Biological complexity: sensing cold (Introduction)

by David Turell , Saturday, August 31, 2019, 18:42 (1911 days ago) @ David Turell

All organisms do it roughly the same way with the same specific protein receptors:

https://www.sciencedaily.com/releases/2019/08/190829150803.htm

"When environmental temperatures drop to uncomfortable, and even dangerous levels, receptor proteins within the sensory nerves in the skin perceive the change, and they relay that information to the brain. This is true for organisms from humans all the way down to the tiny, millimeter-long worms that researchers study in Xu's lab at the Life Sciences Institute: the model system Caenorhabditis elegans.

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"The researchers found that worms missing the glutamate receptor gene glr-3 no longer responded when temperatures dipped below 18 degrees Celsius (64 F). This gene is responsible for making the GLR-3 receptor protein. Without this protein, the worms became insensitive to cold temperatures, indicating that the protein is required for the worms to sense cold.

"What's more, the glr-3 gene is evolutionarily conserved across species, including humans. And it turns out the vertebrate versions of the gene can also function as a cold-sensing receptor.
When the researchers added the mammalian version of the gene to mutant worms lacking glr-3 -- and were thus insensitive to cold -- they found that it rescued the worms' cold sensitivity.

"They also added the worm, zebrafish, mouse and human versions of the genes to cold-insensitive mammalian cells. With all versions of the gene, the cells became sensitive to cold temperatures.

"The mouse version of the gene, GluK2 (for glutamate ionotropic receptor kainate type subunit 2), is well known for its role in transmitting chemical signals within the brain. The researchers discovered, however, that this gene is also active in a group of mouse sensory neurons that detect environmental stimuli, such as temperature, through sensory endings in the animals' skin.

"Reducing the expression of GluK2 in mouse sensory neurons suppressed their ability to sense cold, but not cool, temperatures. The findings provide additional evidence that the GluK2 protein serves as a cold receptor in mammals.

"'For all these years, attention has been focused on this gene's function in the brain. Now, we've found that it has a role in the peripheral sensory system, as well," Xu said. "It's really exciting. This was one of the few remaining sensory receptors that had not yet been identified in nature.'"

Comment: As usual the question is how did a chance evolutionary process find these exact proteins with their exact functions? Only design fits.