Summer heat too hot for you? What is co...( Extreme heat or cold is not only unc...)

Extreme heat or cold is not only uncomfortable, it can be deadlycausing proteins to unravel and malfunction.

For many years now, scientists have understood the molecular mechanisms that enable animals to sense dangerous temperatures; such as extremely high temperatures that directly trigger heat sensor proteins known as TRP channels. However, much more poorly understood is how animals sense very small temperature differences in the comfortable range, and choose their favorite temperature.

Reporting this week at Nature Neuroscience, Johns Hopkins researchers now have discovered that the fruit fly uses TRPA1 to sense single degree changes in the comfortable range. However, rather than sensing temperature changes directly, TRPA1 functions in the last step of a multistep process that uses many of the same proteins that function in vision. Just as the early events involved in vision allow animals to adapt to different light intensities, the multistep process involved in temperature detection potentially allows animals to adapt to different temperatures in the comfortable range as well.

"It's an exciting discovery, yet in a lot of ways it just makes a lot of sense," says Craig Montell, Ph.D., a professor of biological chemistry and member of Johns Hopkins' new Center for Sensory Biology. "You clearly don't want to hang around or adapt to a temperature that could kill you, but on the other hand, if you can't find your favorite temperature, it is OK to adapt to another comfortable temperature."

Montell and his team use fruit flies as their experimental model because it is easy to perform genetic manipulations on these animals. Temperatures colder than 16 degrees Celsius (61 degrees Fahrenheit) or warmer than 26 degrees C (79 degrees F) are known to trigger an avoidance response. Fruit fly maggots (larvae), explains Montell, prefer 18 degrees C (64 degrees F), but are comfortable at temperatures ranging from 18 to 24 degre
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