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Background/Aims: Signaling of Gs protein-coupled receptors (GsPCRs) is accomplished by stimulation of adenylyl cyclase, causing an increase of the intracellular cAMP concentration, activation of the intracellular cAMP effectors protein kinase A (PKA) and Epac, and an efflux of cAMP, the function of which is still unclear.
Methods: Activation of adenylyl cyclase by GsPCR agonists or cholera toxin was monitored by measurement of the intracellular cAMP concentration by ELISA, anti-phospho-PKA substrate motif phosphorylation by immunoblotting, and an Epac-FRET assay in the presence and absence of adenosine receptor antagonists or ecto-nucleotide phosphodiesterase/pyrophosphatase2 (eNPP2) inhibitors. The production of AMP from cAMP by recombinant eNPP2 was measured by HPLC. Extracellular adenosine was determined by LC-MS/MS, extracellular ATP by luciferase and LC-MS/MS. The expression of eNPP isoenzymes 1-3 was examined by RT-PCR. The expression of multidrug resistance protein 4 was suppressed by siRNA.
Results: Here we show that the activation of GsPCRs and the GsPCRs-independent activation of Gs proteins and adenylyl cyclase by cholera toxin induce stimulation of cell surface adenosine receptors (A2A or A2B adenosine receptors). In PC12 cells stimulation of adenylyl cyclase by GsPCR or cholera toxin caused activation of A2A adenosine receptors by an autocrine signaling pathway involving cAMP efflux through multidrug resistance protein 4 and hydrolysis of released cAMP to AMP by eNPP2. In contrast, in PC3 cells cholera toxin- and GsPCR-induced stimulation of adenylyl cyclase resulted in the activation of A2B adenosine receptors.
Conclusion: Our findings show that stimulation of adenylyl cyclase causes a remarkable activation of cell surface adenosine receptors.
As insect decline threatens the fauna of Central Europe, “dark taxa” present an obstacle to understanding biodiversity loss. The superfamily Platygastroidea is a dark taxon, with many superficial descriptions requiring examination of type material to characterize and revise species and genera. The Natural History Museum Vienna (Naturhistorisches Museum Wien) is arguably the most important historical collection of Platygastroidea in Central Europe. Type specimens from 85 species in 21 genera and three families are here catalogued and photographically illustrated, including previously undocumented types described by Förster, Kieffer, Nees von Esenbeck, and Ratzeburg. Lectotypes are designated for Anteris bicolor Kieffer, Anteris simulans Kieffer, Hadronotus laticeps Kieffer, Leptacis foersteri Kieffer, Plastogryon investis Kieffer, Plastogryon sagax Kieffer, Prophanurus mayri Kieffer, and Telenomus laeviceps Förster. Trissolcus schimitsheki (Szelényi) syn. nov. is treated as a junior synonym of Trissolcus scutellaris (Thomson) and Telenomus nomas Förster syn. nov. is treated as a junior synonym of Trissolcus semistriatus (Nees). Baeus maculatus (Förster) comb. nov. is transferred from Telenomus. Historical, taxonomic, and curatorial remarks are included, providing an essential foundation for revisionary work on the Platygastroidea of Central Europe and beyond.