Temporal regulation of Lsp1 O-GlcNAcylation and phosphorylation during apoptosis of activated B cells
醣啟動了調控活化B細胞存亡之樞紐

Nat Commun. 2016, 7, 12526.
Wu JL, Wu HY, Tsai DY, Chiang MF, Chen YJ, Gao S, Lin CC, Lin CH, Khoo KH, Chen YJ, Lin KI

Crosslinking of B-cell receptor (BCR) sets off an apoptosis programme, but the underlying pathways remain obscure. Here we decipher the molecular mechanisms bridging B-cell activation and apoptosis mediated by post-translational modification (PTM). We find that O-GlcNAcase inhibition enhances B-cell activation and apoptosis induced by BCR crosslinking. This proteome-scale analysis of the functional interplay between protein O-GlcNAcylation and phosphorylation in stimulated mouse primary B cells identifies 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 is a prerequisite for the recruitment of its kinase, PKC-β1, to induce S243 phosphorylation, leading to ERK activation and downregulation of BCL-2 and BCL-xL. Thus, we demonstrate the critical PTM interplay of Lsp1 that transmits signals for initiating apoptosis after BCR ligation.

Temporal regulation of Lsp1 O-GlcNAcylation and phosphorylation during apoptosis of activated B cells

O連結乙醯葡萄氨糖修飾是細胞中的一種後轉錄調控修飾作用,在細胞中此種修飾是經由OGT酵素在蛋白質的絲氨酸和蘇氨酸進行催化完成,另一個酵素OGA則負責將此修飾移除。由於此種修飾是發生在絲氨酸和蘇氨酸上,其在細胞中所參與的許多作用被認為是藉由影響磷酸化修飾來達成。磷酸化蛋白質體和O 連結乙醯葡萄氨糖修飾之同時分析,我們發現高達313個磷酸化點位受到乙醯葡萄氨糖之影響, 其中,Lsp1 蛋白會被 O 連結乙醯葡萄氨糖修飾在絲氨酸 209 位點上。並進而啟動絲氨酸 243 位點的磷酸化透過 Lsp1 蛋白不同的後轉譯修飾突變進行功能性分析時,我們觀察到 Lsp1 蛋白的 O 連結乙醯葡萄氨糖修飾和絲氨酸 243 位點的磷酸化會調控B 細胞的細胞凋亡作用之重要機制,實驗結果發現Lsp1 蛋白的 O 連結乙醯葡萄氨糖修飾是藉由增加 Lsp1 蛋白和負責絲氨酸 243 位點的磷酸化之激酶,PKC-β1 的接合量來達成促進下游和細胞凋亡相關的訊息傳遞體之活化,及降低BCL-2 和 BCL-xL 的表現來達成促進細胞凋亡的作用。綜合上述,我們的實驗結果闡述了蛋白 O 連結乙醯葡萄氨糖修飾和磷酸化修飾之間的動態交互作用決定了 B 細胞受受體接合而活化後的細胞凋亡命運。