Current topics in membranes: Mechanosensitive Ion Channels: Part A

sdarticle_Vol & Auth......Page 1
sdarticle_v......Page 2
sdarticle_xi......Page 8
Foreword......Page 12
sdarticle_xvii......Page 14
Overview......Page 17
Introduction......Page 18
Conductances of MscL and MscS: General Considerations......Page 19
Source of Membrane Protein......Page 22
Purification......Page 23
Structure Determination......Page 24
Crystallographic Analysis of MscL and MscS......Page 25
MscL and MscS Structures......Page 27
The Permeation Pathway in MscL and MscS......Page 31
Disulfide Bond Formation in MscL......Page 33
Concluding Remarks......Page 34
References......Page 36
3.5 Billion Years of Mechanosensory Transduction: Structure and Function of Mechanosensitive Channels in Prokaryotes......Page 41
Introduction......Page 42
Conductance, Selectivity, and Activation by Membrane Tension of Bacterial MS Channels......Page 44
Cloning of MscL and MscS of E.coli......Page 46
Molecular Identification of MS Channels in Archaea......Page 49
Molecular Structure of Prokaryotic MS Channels......Page 51
Bilayer Mechanism and Gating by Mechanical Force......Page 55
Spectroscopic Studies......Page 57
Structural Models of Gating in MscL and MscS......Page 59
Pharmacology of Prokaryotic MS Channels......Page 60
Families of Prokaryotic MS Channels......Page 61
Early Origins of Mechanosensory Transduction......Page 62
Physiological Function of MS Channels in Prokaryotic Cells......Page 63
Function of MscS-Like Channels in Mechanosensory Transduction in Plants......Page 65
References......Page 66
Overview......Page 74
Introduction......Page 75
Conventional Views of MS Channel Gating......Page 78
Tensegrity-Based Cellular Mechanotransduction......Page 81
Force Transmission Through Integrins in Living Cells......Page 85
Potential Linkages Between Integrins and MS Ion Channels......Page 88
Conclusions and Future Implications......Page 92
References......Page 93
Overview......Page 101
Introduction......Page 102
General Equations......Page 104
Area Sensitivity......Page 105
Line Tension and Area Sensitivity......Page 107
Direct Observations of the Effect of Line Tension and Shape Transformation......Page 110
Shape Sensitivity......Page 113
Experimental Observation of Shape Sensitivity......Page 114
Length Sensitivity and Switch Between Stretch-Activation and Stretch-Inactivation Modes......Page 117
Channel Activation by LPLs......Page 122
Other Parameters Regulating Switch Between Stretch-Activation and Inactivation Modes......Page 124
Thermodynamic Approach and Detailed Mechanical Models of MS Channels......Page 125
Detailed Mechanical Models......Page 127
Conclusions......Page 128
References......Page 129
Introduction......Page 134
Flexoelectricity, Membrane Curvature, and Polarization......Page 135
Dipolar Flexoelectricity of Connected Bilayers: Blocked Lipid Exchange......Page 137
Flexoelectric Polarization and Transmembrane Voltage Difference......Page 138
Detailed Electric Neutrality......Page 139
Global Electric Neutrality......Page 141
Flexoelectricity and Membrane Proteins......Page 143
Theoretical Remarks......Page 144
Direct Flexoeffect of Native Membranes at Sine Pressure Excitation......Page 145
Direct Flexoeffect of Native Membranes at Pulsed Pressure Excitation......Page 148
Converse Flexoeffect of Native Membranes at Pulsed Electric Excitation......Page 149
Flexoelectricity in Channel-Containing Model and Native Membranes......Page 151
Flexoelectricity and Mechanotransduction......Page 156
Conclusions......Page 160
References......Page 161
Overview......Page 164
Effects of Lipid Structure on Membrane Protein Function......Page 165
The Lipid Annulus......Page 168
The Fluidity of a Lipid Bilayer and Its Consequences......Page 169
The Importance of Hydrophobic Thickness......Page 176
Curvature Stress......Page 179
Elastic Strain and Pressure Profiles......Page 181
General Features of Lipid-Protein Interactions......Page 183
What Do These General Principles Tell Us About MscL?......Page 184
References......Page 187
Overview......Page 192
Mechanotransduction......Page 193
Mechanosensitive Channels in Connective Tissue Cells......Page 195
The Extracellular Environment of Cells......Page 197
Focal Adhesions......Page 200
Selectins......Page 201
Experimental Models of Force Application to Connective Tissue Cells......Page 202
Effects of Force on Cell Surface Structures......Page 206
Future Approaches......Page 207
References......Page 208
MscL: The Bacterial Mechanosensitive Channel of Large Conductance......Page 213
The Discovery of MS Channels in Bacteria......Page 214
The Identification of Multiple MS Channel Activities in E. coli......Page 215
Identification of the E. coli mscL Gene......Page 217
Early Mutagenesis Studies......Page 218
A Detailed Structural Model: An X-Ray Crystallographic Structure from an E. coli MscL Orthologue......Page 219
The Crystal Structure......Page 220
Fitting the Structure with the Findings from Mutagenesis Studies......Page 221
Functional Comparisons......Page 222
Does the Structure Reflect a Fully Closed State?......Page 223
Opening the Channel: Twist and Turn......Page 224
Tilting the Transmembrane Domains......Page 225
Rotating TMD1......Page 227
A Closed-Expanded State......Page 229
Does the C-Terminal alpha-Helical Bundle Open?......Page 231
Role for the Periplasmic Loop......Page 232
