Activation of PAR1 increases TAB1 expression through a p38-dependent pathway. (A) PAR1 HeLa cells were pretreated for 30 min with DMSO, 5 µM SB203580, 20 µM SP600125, 10 µM U0126, or varying MG123 concentrations and then stimulated with 10 nM α-Th. TAB1 and TAB2 expression and p38 phosphorylation were then detected. The data (mean ± SD [error bars], n = 3) were analyzed using a Student’s t test (*, P < 0.05). (B) HUVECs were treated with 10 nM α-Th, and TAB1 expression was determined. The data (mean ± SD [error bars], n = 3) were analyzed using a Student’s t test (**, P < 0.01). (C) PAR1 HeLa cells were pretreated with DMSO or 5 µM SB203580 for 30 min and stimulated with 10 nM α-Th. Cell lysates were resolved on Phos-tag gels to detect TAB1 mobility (indicated by arrows) or SDS-PAGE to detect TAB1 and p38.