The deubiquitinating enzyme USP48 stabilizes TRAF2 and reduces E-cadherin-mediated adherens junctions

• Published in: The FASEB journal Vol. 32; no. 1; p. 230
• Main Authors: Li, Shuang, Wang, Dan, Zhao, Jing, Weathington, Nathaniel M, Shang, Dong, Zhao, Yutong
• Format: Journal Article
• Language: English
• Published: United States 01.01.2018
• Subjects: A549 Cells; Adherens Junctions - metabolism; Animals; Antigens, CD; Cadherins - metabolism; Cell Line; Epithelial Cells - metabolism; Gene Knockdown Techniques; Glycogen Synthase Kinase 3 beta - metabolism; HEK293 Cells; Humans; MAP Kinase Signaling System; Mice; Phosphorylation; Protein Stability; TNF Receptor-Associated Factor 2 - chemistry; TNF Receptor-Associated Factor 2 - metabolism; Tumor Necrosis Factor-alpha - metabolism; Ubiquitin-Specific Proteases - antagonists & inhibitors; Ubiquitin-Specific Proteases - genetics; Ubiquitin-Specific Proteases - metabolism; Ubiquitination; epithelial barrier integrity; deubiquitination; signal pathway; phosphorylation
• ISSN: 1530-6860
• DOI: 10.1096/fj.201700415RR

The tumor necrosis factor receptor-associated factor 2 (TRAF2) is a second messenger adaptor protein that plays an essential role in propagating TNF-α-mediated signaling pathways. Modulation of TRAF2 activity by ubiquitination is well studied; however, the deubiquitinating enzyme (DUB), which regulates TRAF2 stability, has not been identified. Here we reveal USP48 as the first identified DUB to deubiquitinate and stabilize TRAF2 in epithelial cells. Down-regulation of USP48 increases K48-linked polyubiquitination of TRAF2 and reduces TRAF2 protein levels. Interestingly, USP48 only targets the TRAF2 related to JNK pathway, not the TRAF2 related to NF-κB and p38 pathways. USP48 is serine phosphorylated in response to TNF-α. The phosphorylation is catalyzed by glycogen synthase kinase 3β (GSK3β), ultimately resulting in increases in USP48 DUB activity. Furthermore, we reveal a new biologic function of TRAF2 that contributes to epithelial barrier dysfunction, which is attenuated by knockdown of USP48. Inhibition of TRAF2/JNK pathway increases E (epithelial)-cadherin expression and enhances epithelial barrier integrity, while knockdown of USP48 attenuates TNF-α/JNK pathway and increases E-cadherin expression and cell-cell junction in epithelial cells. These data, taken together, indicate that USP48 stabilizes TRAF2, which is promoted by GSK3β-mediated phosphorylation. Further, down-regulation of USP48 increases E-cadherin expression and epithelial barrier integrity through reducing TRAF2 stability.-Li, S., Wang, D., Zhao, J., Weathington, N. M., Shang, D., Zhao, Y. The deubiquitinating enzyme USP48 stabilizes TRAF2 and reduces E-cadherin-mediated adherens junctions.