Significance: The imino acetamido moiety acts as an -amino acid bioisostere, as predicted by virtual screening.\n\nNMDA receptors are ligand-gated ion channels that mediate excitatory neurotransmission in the brain. They are tetrameric
complexes composed of glycine-binding GluN1 and GluN3 subunits together with glutamate-binding GluN2 subunits. Subunit-selective antagonists that discriminate between the glycine sites of GluN1 and GluN3 subunits would be valuable pharmacological PXD101 concentration tools for studies on the function and physiological roles of NMDA receptor subtypes. In a virtual screening for antagonists that exploit differences in the orthosteric binding site of GluN1 and GluN3 subunits, we identified a novel glycine site antagonist, 1-thioxo-1,2-dihydro-[1,2,4]triazolo[4,3-a]quinoxalin-4(5H)-one (TK40). Here, we show by Schild analysis that TK40 is a potent competitive antagonist with K-b values of 21-63 nm at the GluN1 glycine-binding site of the four recombinant GluN1/N2A-D receptors. In addition, TK40 displayed >100-fold selectivity for GluN1/N2 NMDA receptors over GluN3A- and GluN3B-containing NMDA receptors and no appreciable effects at AMPA receptors. Binding experiments BLZ945 on rat brain membranes and the purified GluN1 ligand-binding domain using glycine site GluN1 radioligands further confirmed the competitive
interaction and high potency. To delineate the binding mechanism, we have solved the crystal structure
of the GluN1 ligand-binding domain in complex with TK40 and show that TK40 binds to the orthosteric binding site of the GluN1 subunit with a binding mode that was also predicted by virtual screening. Furthermore, the structure reveals that the imino acetamido group of TK40 acts as an -amino acid bioisostere, which could be of importance in bioisosteric replacement strategies for future ligand design.”
“Theiler’s check details murine encephalomyelitis virus (TMEV), a member of the Cardiovirus genus in the family Picornaviridae, is a highly cytolytic virus that produces necrotic death in rodent cells except for macrophages, which undergo apoptosis. In the present study we have analyzed the kinetics of BeAn virus infection in M1-D cells, in order to temporally relate virus replication to the apoptotic signaling events. Apoptosis was associated with early exponential virus growth from 1 to 12 h postinfection (p.i.); however, >= 80% of peak infectivity was lost by 16 to 24 h p.i. The pan-caspase inhibitor qVD-OPh led to significantly higher virus yields, while zVAD-fmk completely inhibited virus replication until 10 h p.i., precluding its assessment in apoptosis. In contrast, while zVAD-fmk significantly inhibited BeAn virus replication in BHK-21 cells at 12 and 16 It p.i., virus replication at these time points was not altered by qVD-OPh.