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A wealth of in vitro data has demonstrated a central role for receptor ubiquitination in endocytic sorting. However, how receptor ubiquitination functions in vivo is poorly understood. Herein, we report that ablation of B cell antigen receptor ubiquitination in vivo uncouples the receptor from CD19 phosphorylation and phosphatidylinositol 3-kinase (PI3K) signals. These signals are necessary and sufficient for accumulating phosphatidylinositol (3,4,5)-trisphosphate (PIP3) on B cell receptor-containing early endosomes and proper sorting into the MHC class II antigen-presenting compartment (MIIC). Surprisingly, MIIC targeting is dispensable for T cell-dependent immunity. Rather, it is critical for activating endosomal toll-like receptors and antiviral humoral immunity. These findings demonstrate a novel mechanism of receptor endosomal signaling required for specific peripheral immune responses.

Original publication




Journal article


J Exp Med

Publication Date





3775 - 3790


Animals, B-Lymphocytes, CD79 Antigens, Endocytosis, Endosomes, Histocompatibility Antigens Class II, Immunity, Humoral, Male, Mice, Inbred C57BL, Phosphatidylinositol 3-Kinase, Phosphatidylinositol Phosphates, Receptors, Antigen, B-Cell, Signal Transduction, Toll-Like Receptors, Ubiquitin, Ubiquitination