Lys48-linked TAK1 polyubiquitination at lysine-72 downregulates TNFα-induced NF-κB activation via mediating TAK1 degradation

摘要

Protein kinases are important regulators of intracellular signal transduction pathways and play critical roles in diverse cellular processes. TAK1, a member of the MAPKKK family, is essential for TNFα-induced NF-κB activation. Phosphorylation and Lys⁶³-linked polyubiquitination (polyUb) of TAK1 are critical for its activation. However, whether TAK1 is regulated by polyubiquitination-mediated protein degradation after its activation remains unknown. Here we report that TNFα induces TAK1 Lys⁴⁸ linked polyubiquitination and degradation at the later time course. Furthermore, we provide direct evidence that TAK1 is modified by Lys⁴⁸-linked polyubiquitination at lysine-72 by mass spectrometry. A K72R point mutation on TAK1 abolishes TAK1 Lys⁴⁸-linked polyubiquitination and enhances TAK1/TAB1 co-overexpression-induced NF-κB activation. As expected, TAK1 K72R mutation inhibits TNFα-induced Lys⁴⁸-linked TAK1 polyubiquitination and degradation. TAK1 K72R mutant prolongs TNFα-induced NF-κB activation and enhances TNFα-induced IL-6 gene expression. Our findings demonstrate that TNFα induces Lys⁴⁸-linked polyubiquitination of TAK1 at lysine-72 and this polyubiquitination-mediated TAK1 degradation plays a critical role in the downregulation of TNFα-induced NF-κB activation.