6 research outputs found
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Coupling to Gq Signaling Is Required for Cardioprotection by an Alpha-1A-Adrenergic Receptor Agonist
RationaleGq signaling in cardiac myocytes is classically considered toxic. Targeting Gq directly to test this is problematic, because cardiac myocytes have many Gq-coupled receptors.ObjectiveTest whether Gq coupling is required for the cardioprotective effects of an alpha-1A-AR (adrenergic receptor) agonist.Methods and resultsIn recombinant cells, a mouse alpha-1A-AR with a 6-residue substitution in the third intracellular loop does not couple to Gq signaling. Here we studied a knockin mouse with this alpha-1A-AR mutation. Heart alpha-1A receptor levels and antagonist affinity in the knockin were identical to wild-type. In wild-type cardiac myocytes, the selective alpha-1A agonist A61603-stimulated phosphoinositide-phospholipase C and myocyte contraction. In myocytes with the alpha-1A knockin, both A61603 effects were absent, indicating that Gq coupling was absent. Surprisingly, A61603 activation of cardioprotective ERK (extracellular signal-regulated kinase) was markedly impaired in the KI mutant myocytes, and A61603 did not protect mutant myocytes from doxorubicin toxicity in vitro. Similarly, mice with the α1A KI mutation had increased mortality after transverse aortic constriction, and A61603 did not rescue cardiac function in mice with the Gq coupling-defective alpha-1A receptor.ConclusionsGq coupling is required for cardioprotection by an alpha-1A-AR agonist. Gq signaling can be adaptive
Structural Basis of Small-Molecule Aggregate Induced Inhibition of a Protein–Protein Interaction
A prevalent observation
in high-throughput screening and drug discovery
programs is the inhibition of protein function by small-molecule compound
aggregation. Here, we present the X-ray structural description of
aggregation-based inhibition of a protein–protein interaction
involving tumor necrosis factor α (TNFα). An ordered conglomerate
of an aggregating small-molecule inhibitor (JNJ525) induces a quaternary
structure switch of TNFα that inhibits the protein–protein
interaction between TNFα and TNFα receptors. SPD-304 may
employ a similar mechanism of inhibition