Cell Cartoon

illustration by Leif Parsons

Immune Rally Cry

Like a Good Samaritan, a cell that’s been attacked by a virus warns neighboring cells to shore up their defenses. These alerts are sent via a family of proteins called interferons, which are produced when surveillance proteins in the infected cell detect a pathogen. Although several different surveillance proteins scout for signs of pathogens, new research shows how the proteins all activate a single molecule called IRF3 to turn on interferon production.

There are three known pathways that trigger type 1 interferon production. In each case, the individual pathway’s unique surveillance protein uses its own adaptor protein to relay the message that an invader is present and interferon is needed. Siqi Liu, a graduate student in HHMI Investigator Zhijian “James” Chen’s lab at the University of Texas Southwestern Medical Center, noticed that all three adaptor proteins have similar stretches of five amino acids that became tagged with phosphate groups. As the team reported March 13, 2015, in Science, the addition of a phosphate molecule to that stretch of amino acids causes the adaptors to activate IRF3.

Now that they know how the interferon pathways converge, Chen and his team are examining them in more detail. Eventually, they hope to develop small molecules that treat immune disorders by interfering with the pathways.