RAB11B

Members of the Rab11 subfamily act in recycling of proteins from the endosomes to the plasma membrane, in transport of molecules from the trans-Golgi network to the plasma membrane and in phagocytosis. This subfamily also acts in polarized transport in epithelial cells. Whereas most studies refer to the Rab11a isoform, little is known about Rab11b so far. Rab11b localizes predominantly in the pericentriolar recycling compartment and serves as an important component of the vesicular machinery. It is required for the transfer of internalized transferrin from the recycling compartment to the plasma membrane for which active Rab11b as well as GTP hydrolysis is necessary. == Structure ==

All Ras GTPases consist of a similar core structure and highly conserved P-loop, switch 1 and switch 2 regions. The Rab11b monomer exhibits a typical Ras-like, small GTPase fold with a six stranded β-sheet core (β1-β6) surrounded by five major α-helices (α1-α5) The major divergence reveals in the inactive state. While Pasqualato et al. crystallized inactive Rab11a as a dimer in the asymmetric unit, Scapin et al. observed single crystallographically independent monomers of both the GDP- and the GppNHp-bound Rab11b structures. == Clinical significance ==

Due to their crucial importance in vesicle transport and recycling, Rab11 proteins are linked to various non-pathogen or pathogen induced diseases. Most of the published data do not specify whether it is the a- or the b-isoform. Rab11 proteins have been implicated in Alzheimer's disease, Arthrogryposis-renal dysfunction-cholestasis (ARC), Batten disease, and Charcot-Marie-Tooth Neuropathy Type 4C (CMT4C). Intracellular bacteria Chlamydia pneumoniae and Chlamydia trachomatis that replicate in membrane bound compartments hijack the trafficking machinery recruiting Rab GTPases to promote their replication within the host cell. Knock down of Rab11 decreased the formation of infectious particles. Recent studies report a similar use of intracellular trafficking by Hantavirus and Influenza A virus. Replicated viruses benefit from Rab11 mediated recycling endosome pathway to exit the cell and infect surrounding tissue. == References ==