis Studies;226 13.3;III. A Detailed Structural Model: An X-Ray Crystallographic Structure from an E.coli MscL Orthologue;227 13.3.1;A. The Crystal Structure;228 13.3.2;B. Fitting the Structure with the Findings from Mutagenesis Studies;229 13.3.3;C. Comparing Tb-MscL with Eco-MscL;230 13.4;IV. Proposed Models for How the MscL Channel Opens;232 13.4.1;A. Opening the Channel: Twist and Turn;232 13.4.2;B. Molecular Dynamic Simulations;242 13.5;V. Physical Cues for MscL Channel Gating: Protein-Lipid Interactions;243 13.5.1;A. Studies of the Energetic and Spatial Parameters for MscL Gating;243 13.5.2;B. Does MscL Sense the Pressure Across the Membrane or the Tension Within It?;244 13.5.3;C. Sensing the Biophysical Properties of the Membrane;244 13.5.4;D. Specific Protein-Lipid Inte
ractions;245 13.6;VI. MscL as a Possible Nanosensor;247 13.7;VII. Conclusions;248 13.8;Acknowledgments;248 13.9;References;249 14;Chapter 9: The Bacterial Mechanosensitive Channel MscS: Emerging Principles of Gating and Modulation;255 14.1;I. Overview;256 14.2;II. Introduction;256 14.3;III. MscS and Its Relatives;258 14.3.1;A. A Brief Account of Bacterial Osmoregulation and the Discovery of MscS;258 14.3.2;B. MscS Vs MscK: How to Interpret Early Functional Data?;260 14.3.3;C. Purification and Reconstitution of MscS Showed Homo-Multimeric Channels Activated by Tension in the Lipid Bilayer;262 14.4;IV. Structural and Computational Studies;262 14.4.1;A. Structure of MscS and First Hypotheses About Its Gating Mechanism;262 14.4.2;B. Computational Studies of MscS;264 14.5;V. Functional Properties of MscS;269 14.5.1;A. MscS Conduction and Selectivity;269 14.5.2;B. Gating Characteristics of MscS In Situ;270 14.5.3;C. Mutations That Affect MscS Activity;272 14.5.4;D. MscS Inactivation;273 14.6;VI. What Do the Closed, Open, and Inactivated States of MscS Look Like?;276 14.6.1;A. Is the Crystal Structure a Native State?;277 14.6.2;B. Closed State;278 14.6.3;C. Open State;278 14.7;VII. Emerging Principles of MscS Gating and Regulation and the New Directions;280 14.8;References;283 15;Chapter 10: StructureFunction Relations of MscS;289 15.1;I. Overview;289 15.2;II. Introduction;290 15.2.1;A. Functional Overview;293 15.3;III. The Structure of MscS;296 15.3.1;A. The Membrance Domain;298 15.3.2;B. The Cytoplasmic Domain;298 15.3.3;C. Variations in Structure;299 15.3.4;D. Twisting MscS Around the Pore;300 15.3.5;E. MscS Is Small but Beautifully Formed;301 15.4;IV. MscS Mutational Analysis;302 15.5;V. Structural Transitions in MscS;304 15.5.1;A. The Need for the Closed State;304 15.5.2;B. The Crystal State;305 15.5.3;C. The TM3 Pore;307 15.5.4;D. The Closed-to-Open Transition;308 15.6;VI. Conclusions and Future Perspective;311 15.7;Acknowledgments;311 15.8;References;312 16;Chapter
