Tumor necrosis factor-alpha regulates the Hypocretin system via mRNA degradation and ubiquitination

• Published in: Biochimica et biophysica acta 2011-04, Vol.1812 (4), p.565-571
• Main Authors: Zhan, Shuqin, Cai, Guo-Qiang, Zheng, Anni, Wang, Yuping, Jia, Jianping, Fang, Haotian, Yang, Youfeng, Hu, Meng, Ding, Qiang
• Format: Article
• Language: English
• Subjects: Animals; Cell Line, Tumor; Down-Regulation; Hypocretin; Hypocretin receptor; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - metabolism; Neuropeptides - genetics; Neuropeptides - metabolism; Orexin; Orexin receptor; Orexin Receptors; Orexins; Rats; Receptors, G-Protein-Coupled - genetics; Receptors, G-Protein-Coupled - metabolism; Receptors, Neuropeptide - genetics; Receptors, Neuropeptide - metabolism; RNA Stability; RNA, Messenger - genetics; Sleep disorder; Sleep Wake Disorders - etiology; Tumor necrosis factor; Tumor Necrosis Factor-alpha - metabolism; Ubiquitination
• ISSN: 0925-4439; 0006-3002; 1879-260X
• DOI: 10.1016/j.bbadis.2010.11.003

Recent studies recognize that Hypocretin system (also known as Orexin) plays a critical role in sleep/wake disorders and feeding behaviors. However, little is known about the regulation of the Hypocretin system. It is also known that tumor necrosis factor alpha (TNF-α) is involved in the regulation of sleep/wake cycle. Here, we test our hypothesis that the Hypocretin system is regulated by TNF-α. Prepro-Hypocretin and Hypocretin receptor 2 (HcrtR2) can be detected at a very low level in rat B35 neuroblastoma cells. In response to TNF-α, Prepro-Hypocretin mRNA and protein levels are down-regulated, and also HcrtR2 protein level is down-regulated in B35 cells. To investigate the mechanism, exogenous rat Prepro-Hypocretin and rat HcrtR2 were overexpressed in B35 cells. In response to TNF-α, protein and mRNA of Prepro-Hypocretin are significantly decreased (by 93% and 94%, respectively), and the half-life of Prepro-Hypocretin mRNA is decreased in a time- and dose-dependent manner. The level of HcrtR2 mRNA level is not affected by TNF-α treatment; however, HcrtR2 protein level is significantly decreased (by 86%) through ubiquitination in B35 cells treated with TNF-α. Downregulation of cellular inhibitor of apoptosis protein-1 and -2 (cIAP-1 and -2) abrogates the HcrtR2 ubiquitination induced by TNF-α. The control green fluorescent protein (GFP) expression is not affected by TNF-α treatment. These studies demonstrate that TNF-α can impair the function of the Hypocretin system by reducing the levels of both Prepro-Hypocretin and HcrtR2. ▶ The pro-inflammation cytokine, TNF-alpha, impairs the Hypocretin/Orexin system. ▶ TNF-alpha decreases the expression of Prepro-Hypocretin and Hypocretin receptor 2. ▶ TNF-alpha increases mRNA degradation and ubiquitination of the Hypocretin system. ▶ Impaired Hypocretin system contributes to the development of sleep disorders. ▶ TNF-alpha may regulate the sleep-wake cycle through the Hypocretin system.