Article

Role of Protein Transamidation in Serotonin-Induced Proliferation and Migration of Pulmonary Artery Smooth Muscle Cells

Rutgers University, Piscataway, New Jersey, USA.
American Journal of Respiratory Cell and Molecular Biology (Impact Factor: 3.99). 04/2011; 44(4):548-55. DOI: 10.1165/rcmb.2010-0078OC
Source: PubMed

ABSTRACT

Pulmonary hypertension is characterized by elevated pulmonary artery pressure and pulmonary artery smooth muscle cell (SMC) proliferation and migration. Clinical and experimental evidence suggests that serotonin (5-HT) is important in these responses. We previously demonstrated the participation of the 5-HT transporter and intracellular 5-HT (5-HTi) in the pulmonary vascular SMC-proliferative response to 5-HT. However, the mechanism underlying the intracellular actions of 5-HT is unknown. We speculated that 5-HTi activates SMC growth by post-translational transamidation of proteins via transglutaminase (TGase) activity, a process referred to as serotonylation. To test this hypothesis, serotonylation of pulmonary artery SMC proteins, and their role in 5-HT-induced proliferative and migratory responses, were assessed. 5-HT caused dose- and time-dependent increase in serotonylation of multiple proteins in both bovine and rat pulmonary artery SMCs. Inhibition of TGase with dansylcadaverin blocked this activity, as well as SMC-proliferative and migratory responses to 5-HT. Serotonylation of proteins also was blocked by 5-HT transporter inhibitors, and was enhanced by inhibition of monoamine oxidase, an enzyme known to degrade 5-HTi, indicating that 5-HTi levels regulate serotonylation. Immunoprecipitation assays and HPLC-mass spectral peptide sequencing revealed that a major protein serotonylated by TGase was fibronectin (FN). 5-HT-stimulated SMC serotonylation and proliferation were blocked by FN small interfering (si) RNA. These findings, together with previous observations that FN expression in the lung strongly correlates with the progression of pulmonary hypertension in both experimental animals and humans, suggest an important role of FN serotonylation in the pathogenesis of this disease.

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    • "There was no difference in the expression of epithelial cell TG2 between the OVAchallenged groups (Fig. 3B). Since TG2 catalyzes localized serotonin transamidation of glutamines (serotonylation) and this serotonylation regulates cell functions (25,41,45,59,67), we determined whether endothelial cell serotonylation is reduced during allergic inflammation in eTG2 / mice. Active, but not latent, TG2 catalyzes serotonylation (6, 36). "
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    ABSTRACT: Tissue transglutaminase 2 (TG2) is an enzyme with multiple functions, including catalysis of serotonin conjugation to proteins (serotonylation). Previous research indicates that TG2 expression is upregulated in human asthma and in the lung endothelium of OVA-challenged mice. It is not known whether endothelial TG2 is required for allergic inflammation. Therefore, to determine whether endothelial cell TG2 regulates allergic inflammation, mice with an endothelial cell-specific deletion of TG2 were generated, and then these mice were sensitized and challenged in the airways with OVA. Deletion of TG2 in endothelial cells blocked OVA-induced serotonylation in lung endothelial cells but not lung epithelial cells. Interestingly, deletion of endothelial TG2 reduced allergen-induced increases in respiratory system resistance, numbers of eosinophils in the BAL, and numbers of eosinophils in the lung tissue. Endothelial deletion of TG2 did not alter expression of adhesion molecules, cytokines or chemokines that regulate leukocyte recruitment, consistent with other studies, demonstrating that deletion of endothelial signals does not alter lung cytokines and chemokines during allergic inflammation. Taken together, the data indicate that endothelial cell TG2 is required for allergic inflammation by regulating the recruitment of eosinophils into OVA-challenged lungs. In summary, TG2 functions as a critical signal for allergic lung responses. These data identify potential novel targets for intervention in allergy/asthma. Copyright © 2015, American Journal of Physiology - Lung Cellular and Molecular Physiology.
    Full-text · Article · Jul 2015 · AJP Lung Cellular and Molecular Physiology
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    • "in the lung. TG is increased in allergic disease, TG catalyzes localized serotonin transamidation of glutamines (serotonylation), and serotonylation regulates cell functions (30, 65, 75, 93, 119). Therefore, we determined whether 5-HTP diets altered localized TG2 expression and serotonylation by immunolabeling lung tissue sections from mice inFig. "
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    ABSTRACT: Clinical reports indicate that patients with allergy/asthma commonly have associated symptoms of anxiety/depression. Anxiety/depression can be reduced by 5-hydroxytryptophan (5-HTP) supplementation. However, it is not known whether 5-HTP reduces allergic inflammation. Therefore, we determined whether 5-HTP supplementation reduces allergic inflammation. We also determined whether 5-HTP decreases passage of leukocytes through the endothelial barrier by regulating endothelial cell function. For these studies, C57BL/6 mice were supplemented with 5-HTP, treated with ovalbumin fraction V (OVA), house dust mite (HDM) extract, or IL-4, and examined for allergic lung inflammation and OVA-induced airway responsiveness. To determine whether 5-HTP reduces leukocyte or eosinophil transendothelial migration, endothelial cells were pretreated with 5-HTP, washed and then used in an in vitro transendothelial migration assay under laminar flow. Interestingly, 5-HTP reduced allergic lung inflammation by 70-90% and reduced antigen-induced airway responsiveness without affecting body weight, blood eosinophils, cytokines, or chemokines. 5-HTP reduced allergen-induced transglutaminase 2 (TG2) expression and serotonylation (serotonin conjugation to proteins) in lung endothelial cells. Consistent with the regulation of endothelial serotonylation in vivo, in vitro pretreatment of endothelial cells with 5-HTP reduced TNF-α-induced endothelial cell serotonylation and reduced leukocyte transendothelial migration. Furthermore, eosinophil and leukocyte transendothelial migration was reduced by inhibitors of transglutaminase and by inhibition of endothelial cell serotonin synthesis, suggesting that endothelial cell serotonylation is key for leukocyte transendothelial migration. In summary, 5-HTP supplementation inhibits endothelial serotonylation, leukocyte recruitment, and allergic inflammation. These data identify novel potential targets for intervention in allergy/asthma.
    Full-text · Article · Jul 2012 · AJP Lung Cellular and Molecular Physiology
    • "Serotonin through 5HT transporter (5HTT) is involved in pulmonary artery SMC and fibroblasts proliferation. Both 5HT transporter (5HTT) and 5HT receptors promote pulmonary artery SMC proliferation and migration, vasoconstriction and local microthrombi [175] [176]. In addition, 5HTT transactivates PDGF receptor in pulmonary artery SMC, indicating crosstalk between 5HT and PDGF pathways, both implicated in the pathogenesis of PH [177]. "
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