Researchers at the U have released a study that says protons can act like complex neurotransmitters, communicating signals to parts of the body. The discovery about the complex action of a fundamental particle came from research on how worms, namely nematodes, defecate.
The study was published in the January issue of the journal Cell. The original intent was not to name protons as another transmitter, but to gain understanding of the complex way that worms defecate. The desire among the researchers to understand how worms defecate sparked from an interest in similarities among animals.
"Eating, moving, having sex and pooping are common things that all animals do," said Wayne Davis, study co-author and a research assistant professor of biology, in a written statement.
Erik Jorgensen, a biology professor and the senior author of the study, said researchers continued with the study because of "a desire to understand how neural circuits function."
"What gears your body in motion? What animates creatures? How is it that you can think and act?" Jorgensen asked. "I guess, at a very basic level, because of a desire to understand the physical underpinnings of the world that we see around us."
Nematodes' intestinal systems are complex. Every 50 seconds a worm has a muscle contraction that results in defecation.
"We were interested in tearing apart the components required for (that) clock function," said Paola Nix, a graduate student who helped conduct the study, in a written statement. "To do that, we searched for mutations that affected the (defecation) clock."
Worms were exposed to chemicals to change their DNA sequence. The worms with the mutated DNA sequence had a difficult time defecating. Constipation in the worms was traced back to the mutation of two genes, pbo-4 and pbo-5.
The pbo-4 gene's main function is the production of a protein that pumps protons out of the intestine and into a fluid-filled space near the surrounding muscle. The pbo-5 gene also produces a protein, which is used as a receptor on the muscle around the gut. The protons that are pumped out of the intestine bind to the receptor protein, which causes the receptors to open and form a hole in the muscle cell. The hole allows ions to flow in, which makes the muscle contract.
Researchers also proved that protons were being pumped into the fluid-filled space outside of the intestines. Worms were bred with a green protein that loses its color when several ions are present. Under a microscope, the fluid became less green, which proved that ions were being pumped.
In the next experiment, researchers added ions into the worms. The result was the contraction of the intestinal muscles, proving that protons were acting like neurotransmitters and carrying the signal for the muscle to contract.
"This is the first time we have found protons acting as transmitters," Davis said in a written statement.
Nematodes are tiny worms composed of about 1,000 cells and are a good model for studying human biology because of similar tissue.
"It could be that these processes occur in humans. There are proton pumps present in intestinal cells and in the brain of humans and mice," Davis said. "Some of the pumps are thought to make acid for the gut to digest food."
d.posselli@chronicle.utah.edu
