system
Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, OBJECTIVE, METHODS, RESULTS. Meshes: Cyclic AMP-Dependent Protein Kinases, G-Protein-Coupled Receptor Kinase 2, HEK293 Cells, Hedera, Humans, Isoproterenol, Oleanolic Acid, Phosphorylation, Receptors, Adrenergic, beta-2, Recombinant Fusion Proteins, Saponins, Signal Transduction.
user
Does α-Hederin inhibit G protein-coupled receptor kinase 2-mediated phosphorylation of β2-adrenergic receptors? Context: Recently is has been shown that α- and β-hederin increase the β2-adrenergic responsiveness of alveolar type II cells (A549) and human airway smooth muscle cells (HASM), respectively, by inhibiting the internalization of β2-adrenergic receptors (β2AR) under stimulating conditions. Internalization of β2AR is initiated by phosphorylations of certain serines and threonines by cAMP dependent protein kinase A (PKA) and G protein-coupled receptor kinases (GRK). To evaluate the effect of α-hederin on PKA and GRK2 mediated phosphorylation of GFP-tagged β2AR. To study this process we performed In-Cell Western using isoprenaline stimulated HEK293 cells overexpressing β2AR as GFP fusion protein and specific antibodies against PKA (Ser345/346) and GRK2 (Ser355/356) phosphorylation sites. There was no effect found on the PKA mediated phosphorylation (n = 14) but we could show that α-hederin (1 µM, 12 h) significantly inhibits GRK2 mediated phosphorylation at Ser355/356 by 11 ± 5% (n ≥ 29, p ≤ 0.01) under stimulating conditions compared to the positive control. In Förster resonance energy transfer (FRET) experiments using the isolated kinases in solution α-hederin did not show any influence neither to GRK2 nor to PKA.
assistant
Taken together, these results indicate that α-hederin acts as an indirect GRK2 inhibitor leading to a reduced homologous desensitization of β2AR-GFP in HEK293 cells. Final Decision: yes