Rab7 and Rab9 are members of the Ras superfamily of small Rab GTPases (1). Both proteins are located in late endosomes, but exert different functions. Rab7 associates with the RIPL effector protein to control membrane trafficking from early to late endosome and to lysosomes (2,3). Rab7 also helps to regulate growth receptor endocytic trafficking and degradation (3,4), and maturation of phagosome and autophagic vacuoles (4-6). Rab9 interacts with its effector proteins p40 and TIP47 (7,8) to promote the MPR (mannose 6-phosphate receptor)-associated lysosomal enzyme transport between late endosomes and the trans Golgi network (9,10).
