ABSTRACT
We provided evidence for the formation of a novel phospholipase C-mediated calcium signal arising from coactivation of D1 and D2 dopamine receptors. In the present study, robust fluorescence resonance energy transfer showed that these receptors exist in close proximity indicative of D1-D2 receptor heterooligomerization. The close proximity of these receptors within the heterooligomer allowed for cross-phosphorylation of the D2 receptor by selective activation of the D1 receptor. D1-D2 receptor heterooligomers were internalized when the receptors were coactivated by dopamine or either receptor was singly activated by the D1-selective agonist (+/-)-6-chloro-7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide (SKF 81297) or the D2-selective agonist quinpirole. The D2 receptor expressed alone did not internalize after activation by quinpirole except when coexpressed with the D1 receptor. D1-D2 receptor heterooligomerization resulted in an altered level of steady-state cell surface expression compared with D1 and D2 homooligomers, with increased D2 and decreased D1 receptor cell surface density. Together, these results demonstrated that D1 and D2 receptors formed heterooligomeric units with unique cell surface localization, internalization, and transactivation properties that are distinct from that of D1 and D2 receptor homooligomers.
Subject(s)
Endocytosis , Receptors, Dopamine D1/agonists , Receptors, Dopamine D2/agonists , Animals , Biopolymers , Cell Line , Electrophoresis, Polyacrylamide Gel , Fluorescence Resonance Energy Transfer , Humans , Microscopy, Confocal , Radioligand Assay , Receptors, Dopamine D1/chemistry , Receptors, Dopamine D1/metabolism , Receptors, Dopamine D2/chemistry , Receptors, Dopamine D2/metabolismABSTRACT
Pneumomediastinum can result from blunt chest trauma in sports. Diagnosis is made using chest radiography. The natural history of isolated pneumomediastinum is benign; however, it can be associated with more serious injuries, such as disruption of the tracheobronchial tree or a perforated digestive viscus. Patients with isolated pneumomediastinum should be monitored with serial chest radiographs. Patients may return to full activity once their chest radiographs have returned to normal, they exhibit no symptoms, and they have regained their stamina.
