Worm Breeder's Gazette 16(1): 48 (October 1, 1999)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Identification of a Novel Mechanosensitive Anion Current in Embryonic Cells of C. elegans*

Michael Christensen, Kevin Strange

Anesthesiology Research Division, Departments of Anesthesiology and Pharmacology, Vanderbilt University, Nashville, Tennessee 37232-2520

Mechanotransduction plays a central role in fundamental physiologic processes such as detection of touch and sound, regulation of cell volume, and control of motility. Mechanosensitive channels have been studied extensively using electrophysiology. Little is known, however, about the molecular structure of mechanosensitive channels or about how mechanical stress is transduced into altered channel gating. We developed techniques to patch-clamp and study ion channels in C. elegans embryonic cells. In cell-attached and inside-out patches, application of gentle suction activated a mechanosensitive current. Suction caused an immediate increase in current amplitude of 6.4 2.8 fold (n = 20) at +100 mV in inside-out patches. The current rapidly inactivated when suction was discontinued and could be repeatedly reactivated by additional suction. When membrane voltage was ramped from +100 to -100 mV at 100 mV/second, the current showed moderate outward rectification (outward:inward current = 2.0 0.05 at 100 mV). Current amplitude was largely unaffected when bath Na+ was replaced with NMDG+ (n = 10). However, replacement of bath Cl- with either gluconate or glutamate reduced inward and outward currents by 46 10% and 39 7%, respectively (n = 9). Replacement of 120 mM bath Cl- with a mixture of 60 mM Cl- and 60 mM SCN- increased the inward current at -100 mV by 3.0 0.4 fold and shifted Erev by 16 2 mV (n=7). We conclude that membrane stretch activates a novel mechanosensitive anion current in inside-out patches from C. elegans embryonic cells.

C. elegans is the first metazoan organism for which the genome has been fully sequenced. The molecular and genetic techniques developed for study of this organism make it a powerful model system for molecular identification and characterization of ion transport pathways. Combining molecular biology techniques, genetic analysis, and electrophysiologic measurements provides us with a unique opportunity to identify the molecular components of a native eukaryotic mechanosensitive ion channel, to elucidate its role in cell function, and to define the molecular mechanisms by which force is transduced into channel activation. (Supported by NIH grants DK51610 and NS30591)

*This work will be presented at the 1999 annual meeting of the Society of General Physiologists. The abstract will be published in the July 1999 issue of the Journal of General Physiology.