ROLE OF SNX17 IN THE REGULATION OF ACTIN CYTOSKELETON AND PHAGOSOMAL MATURATION BY DENDRITIC CELLS

DINAMARCA, SOFÍA; SALVIONI, ANNA; CEBRIÁN, IGNACIO; CROCE, CRISTINA; BLANCHARD, NICOLAS; GARRIDO, FACUNDO; MAYORGA, LUIS

Buenos Aires

Congreso; LVI SAIB and XV SEMIGE Meeting; 2020

SAIB-SEMIGE

Dendritic cells (DCs) have deeply adapted their endocytic network, achieving a cross-presentation efficiency higher than any other antigen-presenting cell. This implies the proper internalization, processing and presentation of exogenous antigens derived from different pathogens or tumor cells in the context of MHC-I molecules to trigger cytotoxic T cell responses. On the other hand, sorting nexins (SNXs) are proteins characterized by the presence of a PX domain that interacts with PI3P, therefore they are mostly distributed within early endosomal compartments. From there, SNXs control very important intracellular events, such as endocytosis, signaling, sorting, and endosomal tubulation. In the context of DCs, we have shown that SNX17 represents an important regulator of the cross-presentation of soluble, particulate and Toxoplasma gondii-associated antigens. Furthermore, we have demonstrated that SNX17 plays a pivotal role to guarantee the efficient internalization of exogenous antigens and the recycling of integrins by DCs. In this study, we decided to delve into the role of SNX17 during phagosomal maturation and the actin cytoskeleton?s organization. By silencing the expression of SNX17 in DCs (SNX17 KD), we determined by flow cytometry that the phagosomes isolated from these cells are unable to correctly degrade the antigen and acquire the lysosomal marker Lamp1. Moreover, due to the morphological changes exhibited by SNX17 KD DCs, as compared to control DCs (Scramble), and the impairment to achieve normal antigen internalization, we examined the organization of the actin cytoskeleton. By combining confocal microscopy and flow cytometry techniques, we observed that SNX17 KD DCs lose the normal distribution of actin in the dendrites at the cell surface. We also show that this is consequence of a defect in actin organization rather than an impossibility to polymerize actin. Altogether, our findings highlight the role of SNX17 as a key regulator of cross-presentation through the control of antigen internalization and phagosomal maturation.