title: Tumor necrosis factor-alpha regulates the Hypocretin system via mRNA degradation and ubiquitination.
abstract: 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.
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA. shqzhan@hotmail.com
authors.forename: Shuqin
authors.initials: S
authors.lastname: Zhan
authors.forename: Guo-Qiang
authors.initials: GQ
authors.lastname: Cai
authors.forename: Anni
authors.initials: A
authors.lastname: Zheng
authors.forename: Yuping
authors.initials: Y
authors.lastname: Wang
authors.forename: Jianping
authors.initials: J
authors.lastname: Jia
authors.forename: Haotian
authors.initials: H
authors.lastname: Fang
authors.forename: Youfeng
authors.initials: Y
authors.lastname: Yang
authors.forename: Meng
authors.initials: M
authors.lastname: Hu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ding
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D015536:Down-Regulation; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism*; D064446:Orexin Receptors; D000068797:Orexins; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D018013:Receptors, Neuropeptide / Q000235:genetics / Q000378:metabolism*; D012893:Sleep Wake Disorders / Q000209:etiology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: C578625:Hcrtr2 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide; D014409:Tumor Necrosis Factor-alpha