The Rab Family Antibody Sampler Kit provides an economical means to evaluate the presence and status of Rab proteins in cells. This kit provides enough primary and secondary antibodies to perform two Western blot experiments per primary antibody.

Rab family proteins are GTPases and members of the Ras superfamily of monomeric G proteins. These membrane-associated proteins are involved in many aspects of vesicle-mediated transport, taking part in the initial vesicle formation, transport of vesicles along the cytoskeleton, and eventual fusion of vesicle and target membranes. Rab4 is localized at early endosomes/recycling endosomes and functions as a key regulator for sorting/recycling of membrane and proteins (1,2). Both Rab4A and Rab4B isoforms are localized to similar cellular compartments and are believed to have similar functions (4). Rab4 interacts with several Rab4 effectors in a complex on a special endosome site to promote membrane/protein recycling (1,3). Rab5 is localized to the plasma membrane and early endosome and functions as a key regulator of vesicle trafficking during early endocytosis (1). The conformational change between Rab5-GTP and Rab5-GDP is essential for its biological function as a rate-limiting regulator at multiple steps during endocytosis (1,5). Similar to Rab4, Rab5 also interacts with specific Rab5 effectors on a specialized endosomal Rab domain to promote recycling between endosome and the plasma membrane (1,5,6). Both Rab7 and Rab9 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 (7,8). Rab7 also helps to regulate growth receptor endocytic trafficking and degradation, and maturation of phagosome and autophagic vacuoles (8-11). Rab9 interacts with its effector proteins p40 and TIP47 (12,13) to promote the MPR (mannose 6-phosphate receptor)-associated lysosomal enzyme transport between late endosomes and the trans Golgi network (14,15). Rab11 (isoforms Rab11a and Rab11b) functions as a key regulator in the recycling of perinuclear, plasma membrane and Golgi compartment endosomes (16,17). Despite some overlap, distinct differences exist between Rab11a and Rab11b in both their cellular distribution and functional roles. Rab11a is ubiquitously expressed while Rab11b is found mainly in the heart and brain (18,19). Like other Rab proteins, Rab11 functions when associated with Rab11 family interacting proteins (FIPs). The three distinct classes of Rab11 FIPs all share a conserved carboxy-terminal Rab-binding domain that allows Rab-FIP protein interaction. When bound together, these proteins are thought to regulate membrane-associated protein sorting (20,21).