A protein has been identified that is responsible for detecting and controlling bacteria that escape some other host defense mechanisms. This protein seems to be involved in the eradication of several highly pathogenic bacteria, as reported in this week's Nature Immunology.
Although typically sequestered within an isolated compartment within the host cell, harmful bacteria including salmonella ― varieties of which can cause typhoid fever and gastroenteritis in humans ― occasionally escape this compartment and invade the host cell proper. For as yet undetermined reasons, these 'escapee' bacteria are often then coated with the host protein ubiquitin.
Felix Randow and colleagues found that the host protein NDP52 binds to these ubiquitin-coated bacteria and is required for the elimination of the invading bacteria. NDP52 seems to facilitate autophagy ― a type of engulfment ― of bacteria, by recruiting other host defense proteins. Additional work is needed to determine exactly how many varieties of pathogenic bacteria are controlled by NDP52.