Rap1GAP overexpression blocks the activation of Rap1 by CCK, carbachol,
and VIP. Acini were infected overnight with adenovirus expressing either
β-galactosidase (vector control) or Rap1GAP and then stimulated with 300
pm CCK (A), 10 μm carbachol (CCh),
and 10 nm VIP (B) for 10 min. An inhibition of Rap1
activation was observed when the Rap1GAP-overexpressing acini were stimulated
with CCK, carbachol, and VIP. The upper panel shows a representative
immunoblot for GTP-Rap1, total Rap1, or Rap1GAP. The lower panel
shows the quantitative analysis of Rap1 activation. Data shown are means
± S.E. (four experiments) for activation of Rap1 expressed as a
percentage of basal. **, p < 0.01; ***,
p < 0.001 versus basal; ††, p <
0.01; †††, p < 0.001 versus CCK,
carbachol, or VIP. C, to study the specificity of Rap1GAP, another
set of acini were stimulated with 1 nm CCK, and then a RhoA
pull-down assay was carried out; Rap1GAP overexpression did not affect
CCK-induced RhoA activation. The upper panel shows a representative
immunoblot for GTP-RhoA, total RhoA, or Rap1GAP. The lower panel
shows the quantitative analysis of RhoA activation. Data shown are means
± S.E. (three experiments) for activation of RhoA expressed as a
percentage of basal. *, p < 0.05 versus
basal.