ABSTRACT
Most prokaryotic and eukaryotic cells have the ability to sense and respond to alterations in various mechanical stimuli. This is most apparent in higher organisms (eukaryotic cells), which have developed sensory systems with specialized sensory cells for detecting a wide range of stimuli including mechanical distortions of the cell membrane. However, the basic mechanisms of sensing (mechanosensation) and
16.1 Introduction .................................................................................................. 353 16.1.1 Osmomechanical Sensing and Transduction .................................... 353 16.1.2 Osmomechanical-Sensitive TRP Channels ...................................... 354 16.1.3 Mechanisms of Channel Activation by
Osmomechanical Stresses ................................................................ 356 16.2 Osmomechanical Regulation of TRP Channels ........................................... 356
16.2.1 Assessing the Activity of Calcium-Permeable TRP Channels ......... 356 16.2.1.1 Patch-Clamp Techniques ................................................... 356 16.2.1.2 Calcium Imaging ............................................................... 358 16.2.1.3 Channel Abundance and Localization ............................... 359
16.2.2 Osmotic Stress/Cell Volume .............................................................360 16.2.3 Shear Stress/Fluid Flow .................................................................... 363 16.2.4 Membrane Stretch/Cell Stretch ........................................................ 365
16.2.4.1 Stretch-Induced Stresses and Cell Injury........................... 365 16.2.4.2 Membrane Deformation Models ........................................366
16.3 Application of Osmomechanical Stresses: Practical Considerations ........... 368 16.3.1 Patch-Clamp versus Calcium Imaging Methods .............................. 368 16.3.2 Cell Adhesion ................................................................................... 369
16.4 Conclusions ................................................................................................... 369 Acknowledgments .................................................................................................. 370 References .............................................................................................................. 370
transducing (mechanotransduction) mechanical stimuli are apparent throughout evolutionary biology with bacteria already displaying mechanosensitive channels that are activated in response to osmotic stimuli (hyperosmolarity).1-3 Mechanosensitive channel opening in these prokaryotes is induced upon the generation of tension within the cell membrane. In eukaryotes, much more elaborate systems of mechanosensation have been developed in association with the evolution of an extensive scaffolding network, the actin cytoskeleton, with sites of tethering to the plasma membrane and to external sites through integrin-extracellular matrix attachments.4-6 As a result, changes in cell volume, shape, or tension within the cell membranes can rapidly lead to induction of ion channels or biochemical cascades as part of the transduction process.
