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-?) is involved in the regulation of sleep/wake cycle. Here, we test our hypothesis that the Hypocretin system is regulated by TNF-?. Prepro-Hypocretin and Hypocretin receptor 2 (HcrtR2) can be detected at a very low level in rat B35 neuroblastoma cells. In response to TNF-?, 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-?, 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-? treatment; however, HcrtR2 protein level is significantly decreased (by 86%) through ubiquitination in B35 cells treated with TNF-?. Downregulation of cellular inhibitor of apoptosis protein-1 and -2 (cIAP-1 and -2) abrogates the HcrtR2 ubiquitination induced by TNF-?. The control green fluorescent protein (GFP) expression is not affected by TNF-? treatment. These studies demonstrate that TNF-? can impair the function of the Hypocretin system by reducing the levels of both Prepro-Hypocretin and HcrtR2.

SUBMITTER: Zhan S 

PROVIDER: S-EPMC3042489 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature