Dendritic cell phagosomes recruit GRASP55 for optimal transport of antigen-loaded MHC molecules to the plasma membrane

IGNACIO CEBRIÁN; SOFÍA DINAMARCA; MARÍA JESÚS PENA RODRÍGUEZ; PRIEGO, ELENA; NATHALIE BROUWERS; MARTINA BARENDS; JAMINA BRUNNBERG; ROBERT TAMPÉ; NICOLAS BLANCHARD; DAVID SANCHO; VIVEK MALHOTRA

Buenos Aires

Congreso; 14th Latin American and Caribbean Congress of Immunology; 2024

SAI - ALACI - AINCA

Background: Dendritic cells (DCs) are highly adapted to present exogenous antigen-derived peptides in association with MHC class I and II molecules, which triggers activation of CD8+ and CD4+ T lymphocytes, respectively. The former process is called cross-presentation, while the latter is the classical MHC-II presentation pathway. The endocytic network is essential for antigen processing to generate peptides that are loaded onto MHC molecules. However, the final steps in the traffic of MHC/peptide complexes from the endocytic system to cell surface remain poorly understood. Objective: The main objective of this study was to explore the role of the Golgi reassembly-stacking protein of 55 kDa (GRASP55) during the phagosomal export of antigen-loaded MHC molecules. This research’s rationale is that GRASP55 regulates unconventional protein secretion, and this pathway shares similarities with the exogenous antigen presentation pathways. Methods: We performed different flow cytometry-based experiments, antigen presentation assays, confocal microscopy analysis, and biochemistry techniques to address this study in wild type (WT) and GRASP55-/- bone marrow-derived DCs (BMDCs). Results: We show that GRASP55 plays an essential role in antigen presentation. Using a model antigen coated to latex beads, soluble or associated to Escherichia coli, we found that both MHC-I cross-presentation and MHC-II antigen presentation are significantly inhibited in BMDCs of GRASP55-/- C57BL/6 mice compared to WT DCs. GRASP55 was recruited to late DC phagosomes and necessary for efficient sorting of loaded MHC-I and -II molecules from phagosomes to the plasma membrane. Conclusion: Our data show that GRASP55 is crucial for the intracellular transport of MHC-I and -II molecules in the process of exogenous antigen presentation.