London: Like sensors in a bank vault, our cells too have their own early-warning system for intruders: deadly pathogens and viruses waiting to attack and infect us.
Scientists at the European Molecular Biology Lab (EMBL) in Grenoble, France, have unravelled how a particular protein sounds the alarm when it detects invading viruses.
The study advances our understanding of the innate immune response, shedding light on how cells rapidly respond to a wide range of viruses including flu, rabies and hepatitis, the journal Cell reports.
For the purpose, cells rely on proteins called pattern recognition receptors, which identify and bind to molecular signatures specific to the intruding or invading pathogens, according to an EMBL statement.
This binding subsequently 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. EMBL scientists have now discovered the precise structural mechanism by which one of these receptors, RIG-I, converts a change of shape into a signal.
"For a structural biologist this is a classic question: how does ligand binding to a receptor induce signalling," says Stephen Cusack, who led the work.
"We were particularly interested in answering it for RIG-I, as it targets practically all RNA viruses, including influenza, measles and hepatitis C," said Stephen Cusack from EMBL, who led the study.
In response to a viral infection, RIG-I recognises viral genetic material -- specifically, viral RNA -- and primes the cell to produce the key anti-viral molecule, interferon.
Interferon is secreted and picked up by surrounding cells, causing them to turn on hundreds of genes that act to combat the infection.