Role of the GTPase Rab22a in the recruitment of ER components to dendritic cell phagosomes and endosomes

CROCE, CRISTINA; MAYORGA, LUIS S.; DINAMARCA, SOFÍA; ZALAZAR, ALEJANDRO; CEBRIAN, IGNACIO

Buenos Aires

Congreso; Reunión conjunta de Sociedades de Biociencias; 2017

SAIC-SAIB-SAI-SAA-SAB-SAB-SAFE-SAFIS-SAH-SAP

Cross-presentation is the process by which antigen presenting cells (APCs) expose exogenous antigens-derived peptides in association with MHC class I molecules to CD8+ T lymphocytes in order to trigger cytotoxic immune responses. In this context, dendritic cells (DCs) are the most potent APC able to achieve cross-presentation efficiently. Several studies have focused on deciphering the molecular mechanisms underlying this process, but the connection between the endocytic network and endoplasmic reticulum (ER)-derived compartments is still poorly understood. In this study, we have investigated the role of the small GTPase Rab22a during the delivery of ER resident proteins to DC endosomes and phagosomes. In a previous work, we have shown that Rab22a is crucial to regulate antigen cross-presentation, the phagosomal acquisition of MHC-I and the recycling of these molecules to the cell surface in DCs. Now, we show that the knock-down (KD) of Rab22a expression in DCs impairs the normal delivery of ER components exclusively to endosomes but not to phagosomes, suggesting a differential role of Rab22a in these compartments. We have validated these observations by performing a biochemistry assay (phagosomal purification), immunofluorescence and confocal microscopy, and a flow cytometry-based approach. Furthermore, we evidenced that endosomal maturation is drastically altered in Rab22a KD DCs, as compared to control cells. Interestingly, this phenomenon was not observed during the process of phagosomal maturation. Altogether, our results indicate that Rab22a displays major regulatory functions in endosome maturation and is important to guarantee the proper recruitment of ER components to DC endosomes.