Figure 5. ITGB3 Pro33 regulates SERT transport activity via serine/threonine protein phosphatases and p38 MAPK signaling.

(A) Coimmunoprecipitation experiment showing no changes in the SERT/αIIbβ3 complexes between SERT/Leu33 and SERT/Pro33 cells. (B) Reduction of SERT uptake activity in Pro33, but not Leu33, cells by inhibition of serine/threonine phosphatases. HEK293 cells expressing SERT and either Leu33 or Pro33 were incubated for 10 minutes with vehicle, okadaic acid (250 nM), or fostriecin (1 nM) before measurement of [³H]5-HT uptake. Data are presented as mean ± SEM. Paired Student’s t test: *P < 0.05, 1-way ANOVA with Dunnett’s post-test: ^###P < 0.0005, n = 6. (C) Coimmunoprecipitation experiment showing no changes in the SERT/PP2A complexes between Leu33 and Pro33 cells. (D) Reduction of SERT uptake activity in Pro33 by inhibition of p38 MAPK. HEK293 cells expressing SERT and either Leu33 or Pro33 were incubated for 10 minutes with SB203580 (20 μM) before measurement of [³H]5-HT uptake. Data are presented as mean ± SEM. Paired Student’s t test: *P < 0.05; 1-way ANOVA with Dunnett’s post-test: ^#P < 0.05; n = 6. (E and F) Enhanced p38 MAPK phosphorylation levels in Pro33 cells are sensitive to SB203580 and okadaic acid (250 nM). Data were normalized to total p38 MAPK levels and are presented as mean ± SEM. One-way ANOVA with Dunnett’s post-test: ^#P < 0.05; paired Student’s t test: **P < 0.01, ***P < 0.005; n = 3.