Interactions between integrin αIIbβ3 and the serotonin transporter regulate serotonin transport and platelet aggregation in mice and humans
Ana Marin D. Carneiro, … , Dennis L. Murphy, Randy D. Blakely
Ana Marin D. Carneiro, … , Dennis L. Murphy, Randy D. Blakely
Published March 3, 2008
Citation Information: J Clin Invest. 2008;118(4):1544-1552. https://doi.org/10.1172/JCI33374.
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Research Article Hematology

Interactions between integrin αIIbβ3 and the serotonin transporter regulate serotonin transport and platelet aggregation in mice and humans

Abstract

The essential contribution of the antidepressant-sensitive serotonin (5-HT) transporter SERT (which is encoded by the SLC6A4 gene) to platelet 5-HT stores suggests an important role of this transporter in platelet function. Here, using SERT-deficient mice, we have established a role for constitutive SERT expression in efficient ADP- and thrombin-triggered platelet aggregation. Additionally, using pharmacological blockers of SERT and the vesicular monoamine transporter (VMAT), we have identified a role for ongoing 5-HT release and SERT activity in efficient human platelet aggregation. We have also demonstrated that fibrinogen, an activator of integrin αIIbβ3, enhances SERT activity in human platelets and that integrin αIIbβ3 interacts directly with the C terminus of SERT. Consistent with these findings, knockout mice lacking integrin β3 displayed diminished platelet SERT activity. Conversely, HEK293 cells engineered to express human SERT and an activated form of integrin β3 exhibited enhanced SERT function that coincided with elevated SERT surface expression. Our results support an unsuspected role of αIIbβ3/SERT associations as well as αIIbβ3 activation in control of SERT activity in vivo that may have broad implications for hyperserotonemia, cardiovascular disorders, and autism.

Authors

Ana Marin D. Carneiro, Edwin H. Cook, Dennis L. Murphy, Randy D. Blakely

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Figure 5

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

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ITGB3 Pro33 regulates SERT transport activity via serine/threonine prot...
(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.