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 1

Altered platelet aggregation in platelets with reduced SERT uptake and/or reduced granule content.

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Altered platelet aggregation in platelets with reduced SERT uptake and/o...
In vitro aggregation studies in SERT+/+, SERT +/–, and SERT–/– mouse platelets. Platelets were washed and exposed to either 20 μM ADP (A) or 0.05 U/ml thrombin (B). SERT-null mouse platelets have diminished aggregation response to ADP, as established by the analysis of initial aggregation rates. For A and B, bar plots represents mean ± SEM of 4 mice/genotype. (C) Depletion of granular pools of 5-HT by incubation with 10 nM reserpine (30 minutes at 37°C) dramatically reduces ADP-mediated (20 μM) aggregation in human platelets. (D) Acute SERT blockade by 4.5 μM citalopram reduces ADP-mediated platelet aggregation. Washed human platelets were incubated at 37°C for 10 minutes with citalopram or 1 mM GRGDSP peptide. n = 6. For A–D, final aggregation data represent mean ± SEM at t = 10 minutes. Rates are represented as mean ± SEM. One-way ANOVA with Dunnett’s post-test, *P < 0.05, **P < 0.01, and ***P < 0.005. (E) Confocal microscopy of human platelets plated on glass coverslips coated with fibrinogen. Platelets were preincubated with 10 μM 5-HT, 4.5 μM citalopram for 10 minutes, or 10 nM reserpine for 30 minutes at 37°C; seeded onto coverslips; and activated with 20 μM ADP. Images shown are representative of 4 independent experiments. Original magnification, ×65.