Fig. 6

The role of PTP1B in Src-dependent microglial activation. a PTP1B overexpression dephosphorylated Src at Y527, a negative regulatory site. The phosphorylation of Src Y527 was quantified and normalized to total Src in either control or HA-PTP1B-transfected BV-2 cells. The graph shows the average value of phosphorylation of Y527/β-actin from four independent experiments. *p < 0.05 control versus HA-PTP1B-transfected BV-2, Student t test. b The phosphorylation of Src Y416 and p38 was quantified and normalized to total Src levels following treatment of BV-2 cells with LPS (100 ng/ml) or PTP1Bi (10 μM) for 30 min. The graph shows the average value of phosphorylation of Y416/total Src expression from four independent experiments. *p < 0.05 versus LPS only; analyzed by one-way ANOVA with Tukey’s multiple comparison test. c LPS (100 ng/ml)-induced nitrite production was measured in BV-2 after PP2 (Src kinase inhibitor, 5 μM) or PDTC (ammonium pyrrolidinedithiocarbamate, NF-κB inhibitor, 20 μM) treatment for 24 h. d BV-2 cells were pretreated with 10 μM PTP1Bi or 10 μM PP2 for 1 h and then treated with LPS for 24 h as indicated. Nitrite levels were measured by Griess solution. e BV-2 cells were pretreated with PTP1Bi for 1 h and then treated with LPS (100 ng/ml) for 30 min. IκB degradation by LPS was measured by western blotting. IκB intensity was measured from four independent experiments and normalized to α-tubulin. The data were expressed as the mean ± SEM (n = 4). *p < 0.05 versus LPS only; analyzed by one-way ANOVA with Tukey’s multiple comparison test. f Diagram depicting a mechanism by which PTP1B may promote proinflammatory cytokine production. PTP1B activates Src through dephosphorylation of Y527. Src may activate NF-κB and increase the production of proinflammatory molecules. NS not significant