Fc immunoreceptors promote autophagy to regulate monocyte functions

Receptors for the Fc fragment of immunoglobulin G (FcyRs) are critical in the defense against pathogens and in monoclonal antibody-based therapies. When activated by immune complexes or opsonized particles, FcyRs are endocytosed. Components of the endocytosis machinery are used during autophagy, a process which is triggered by starvation or by activation of specific receptors. In this work, we demonstrate that activation of FcyRs initiates autophagy, characterized by formation of p62 protein puncta and activation of ULK1, a major component of the autophagy initiation complex. Autophagy induction downstream of FcyRs activation involves the protein phosphatase Pp2a and its enzymatic activity, as demonstrated by in situ protein labeling. In animal models in which autophagy was inactivated or enhanced in myeloid cells, autophagy negatively regulates pro-inflammatory cytokine production downstream of FcyRs receptors, while being required for FcyRs -mediated antibody-induced cell phagocytosis and myeloid cell survival. Our results suggest that, for antibody-based therapeutic strategies that target the activation of FcyRs, an additional level of control can be obtained by manipulation of autophagy.