That protein, STIM1, was previously known to sense a change in calcium within immune cells, a process that occurs when the body confronts a pathogen. Upon sensing this change, STIM1 opens a type of pore in the cell membrane, called a CRAC channel, to allow the flow of calcium ions — a vital step in activating the immune system.
“People have generally thought that selectivity of ion channels is fixed and that selectivity and opening are separate processes; this is a fundamental shift in the way scientists believe ion channels operate,” says Prakriya, referring to the ‘pores’ that STIM1 regulates. “CRAC channels and STIM1 are absolutely vital to activating the immune system. As is observed in some human patients, you can block key parts of the system by blocking these molecules in immune cells. These finding reveal not only a novel mechanism by which CRAC channels operate, but also new ways in which it encodes biological information. This represents exciting new possibilities to develop therapeutics to treat a broad range of conditions.”