Scientists Xueping Wang, Deidra M. Balchak, Clayton Gentilcore, Nathan L. Clark, and Ossama B. Kashlan from the University of Pittsburgh are presenting their research today on how sodium channels evolved as animals moved onto land at the 9th Aldosterone and ENaC in Health and Disease: The Kidney and Beyond Conference in Colorado.
Sodium channels found in epithelial cells (ENaCs) are very important in regulating salt and water balance especially in the kidneys, colon and lungs. The channel is made up of subunits that came about as a result of gene duplications at three points in evolutionary history. The first two duplication events coincided with the evolution of jawless fishes, such as lampreys, which have α, β, and γ subunits. Prior to migration onto land, the Δ subunit then evolved. The first species that was identified to have all 4 subunits is the lobe-finned coelacanth, which are thought to represent an early phase in the transition to four-legged terrestrial animals:
The ability to evolve these specialized sodium channels was important in the transition to land as the animals moved out of their salt water environment and faced new challenges in regulating salt and water balance. When the channels are created, the subunits can be altered, which can change the activity of the channel.