Figure 1 of Lin, Mol Vis 2009; 15:26-37.


Figure 1. Effect of norrin on tPA and uPA expression, and on survival of RGC-5 cells. In the absence (A,B,E) or presence of 2.0 μM staurosporine (SS; C,D,F), RGC-5 cells were left untreated or treated for 48 h with varying concentrations of norrin (n=3 experiments). At the end of 48 h, conditioned medium was collected and proteolytic activity of tissue plasminogen activator (tPA) and and urokinase plasminogen activator (uPA) was determined by zymography assays (A,C), relative amount of proteolytic activity was determined by densitometric analysis (B,D), and cell viability was assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assays (E, F). In the absence of SS, norrin had no effect on low levels of uPA expressed constitutively by RGC-5 cells (A,B; NS is not significant). In addition, lower concentrations of norrin had no effect on cell survival, but higher concentrations of norrin (50 and 100 ng/ml) increased cell survival significantly (E, *p<0.05). Compared to low levels of uPA expressed by untreated cells, uPA (D, #p<0.05) and tPA (D, **p<0.05) levels were significantly increased in SS alone or in SS and norrin-treated cells. Nonetheless, survival of RGC-5 cells decreased significantly in the presence of SS alone (F, *p<0.05), but not in the presence of SS and norrin (F, **p<0.05).