Take it and release it: The use of the Rab1 small GTPase at a bacterium's will.

Successful pathogens are equipped to exploit the signaling pathways of their host cell to establish a niche conducive for their survival and proliferation. One emerging example is the modulation of the small GTPase Rab1 by virulence factors of the intracellular pathogen Legionella pneumophila. Besides proteins that mimic host regulatory factors involved in controlling Rab1 activity, this bacterium temporally locks this small GTPase in its active form by AMPylation. Efficient release of Rab1 from the bacterial phagosome requires deAMPylation prior to being inactivated by the bacterial GAP protein LepB. Whether Rab activity is similarly regulated under native condition is unknown, but it is clear that virulence factors from pathogens can be invaluable tools in dissecting the intricacy of host cellular processes.