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Rab7b and receptors trafficking
No full textRab proteins are key-regulators of intracellular membrane trafficking. Rab7b is a recently identified Rab protein that may downregulate TLR4 and TLR9-mediated inflammatory responses. Rab7b, believed to have similar function as Rab7, controls however vesicular trafficking from endosomes to the TGN. It is localized to late endosomes/lysosomes as well as the TGN. Rab7b interferes with enzymes delivery to lysosomes and with the retrograde Shiga toxin transport to the Golgi. Furthermore, Rab7b depletion alters CI-MPR and TGN46 trafficking. In conclusion, Rab7b, by regulating the transport from late endosomes to the TGN, is fundamental for trafficking of several receptors, opening for a revised scenario for its influence on signaling of Toll-like Receptors (TLRs) and other receptors
RILP interacts with the VPS22 component of the ESCRT-II complex
No full textThe Rab-interacting lysosomal protein (RILP) has been identified as an effector for the small GTPases Rab7 and Rab34. It has been demonstrated that Rab7 and RILP are key proteins for the biogenesis of lysosomes and phagolysosomes. Indeed, expression of dominant negative mutants of Rab7 or of the C-terminal half of RILP impairs biogenesis and function of these organelles. In this study we have isolated, using the yeast two-hybrid system, the EAP30/SNF8/VPS22 subunit of the ESCRT-II complex as a RILP interacting protein. We demonstrated that VPS22 interacts with the N-terminal half of RILP. The interaction data obtained with the two-hybrid system were confirmed by co-immunoprecipitation. In addition, confocal immunofluorescence revealed colocalization of GFP-RILP and HA-VPS22. These data suggest that RILP could have a role in the biogenesis of multivesicular bodies
Vimentin phosphorylation and assembly are regulated by the small GTPase Rab7a
Full text linkIntermediate filaments are cytoskeletal elements important for cell architecture. Recently it has been discovered that intermediate filaments are highly dynamic and that they are fundamental for organelle positioning, transport and function thus being an important regulatory component of membrane traffic. We have identified, using the yeast two-hybrid system, vimentin, a class III intermediate filament protein, as a Rab7a interacting protein. Rab7a is a member of the Rab family of small GTPases and it controls vesicular membrane traffic to late endosomes and lysosomes. In addition, Rab7a is important for maturation of phagosomes and autophagic vacuoles. We confirmed the interaction in HeLa cells by co-immunoprecipitation and pull-down experiments, and established that the interaction is direct using bacterially expressed recombinant proteins. Immunofluorescence analysis on HeLa cells indicate that Rab7a-positive vesicles sometimes overlap with vimentin filaments. Overexpression of Rab7a causes an increase in vimentin phosphorylation at different sites and causes redistribution of vimentin in the soluble fraction. Consistently, Rab7a silencing causes an increase of vimentin present in the insoluble fraction (assembled). Also, expression of Charcot-Marie-Tooth 2B-causing Rab7a mutant proteins induces vimentin phosphorylation and increases the amount of vimentin in the soluble fraction. Thus, modulation of expression levels of Rab7a wt or expression of Rab7a mutant proteins changes the assembly of vimentin and its phosphorylation state indicating that Rab7a is important for the regulation of vimentin function
Meningococcal Hrpa/HrpB two partner secretion (TPS) system is essential for intracellular survival
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