Figure 3:

USP18 null mice are markedly sensitive to cold stress and this is associated with reduced UCP1 protein expression. (A) USP18 null mice had impaired ability to maintain their basal temperature after exposure to cold stress. Protein levels were quantified relative to tubulin expression and normalized to examined wild-type murine tissues. (B) UCP1 expression is displayed in brown adipose fat of USP18 null mice versus the murine KHC1 USP18−/− null leiyomyosarcoma cell line. Protein levels were quantified relative to tubulin expression. Protein expression profiles were normalized to empty vector-transfected KHC1 cells. (C) Gain of USP18 expression independently achieved in human and murine lung cancer cell lines conferred enhanced expression of UCP1 protein. (D) Gain of USP18 expression in 293T cells substantially decreased total ubiquitination and UBE1 levels. Protein levels were quantified relative to actin expression and normalized to examined empty-vector transfected cells, as displayed in this panel. The quantification of immunoblots shows the average of three independent experiments. Representative immunoblots are displayed. The symbols refer to * P < 0.05 and ** P < 0.01, respectively.