Peptide Patrols The Gut

An antimicrobial peptide released by cells lining the intestines is responsible for policing the bacteria that reside there, according to a team led by immunologist Lora V. Hooper of the University of Texas Southwestern Medical Center (Science, DOI: 10.1126/science.1209791). Biologists have known that there is an approximately 50-µm-thick, mucus-filled “demilitarized zone” protecting the gut from bacterial attack, Hooper says. But according to microbiome expert Peter J. Turnbaugh of Harvard University, the new study “makes a major stride toward understanding the mechanism responsible for this phenomenon and its potential impact on health and disease.” When Hooper and her colleagues removed the genes coding for the peptide—called RegIIIγ—from mice, they saw that rodent gut bacteria infiltrated the microbe-free zone, moving all the way to the intestinal tissue. Hooper says intestinal cells release RegIIIγ, which kills gram-positive bacteria, when a signaling protein called MyD88 sounds the alarm of invasion. The next step, she adds, is to figure out whether other policing peptides exist and to find ways of boosting RegIIIγ production for patients with gastrointestinal infection and disease.