Proteome dynamics reveal temporal regulation of O-GlcNAcylation/phosphorylation in determining apoptosis of activated B cells

摘要

Here, we decipher the molecular mechanisms bridging B cell activation and apoptosis mediated by post-translational modification (PTM). We found that O-GlcNAcase inhibition enhances B cell activation and apoptosis induced by B cell receptor (BCR) cross-linking. This proteome-scale analysis of the functional interplay between protein O-GlcNAcylation and phosphorylation in stimulated mouse primary B cells identified 313 O-GlcNAcylation-dependent phosphosites on 224 phosphoproteins. Among these phosphoproteins, temporal regulation of the O-GlcNAcylation and phosphorylation of lymphocyte-specific protein-1 (Lsp1) is a key switch that triggers apoptosis in activated B cells. O-GlcNAcylation at S209 of Lsp1, identified as the major O-GlcNAc site on Lsp1 by both electron-transfer dissociation and collision-induced dissociation tandem mass spectrometry, was a prerequisite for the recruitment of its kinase, PKC-β1, to induce S243 phosphorylation, leading to ERK activation and down-regulation of BCL-2 and BCL-xL. Thus, we demonstrate the critical PTM interplay of Lsp1 that transmits signals for initiating apoptosis after BCR ligation.