A signaling protein known as STING is a critical player in the human immune system, detecting signs of danger within cells and then activating a variety of defense mechanisms.
STING is primarily on the lookout for DNA, which can indicate either a foreign invader such as a virus or damage to the host tissue or cell. When STING detects that danger signal, it can turn on at least three different pathways — one leading to interferon production, one to non-canonical autophagy (involved in recycling cell components and clearing pathogens), and a third to formation of the inflammasome, a complex of proteins that activates inflammatory responses. The mechanism by which STING stimulates interferon production is well characterized, but it has not been understood how it activates the other two processes.
Now, a team of MIT and Harvard Medical School researchers has discovered how STING activates those two pathways. They found that STING has a surprising and previously unknown function: It can act as an ion channel that allows protons to leak out of an organelle known as the Golgi body. This makes it the first human immune sensor that can translate danger signals into ion flow.
