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Deubiquitinating enzymes (DUBs) regulate diverse cellular functions by their activity of cleaving ubiquitin from specific protein substrates. Ubiquitin-Specific Protease 46 (USP46) has recently been identified as a quantitative trait gene responsible for immobility in the tail suspension test and forced swimming test in mice. Mice with a lysine codon (Lys 92) deletion in USP46 exhibited loss of ‘behavioral despair’ under inescapable stresses in addition to abnormalities in circadian behavioral rhythms and the GABAergic system. However, whether this deletion affects enzyme activity is unknown. Here we show that USP46 has deubiquitinating enzyme activity detected by USP cleavage assay using GST-Ub52 as a model substrate. Interestingly, compared to wild type, the Lys 92 deletion mutant resulted in a decreased deubiquitinating enzyme activity of 27.04%. We also determined the relative expression levels of Usp46 in rat tissues using real-time RT-PCR. Usp46 mRNA was expressed in various tissues examined including brain, with the highest expression in spleen. In addition, like rat USP46, both human and mouse USP46 are active toward to the model substrate, indicating the USP cleavage assay is a simple method for testing the deubiquitinating enzyme activity of USP46. These results suggest that the Lys 92 deletion of USP46 could influence enzyme activity and thereby provide a molecular clue how the enzyme regulating the pathogenesis of mental illnesses.

Smoking is considered to be one of the primary causes of atherosclerosis and vascular injury. Previous studies have shown that nicotine in tobacco can lead to vascular inflammation and endothelial dysfunction. Perivascular adipose tissue (PVAT) is known to secrete various types of adipokines to maintain vascular homeostasis. The present study investigated whether nicotine‑induced PVAT malfunction can accelerate endothelial inflammation and eventually lead to endothelial dysfunction. The levels of inflammatory adipokines, including nuclear factor (NF)‑κB, interleukin (IL)‑1β, IL‑6 and tumor necrosis factor (TNF)‑α, the ICAM‑1 and VCAM‑1 adhesion molecules and secretion of adiponectin were assessed in mature adipocytes and endothelial cells cultured alone or in co‑culture under nicotine stimulation. It was found that nicotine reduced the secretion of adiponectin and stimulated secretion of the NF‑κB, IL‑1β, IL‑6 and TNF‑α inflammatory adipokines in mature adipocytes. Although nicotine stimulated endothelial cells to secrete IL‑1β and IL‑6, no significant increase in the secretion of TNF‑α was observed. The co‑culture of mature adipocytes with endothelial cells markedly augmented the expression of the NF‑κB, IL‑1β, IL‑6 and TNF‑α inflammatory adipokines and the ICAM‑1 and VCAM‑1 adhesion molecules, and significantly lowered the levels of adiponectin. These findings suggested that nicotine induced mature adipocyte dysfunction, which caused the abnormal secretion of adiponectin and inflammatory adipokines, and exacerbated endothelial inflammation. These findings also suggested a mechanism whereby nicotine induced the secretion of adiponectin and inflammatory cytokines by adipocytes. The results of the present study elucidated a novel pathway induced by cigarette smoke, which contributed to atherosclerosis and vascular injury.