The Function Of Rab Protein In Natural Immunity And Tumor

The dynamic trafficking of intracellμlar membrane is crucial to the life of the cell, which regμlate the basic life processes, including signal transduction, energy transduction, and material transport. A plurality of protein family are involved in the vesicle traffick, beside soluble N-ethylmaleimide-sensitive factor activating protein receptors(SNAREs), Coats, Tethers and motor proteins, the Rab GTPases serve as mμltifaceted organizers of almost all vesicle trafficking processesIn the diverse array of proteins involved in these procedures, Rab proteins emerge to serve as master regμlators for systemic integration. Rabs are the largest and most diverse family of small GTPases, which clustered together in a monophyletic branch of Ras superfamily. In mammal, there are more than 70 Rab proteins, which specifically localized at particμlar subcellμlar vesicle compartment upon activation. The activity of Rabs are tightly controlled by its binding with GTP and GTP to GDP hydrolysis, which produce different conformation(GTP-bound active conformation versus GDP-bound inactive conformation) to be decoded by various interacting proteins. There are three large classes of Rab interacting proteins that switch the activation status of Rab protein: guanine-exchange factors(GEF), GTPase activating proteins(GAPs) and GDP-dissociation inhibitors(GDIs). Another class of Rab-interacting partners are composed with various effector proteins that function in specific Rab-assembled complexes to implement distinct downstream functions.As an information exchange center coordinating immune response, innate dendritic cells(DCs) orchestrated complex membrane trafficking events to parse the invading pathogens and transformed tumor cells to adaptive immunological system. From engulfment to degradation to major histocompatibility complex(MHC) loading, the antigen presentation was compartmentalized into different vacuoles and integrated into a consecutive process by endocytic membrane transportation; meanwhile, recognition of pathogen-associated or danger-associated molecular pattern(PAMP or DAMP) by DCs triggers the organized inflammatory signaling cascade on the surface of various intracellular vesicles, which polarizes the adaptive responses through cytokine/chemokine secretion. For example, Rab27 a is required to limit the acidification phagosomes and promote cross presentation; Salmonella enterica prevent antigen presentation in DC by type III secretion of Sif A, a protein that antagonize Rab9 function and therefore inhibits lysosomal degradation Therefore, depicting networks and mechanisms of membrane trafficking will greatly facilitate the nature of innate defense in dendritic cells.In this study, we developed a novel tandem affinity purification procedure and 51 dendritic cell lines stably expressing individual tagged-Rab GTPases. Aided by liquid chromatography-electrospray ionization-tandem mass spectrometry(LC-ESI-MS/MS), a comprehensive proteomics study was performed to pursuit interacting proteins for each Rab family member. 8874 bait-prey pairs and 1670 unique prey proteins were identified; and, within this data set, 649 pairs and 373 unique preys were designate to be high confidence partners by Comp PASS. This comprehensive proteomics analysis provided a global view of intracellular membrane organization and when complemented by various imaging tools, inspired many novel hypotheses on the functions of Rab subnetworks in dendritic cells. Specifically, we investigated dynamic changes to the Rab32 subnetwork in DCs induced by L. monocytogenes infection, and uncovered a novel and essential role of this subnetwork in controlling the intracellular proliferation of Listeria in vitro and in vivo. Mechanistically, Rab32 formed a persistent complex with two newly identified interacting proteins-Phb and Phb2-to envelope bacteria both during early phagosome formation and after Listeria escapes the original containment vacuole. In addition, all three proteins are indispensable for the process of phagosome to lysosome transition. Collectively, the establishment of a functional compartmentalization overview and an organizational framework of intracellular Rab-mediated vesicle trafficking ? exemplified by the discovery of the anti-microbial Rab32-Phb-Phb2 complex ? underscore the importance of this work as a resource for future investigations.In recent years, imbalances in Rab-mediated vesicle trafficking processes are known to have an important role in tumor development, including cell proliferation, migration, invasion of the extracellular matrix, and drug resistance. We performed a global analysis of the m RNA expression level of Rab GTPases in gastric cancer(GC) patients, and found that Rab40 b was associated with GC clinicopathological factors. In addition, our experimental results demonstrate that Rab40 b affect GC cells migration, invasion, and metastasis. These findings indicate that Rab40 b might be a novel candidate molecule involved in GC development, thus identifying a potential biological therapeutic target for GC.