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ACS Omega Mar 2020A phenotypic whole cell high-throughput screen against the asexual blood and liver stages of the malaria parasite identified a benzimidazole chemical series. Among the...
A phenotypic whole cell high-throughput screen against the asexual blood and liver stages of the malaria parasite identified a benzimidazole chemical series. Among the hits were the antiemetic benzimidazole drug Lerisetron (IC NF54 = 0.81 μM) and its methyl-substituted analogue (IC NF54 = 0.098 μM). A medicinal chemistry hit to lead effort led to the identification of chloro-substituted analogue with high potency against the drug-sensitive NF54 (IC NF54 = 0.062 μM) and multidrug-resistant K1 (IC K1 = 0.054 μM) strains of the human malaria parasite . Compounds and gratifyingly showed in vivo efficacy in both and mouse models of malaria. Cardiotoxicity risk as expressed in strong inhibition of the human ether-a-go-go-related gene (hERG) potassium channel was identified as a major liability to address. This led to the synthesis and biological assessment of around 60 analogues from which several compounds with improved antiplasmodial potency, relative to the lead compound , were identified.
PubMed: 32258933
DOI: 10.1021/acsomega.0c00327 -
BMC Biochemistry Jun 2002The serotonin type 3 receptor (5-HT3R) is a member of a superfamily of ligand gated ion channels. All members of this family share a large degree of sequence homology...
BACKGROUND
The serotonin type 3 receptor (5-HT3R) is a member of a superfamily of ligand gated ion channels. All members of this family share a large degree of sequence homology and presumably significant structural similarity. A large number of studies have explored the structure-function relationships of members of this family, particularly the nicotinic and GABA receptors. This information can be utilized to gain additional insights into specific structural and functional features of other receptors in this family.
RESULTS
Thirteen amino acids in the mouse 5-HT3ASR that correspond to the putative E binding loop of the nicotinic alpha7 receptor were chosen for mutagenesis. Due to the presence of a highly conserved glycine in this region, it has been suggested that this binding loop is comprised of a hairpin turn and may form a portion of the ligand-binding site in this ion channel family. Mutation of the conserved glycine (G147) to alanine eliminated binding of the 5-HT3R antagonist [3H]granisetron. Three tyrosine residues (Y140, Y142 and Y152) also significantly altered the binding of 5-HT3R ligands. Mutations in neighboring residues had little or no effect on binding of these ligands to the 5-HT3ASR.
CONCLUSION
Our data supports a role for the putative E-loop region of the 5-HT3R in the binding of 5-HT, mCPBG, d-tc and lerisetron. 5-HT and mCPBG interact with Y142, d-tc with Y140 and lerisetron with both Y142 and Y152. Our data also provides support for the hypothesis that this region of the receptor is present in a loop structure.
Topics: Amino Acid Sequence; Amino Acids; Animals; Binding Sites; Cell Line; Humans; Kidney; Lysine; Mice; Molecular Sequence Data; Mutagenesis, Site-Directed; Protein Structure, Tertiary; Receptors, Serotonin; Receptors, Serotonin, 5-HT3; Sequence Alignment; Sequence Homology, Amino Acid; Transfection; Tyrosine
PubMed: 12079500
DOI: 10.1186/1471-2091-3-15 -
BMC Biochemistry Jun 2002Lerisetron, a competitive serotonin type 3 receptor (5-HT3R) antagonist, contains five functional groups capable of interacting with amino acids in the 5-HT3R binding...
BACKGROUND
Lerisetron, a competitive serotonin type 3 receptor (5-HT3R) antagonist, contains five functional groups capable of interacting with amino acids in the 5-HT3R binding site. Site directed mutagenesis studies of the 5-HT3AR have revealed several amino acids that are thought to form part of the binding domain of this receptor. The specific functional groups on the ligand that interact with these amino acids are, however, unknown. Using synthetic analogs of lerisetron as molecular probes in combination with site directed mutagenesis, we have identified some of these interactions and have proposed a model of the lerisetron binding site.
RESULTS
Two analogs of lerisetron were synthesized to probe 5-HT3R functional group interactions with this compound. Analog 1 lacks the N1 benzyl group of lerisetron and analog 2 contains oxygen in place of the distal piperazine nitrogen. Both analogs show significantly decreased binding affinity to wildtype 5-HT3ASRs. Mutations at W89, R91, Y142 and Y152 produced significant decreases in binding compared to wildtype receptors. Binding affinities of analogs 1 and 2 were altered only by mutations at W89, and Y152.
CONCLUSIONS
Based on the data obtained for lerisetron and analogs 1 and 2, we have proposed a tentative model of the lerisetron binding pocket of the 5-HT3ASR. According to this model, The N-benzyl group interacts in a weak interaction with R91 while the benzimidazole group interacts with W89. Our data support an interaction of the distal amino nitrogen with Y142 and Y152.
Topics: Animals; Arginine; Benzimidazoles; Benzyl Compounds; Cell Line; Humans; Kidney; Mice; Mutagenesis, Site-Directed; Nitrogen; Patch-Clamp Techniques; Piperazine; Piperazines; Piperidines; Protein Binding; Protein Interaction Mapping; Receptors, Serotonin; Receptors, Serotonin, 5-HT3; Serotonin Antagonists; Structure-Activity Relationship; Tryptophan; Tyrosine
PubMed: 12079499
DOI: 10.1186/1471-2091-3-16