Hidden mechanism of swallowing revealed by Caenorhabditis elegans

When we eat, the digestive tract generates various signals that can be linked to important physiological processes. However, our understanding of how the movement and accumulation of food in the digestive tract are sensed and processed to regulate important food intake behaviors like swallowing remains limited.

Piezo channels are proteins that sense physical pressure or stimuli in the body. They are located in cell membranes and open when pressure or force is applied, allowing substances like calcium ions (Ca2+) to enter the cells. After entering, these ions send signals to the cells to trigger the body's response. For example, Piezo channels are involved in sensing a touch felt by skin, blood pressure, and lung and bladder expansion. In this study, the researchers found that in a Caenorhabditis elegans (C. elegans), which has a digestive tract structure like that of humans, the Piezo channels detect food accumulation in the digestive tract and trigger swallowing behavior.

The research team focused on the pharyngeal-intestinal valve in a C. elegans' digestive tract. This valve connects the pharynx to the intestine, regulates food movement routes, and has a structure similar to the human esophagus. The team discovered that Piezo channels are activated in this valve. When a C. elegans eats, the food accumulates at the front of the intestine. The Piezo channel then senses the pressure created by the expansion of the intestine and regulates the process of pushing the food down the intestine through a movement called a pharyngeal plunge.

For the first time in the world, Prof. Kim's team has identified the specific mechanism of how intestinal distension caused by food accumulation in the digestive system regulates food intake behavior, especially swallowing, at the molecular level in an organism.

"This study sheds light on the fundamental question about how the body's internal sensations regulate the physiological processes related to food intake," said Prof. Kim, corresponding author of the paper. He added, "We expect this study to provide important insights into the role of the digestive system in the food intake process and how these physiological processes are organically linked."

Ph.D. student Park Yeon-ji and Dr. Yeon Jihye of the Department of Brain Sciences are the co-first authors of this study, with Prof. Kim Kyuhyung being the corresponding author. The study was conducted in collaboration with the teams of Dr. Kang Kyungjin of the Korea Brain Research Institute and Dr. Lee Kyungeun of the Korea Institute of Science and Technology and published on November 21, 2024, in Nature Communications, a top-tier journal in the field of biology.