β-Arrestin2 signaling stimulates Mnk1 activation and protein
synthesis in vascular smooth muscle cells. A, rVSMCs were
serum-starved and pretreated with vehicle Me2SO (DMSO),
the PKC inhibitor Ro31–8425, or the MEK inhibitor U0126 for 30 min.
Cells were stimulated with either 100 nm AngII (A) or 10
μm SII-AngII (S) for an additional 30 min. Western
blots for pMnk1 were performed and quantitated. Results depicted are
representative of four experiments ± S.E. Statistical significance was
calculated using a one-way ANOVA with post test.
Me2SO-nonstimulated was compared with the following,
Me2SO AngII (**, p < 0.01), Me2SO
SII (*, p < 0.05), Ro31 AngII (***,
p < 0.001), and Ro31 SII (**, p < 0.01). No
other conditions are significant with respect to the
Me2SO-nonstimulated group. B, rVSMCs were transfected with
siRNA for β-arr2 and subjected to pMnk1 analysis as in A at 96 h
post-transfection. Graph depicts results from six experiments ± S.E.
Statistical significance was calculated using a one-way ANOVA with post test.
CTL-nonstimulated was compared with CTL AngII (***, p <
0.001) and CTL SII (**, p < 0.01). CTL AngII was
compared with βarr2 AngII (**, p < 0.01). No other
comparisons are significant. C, rat vascular smooth muscle cells
(rVSMC) were serum-starved and stimulated with AngII or SII in the presence of
[3H]leucine for 24 h. Radiolabeled proteins were quantitated as
described under “Experimental Procedures.” Data are normalized
such that nonstimulated cells are set to 100%. Results depicted are
representative of four experiments (means ± S.E.). Statistical
significance was calculated using a one-way ANOVA with post test: N.S.
versus AngII was *, p < 0.01 and N.S.
versus SII was **, p < 0.05. D, rVSMC
were transfected with siRNAs for β-arrestin2 or Mnk1 and subjected to
protein synthesis analysis as in C at 96 h post-transfection. Results
depicted are representative of six experiments (means ± S.E.).
Statistical significance was calculated using a one-way ANOVA with post test.
CTL N.S. compared with CTL AngII was *, p < 0.05. CTL
AngII compared with βarr2 AngII and Mnk1 AngII were both **,
p < 0.01.