Asymmetric Movements......Page 233
Molecular Dynamic Simulations......Page 234
Studies of the Energetic and Spatial Parameters for MscL Gating......Page 235
Sensing the Biophysical Properties of the Membrane......Page 236
Specific Protein-Lipid Interactions......Page 237
MscL as a Possible Nanosensor......Page 239
Acknowledgments......Page 240
References......Page 241
The Bacterial Mechanosensitive Channel MscS: Emerging Principles of Gating and Modulation......Page 246
Introduction......Page 247
A Brief Account of Bacterial Osmoregulation and the Discovery of MscS......Page 249
MscS Vs MscK: How to Interpret Early Functional Data?......Page 251
Structure of MscS and First Hypotheses About Its Gating Mechanism......Page 253
How Compact Is the Resting State of MscS?......Page 255
The Pore as Predicted by the Crystal Structure Is Largely Dehydrated......Page 256
Expansion Is Required to Promote Pore Hydration and Conduction......Page 258
MscS Conduction and Selectivity......Page 260
Gating Characteristics of MscS In Situ......Page 261
Mutations That Affect MscS Activity......Page 263
Parameters Affecting the Rate of Inactivation......Page 264
MscS Activity Depends on the Rate of Pressure Application......Page 265
Small Amphipathic Compounds Promote MscS Inactivation and Subunit Separation......Page 266
What Do the Closed, Open, and Inactivated States of MscS Look Like?......Page 267
Is the Crystal Structure a Native State?......Page 268
Open State......Page 269
Emerging Principles of MscS Gating and Regulation and the New Directions......Page 271
References......Page 274
Overview......Page 279
Introduction......Page 280
Functional Overview......Page 283
Expression of MS Channels......Page 284
MS Channel Function in Other Bacteria......Page 285
The Structure of MscS......Page 286
The Cytoplasmic Domain......Page 288
Variations in Structure......Page 289
Twisting MscS Around the Pore......Page 290
MscS Is Small but Beautifully Formed......Page 291
MscS Mutational Analysis......Page 292
The Need for the Closed State......Page 294
The Crystal State......Page 295
The TM3 Pore......Page 297
The Closed-to-Open Transition......Page 298
Acknowledgments......Page 301
References......Page 302
Overview......Page 305
MscL and MscS: Primary Gates and Similarities in Activation......Page 306
The MscL Cytoplasmic Regions and Functioning of the Channel......Page 309
The MscS C-Terminal Chamber: The Cage-Like Structure and Kinetics......Page 310
Structural Alterations of the MscS Cytoplasmic Chamber on Gating......Page 313
Conclusions and Perspectives......Page 315
References......Page 316
Overview......Page 320
A History TRP-Channel Research......Page 321
The Mechanosensitivity of Animal TRP Channels......Page 322
Distribution and the Unknown Origin of TRPs......Page 323
TRPY1: The TRP Channel of Budding Yeast......Page 326
Other Fungal TRP Homologues......Page 330
Sequence Information Does Not Explain TRP Mechanosensitivity......Page 331
Conclusions......Page 332
References......Page 333
Overview......Page 337
Plant Cells and Turgor Pressure......Page 338
Osmotic and Turgor Pressure......Page 339
Temperature......Page 340
MS Ion Channels Are Present in Plant Cell Membranes......Page 341
Introduction......Page 345
Important Features of MscS Sequence......Page 346
Class I and Class II Proteins......Page 347
Plant MscS-Like Proteins Are Likely to Form MS Ion Channels......Page 352
Overview......Page 353
Subcellular Localization of MSL Proteins......Page 355
Control of MSL Gene Expression......Page 356
MSL2, MSL3, and the Control of Organelle Morphology......Page 357
What Roles Do MS Ion Channels Play in Plant Biology?......Page 359
Is Clustering of MS Ion Channels Important?......Page 360
References......Page 361
Delivering Force and Amplifying Signals in Plant Mechanosensing......Page 368
Introduction......Page 369
Force Experienced by a Plant Is Chiefly Borne by the Heterogeneous Wall System......Page 372
The Plasmalemmal Reticulum Carries Force to the Channels......Page 373
Walls Are Only Half the Mechanical Story: Gravitropism, Like Plant Form, Depends on Force Generated Inside Cells......Page 379
An Electromechanical Pillow for the Channels......Page 380
Radial Reinforcement by the PR......Page 382
Map of Mechanotropic Cells in the Root Cap......Page 383
Transduction and Ensuing Events in Thigmotropism......Page 385
Direct Evidence for Pulsed Ca2+ Elevation......Page 386
Curvature Kinetics Are Consistent with MCaCs as Gravitropic Transducers......Page 387
Ca2+ Kinetics and Xenobiotic Effects Are Consistent with MCaCs as Gravitropic Transducers......Page 388
Ramping Sensitivity Up and Down Again: Voltage and pH Modulation of MCaCs......Page 390
Cloistering Ca2+......Page 391
From Primary Transduction Pulse Forward: Facilitative and Vectorial Gravitropic Reception......Page 392
Vectorial Gravitropic Reception......Page 393
Decay of Facilitative Reception......Page 395
What Comes Next......Page 396
References......Page 397
Overview......Page 400
Introduction......Page 401
Lilium longiflorum Pollen Tubes......Page 402
Saprolegnia ferax Hyphae......Page 407
Silvetia compressa Rhizoids......Page 409
Neurospora crassa Hyphae......Page 412
Is Turgor Necessary for Activation of MS Channels?......Page 413
Conclusions......Page 414
References......Page 416
sdarticle_413......Page 420