A SIXTH SENSE FOR RAB5 It has long been known that the mammalian small GTPase Rab5 is involved in clathrin-mediated endocytosis. However, most Rab5-interacting proteins are localized to

endosomes rather than to the plasma membrane. A newly discovered nucleotide-exchange factor for Rab5 in _Caenorhabditis elegans_ now provides the missing link for activating Rab5 at the

plasma membrane. * Alexander M. van der Bliek