Topic
Serotonectin
About: Serotonectin is a research topic. Over the lifetime, 2 publications have been published within this topic receiving 36 citations.
Papers
TL;DR: Data show that humans, like rats, have a circulating serotonin-binding glycoprotein that is also present as a peripheral membrane protein on platelets and the human also differs from the rat serotonectin in binding to white cells.
Abstract: A glycoprotein that circulates in blood, binds to the surface of platelets, and also binds serotonin with high avidity and specificity, has previously been found in rats. This glycoprotein has been called serotonectin. We now report the purification and characterization of a similar circulating glycoprotein in human blood that we propose be called human serotonectin, to distinguish it from the rat protein. Human serotonectin binds serotonin with high affinity (Kd1 = 36 nM; Kd2 = 1.1 microM). Monospecific antisera were raised in rabbits to purified human serotonectin. These antibodies were used to locate human serotonectin immunocytochemically, for quantitative estimation of the glycoprotein, and for rapid preparation of material purified by affinity chromatography. Evidence was obtained that indicated that human serotonectin circulates in plasma and also binds to the surfaces of white blood cells and platelets but not to red blood cells. In bone marrow it is found on megakaryocytes and on developing white cells of the eosinophil line. The protein can be completely removed by washing with isotonic sucrose or salt solutions from the surfaces of white cells but similar treatment only partially (63% sucrose wash/73% salt wash) removes human serotonectin from platelets. Antibodies to human serotonectin antagonize the uptake of serotonin by platelets but do not inhibit platelet aggregation. These data show that humans, like rats, have a circulating serotonin-binding glycoprotein that is also present as a peripheral membrane protein on platelets. The human also differs from the rat serotonectin in binding to white cells. The material may function in platelet serotonin uptake in both humans and rats; however, its function, if any, with respect to white cells is obscure.
26 citations
TL;DR: The data suggest that serotonectin is present on the external surface of platelet plasma membranes, that it is excluded from the plasma membrane of the surface connecting system, and that it may be in equilibrium with free material in plasma.
Abstract: Platelets, because of their ability to take up serotonin, are often considered as models of serotonergic neurons. We have purified a glycoprotein from rat platelets that specifically binds serotonin (KD = 10 nM) but not [3H]imipramine (up to 0.2 microM). This protein is distinct from fibronectin. Antiserum raised against this protein was shown to be monospecific by double diffusion, rocket immunoelectrophoresis and immunoreactivity of protein transferred from slab gels to nitrocellulose sheets. We have called this protein serotonectin. Serotonectin-like material was localized by light- and electron-microscopic immunocytochemistry in rat platelets, using the unlabelled peroxidase-antiperoxidase complex bridge technique. All serotonectin immunoreactivity was found to be associated with the plasma membrane but no immunoreactivity was found in the surface connecting system. Washing platelets with Krebs solution removed 75% of the extractable serotonectin, indicating that it is a peripheral protein. Serotonectin was found to be circulating in the plasma, as the ease of its removal from platelet membranes suggests it must do; however, none was found in brain synaptosomes. Serotonectin was found to be synthesized in blood-forming organs (spleen, bone marrow) but not in the liver or the mucosa of the gut. Antibodies to serotonectin (4.5 mg/ml) inhibited the uptake of [14H]serotonin (0.2 microM) by rat platelets but not by synaptosomes. Serotonectin did not bind [3H]imipramine and washing the protein off platelet membranes did not impede the binding of [3H]imipramine to the membranes. Thus an action on serotonectin does not seem to be responsible for the antagonism by tricyclic antidepressants of serotonin uptake. These data suggest that serotonectin is present on the external surface of platelet plasma membranes, that it is excluded from the plasma membrane of the surface connecting system, and that it may be in equilibrium with free material in plasma.
13 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 1985 | 1 |
| 1983 | 1 |