11: The MscS Cytoplasmic Domain and Its Conformational Changes on the Channel Gating;315 16.1;I. Overview;315 16.2;II. MscL and MscS: Primary Gates and Similarities in Activation;316 16.3;III. The MscL Cytoplasmic Regions and Functioning of the Channel;319 16.4;IV. The MscS C-Terminal Chamber: The Cage-Like Structure and Kinetics;320 16.5;V. Structural Alterations of the MscS Cytoplasmic Chamber on Gating;323 16.6;VI. Conclusions and Perspectives;325 16.7;Acknowledgments;326 16.8;References;326 17;Chapter 12: Microbial TRP Channels and Their Mechanosensitivity;331 17.1;I. Overview;331 17.2;II. A History TRP-Channel Research;332 17.3;III. The Mechanosensitivity of Animal TRP Channels;333 17.4;IV. Distribution and the Unknown Origin of TRPs;334 17.5;V. TRPY1: The TRP Channel of Budding Yeast;337 17.6;VI. Other Fungal TRP Homologues;341 17.7;VII. Sequence Information Does Not Explain TRP Mechanosensitivity;342 17.8;VIII. Conclusions;343 17.9;Acknowledgment;344 17.10;References;344 18;Chapter 13: MscS-Like Proteins in Plants;349 18.1;I. Overview;349 18.2;II. Mechanosensation and Ion Channels in Plants;350 18.2.1;A. Plants Cells and Turgor Pressure;350 18.2.2;B. Mechanosensory Signal Transduction in Plants;351 18.2.3;C. MS Ion are Present in Plant Cell Membranes;353 18.3;III. The Eukaryotic Family of MscS_Like Proteins;357 18.3.1;A. E. coil MscS;357 18.3.2;B. The Eukaryotic Subfamily;359 18.4;IV. The Arabidopsis MSL Genes;365 18.4.1;A.Overview;365 18.4.2;B. Subcellular Localization of MSL Proteins;367 18.4.3;C. Control of MSL Gene Expression;368 18.4.4;D. MSL2, MSL3, and the Control of Organelle Morphology;369 18.5;V. Outstanding Questions;371 18.5.1;A. How Have MscS-Like Proteins Evolved?;371 18.5.2;B. What Roles Do MS Ion Channels Play in Plant Biology?;371 18.5.3;C. Is Clustering of MS Ion Channels Important?;372 18.6;V. Conculsion;373 18.7;References;373 19;Chapter 14: Delivering Force and Amplifying Signals in Plant Mechanosensing;381 19.1;I. Overview;382 19.2;II. I
ntroduction;382 19.3;III. Focusing Force;385 19.3.1;A. Force Experienced by a Plant Is Chiefly Borne by the Heterogeneous Wall System;385 19.3.2;B. The Plasmalemmal Reticulum Carries Force to the Channels;386 19.3.3;C. Implication of Heterogeneous Walls for Thigmotropic Reception;392 19.3.4;D. Walls Are Only Half the Mechanical Story: Gravitropism, Like Plant Form, Depends on Force Generated Inside Cells;392 19.3.5;E. Not Just Any Displacement Triggers Gravitropism;396 19.3.6;F. Map of Mechanotropic Cells in the Root Cap;396 19.4;IV. Transduction and Ensuing Events in Thigmotropism;398 19.5;V. Early Events in Gravitropism;399 19.5.1;A. Direct Evidence for Pulsed Ca2+ Elevation;399 19.5.2;B. Curvature Kinetics Are Consistent with MCaCs as Gravitropic Transducers;400 19.5.3;C. Ca2+ Kinetics and Xenobiotic Effects Are Consistent with MCaCs as Gravitropic Transducers;401 19.5.4;D. Ramping Sensitivity Up and Down Again: Voltage and pH Modulation of MCaCs;403 19.5.5;E. Variable Linkage: A "Nonmechanical" Role for the PR;404 19.5.6;F. Cloistering Ca2+;404 19.6;VI. From Primary Transduction Pulse Forward: Facilitative and Vectorial Gravitropic Reception;405 19.6.1;A. Facilitative Gravitropic Reception;406 19.6.2;B. Vectorial Gravitropic Reception;406 19.6.3;C. Decay of Facilitative Reception;408 19.7;VII. What Comes Next;409 19.8;References;410 20;Chapter 15: MS Channels in Tip-Growing Systems;413 20.1;I. Overview;413 20.2;II. Introduction;414 20.3;III. Lilium longiflorum Pollen Tubes;415 20.4;IV. Saprolegnia ferax Hyphae;420 20.5;V. Silvetia compressa Rhizoids;422 20.6;VI. Neurospora crassa Hyphae;425 20.7;VII. Is Turgor Necessary for Activation of MS Channels?;426 20.8;VIII. Conclusions;427 20.9;References;429 21;Index;433
