When a thief breaks into a bank vault, sensors are activated and
the alarm is raised. Cells have their own early-warning system
for intruders, and scientists at the European Molecular Biology
Laboratory (EMBL) in Grenoble, France, have discovered how a
particular protein sounds that alarm when it detects invading
viruses. The study, published October 14 in Cell, is a key
development in our understanding of the innate immune response,
shedding light on how cells rapidly respond to a wide range of
viruses including influenza, rabies and hepatitis. To sense
invading agents, cells use proteins called pattern recognition
receptors, which recognise and bind to molecular signatures
carried only by the intruder. This binding causes the receptors
to change shape, starting a chain-reaction that ultimately
alerts the surrounding cells to the invasion. How these two
processes - sensing and signalling -- are connected, has until
now remained unclear. The EMBL scientists have now discovered
the precise structural mechanism