Findings may provide insight into biological basis of inner ear function and sense of touch
Researchers at the Howard Hughes Medical Institute and Rockefeller University have identified a molecule in vertebrates that senses osmotic pressure -- the measure of saltiness essential for living cells -- and may provide an inroad into understanding inner ear function and the sense of touch. The findings are reported in the October 27 issue of Cell.
The molecule, called VR-OAC (Vanilloid Receptor-related Osmotically Activated Channel), is an ion channel that responds to changes in osmotic pressure of extracellular fluid. Osmotic pressure is the pressure exerted by salts and proteins dissolved in bodily fluids. When osmotic pressure outside a cell decreases, this leads to an increased tension in a cell's membrane, like the tension in a balloon as it is inflated, a physical stimulus which in turn opens up the channel, allowing ions, among them calcium ions, to pass through, which elicits a cascade of intracellular events. In the case of sensory cells and nerve cells, this is converted into electrical signals to the central nervous system. The scientists cloned VR-OAC from rat, mouse, chicken and human gene libraries. The ion channel was detected in cells from the inner ear, the osmoregulator centers of the brain in the hypothalamus and from cells surrounding whiskers, a rodent's snout hair known to be very sensitive to touch. The presence of VR-OAC in the latter cells suggests that this receptor may also be involved in the sense of touch.
The research was led by Wolfgang Liedtke, M.D., a research associate in the Laboratory of Molecular Genetics headed by Jeffrey M. Friedman, M.D., Ph.D., an investigator at the Howard Hughes Medical Institute, and Stefan Heller, Ph.D., a former postdoctoral researcher in the Laboratory of Sensory Neuroscience at Rockefeller headed by A. James Hudspeth, M.D., Ph.D., also an investigator at the Howard
Contact: Joseph Bonner