ABSTRACT
Omega-conotoxin MVIIA, a highly potent antagonist of the N-type voltage sensitive calcium channel, has shown utility in several models of pain and ischemia. We report a series of three alkylphenyl ether based analogues which mimic three key amino acids of the toxin. Two of the compounds have been found to exhibit IC50 values of 2.7 and 3.3 microM at the human N-type voltage sensitive calcium channel.
Subject(s)
Phenyl Ethers/chemistry , Phenyl Ethers/pharmacology , omega-Conotoxins/chemistry , omega-Conotoxins/pharmacology , Animals , Calcium Channel Blockers/chemical synthesis , Calcium Channel Blockers/chemistry , Calcium Channel Blockers/pharmacology , Calcium Channels, L-Type , Calcium Channels, N-Type , Drug Evaluation , Inhibitory Concentration 50 , Models, Molecular , Mollusk Venoms/chemical synthesis , Mollusk Venoms/chemistry , Mollusk Venoms/pharmacology , Muscle, Smooth/chemistry , Muscle, Smooth/cytology , Phenyl Ethers/chemical synthesis , Rats , Rats, Inbred Strains , Snails/chemistry , Structure-Activity Relationship , omega-Conotoxins/chemical synthesisSubject(s)
Drug Design , GTP-Binding Proteins/metabolism , Models, Molecular , Mutation , Protein Conformation , Receptors, Cell Surface/chemistry , Receptors, Cell Surface/genetics , Animals , Bacteriorhodopsins/chemistry , Bacteriorhodopsins/metabolism , Humans , Ligands , Receptors, Biogenic Amine/chemistry , Receptors, Biogenic Amine/metabolism , Receptors, Cell Surface/metabolism , Receptors, Cell Surface/physiology , Receptors, Peptide/chemistry , Receptors, Peptide/metabolism , Rhodopsin/chemistry , Rhodopsin/metabolism , Signal Transduction/physiologyABSTRACT
Three-dimensional molecular models of the human melanocortin receptor (hMC1R) have been developed based upon the electron cryo-microscopic structure of bacteriorhodopsin and the electron density footprint of bovine rhodopsin. alpha-Melanocyte-stimulating hormone, Ac-Ser-Tyr-Ser-Met4-Glu-His-Phe7-Arg-Trp-Gly-Lys-Pro-Val-NH2 (alpha-MSH, alpha-melanotropin), and the superpotent, prolonged acting agonists, Ac-Ser-Tyr-Ser-Nle4-Glu-His-DPhe7-Arg-Trp-Gly-Lys-Pro-Val-NH2 (NDP-MSH) and Ac-Nle4-c[Asp5-His6-DPhe7-Arg8-Trp9-Lys10]-NH2 (MTII), have been modeled into the proposed binding sites with specific ligand-receptor interactions identified. The melanotropin sidechain pharmacophores, DPhe7 and Trp9, are proposed to interact with a hydrophobic network of receptor aromatic residues in transmembrane regions 4, 5, 6, and 7. In addition, a hydrophilic network involving the ligand Arg8 and polar receptor residues located in transmembrane regions 2 and 3 were identified. Biological studies on alpha-MSH, NDP-MSH, MTII, and related peptides have been correlated with the proposed hMC1R model in terms of agonism, affinity, and prolongation. Finally, limited MC1R mutagenesis studies comparing alpha-MSH and NDP-MSH are interpreted within the context of the proposed hMC1R models.
Subject(s)
Melanocyte-Stimulating Hormones/agonists , Peptides/chemistry , Peptides/metabolism , Receptors, Corticotropin/chemistry , Receptors, Corticotropin/metabolism , Amino Acid Sequence , Animals , Bacteriorhodopsins/chemistry , Cattle , Humans , Models, Molecular , Molecular Sequence Data , Oligopeptides/chemistry , Oligopeptides/pharmacology , Protein Conformation , Protein Structure, Secondary , Receptors, Melanocortin , Rhodopsin/chemistry , Sequence Homology, Amino Acid , Structure-Activity Relationship , Templates, Genetic , alpha-MSH/analogs & derivatives , alpha-MSH/chemistry , alpha-MSH/metabolism , alpha-MSH/pharmacologyABSTRACT
We report the first large-scale systematic quantitative structure-activity relationship (QSAR) study of barbiturates, correlating molecular structures with anticonvulsant activity. To achieve this QSAR study, we devised a four-step strategy. In step 1, an optimal quantum mechanical technique for determining the geometry and shape (conformation) of barbiturates was ascertained; this is the AM1 semiempirical molecular orbital method. In step 2, the AM1 method was used to optimize the structures and molecular properties of 48 barbiturates with varying anticonvulsant activity. In step 3, discriminant analysis and regression analysis statistical calculations were used to correlate the molecular properties of the 48 analogues against maximal electroshock (MES) and subcutaneous metrazol (s.c.Met)-induced seizures. In step 4, the contribution of molecular electrostatic properties to barbiturate anticonvulsant activity was further refined by quantum mechanical derived molecular electrostatic potential (MEP) maps. Using this four-step strategy, we defined the pharmacophore, the portion of a molecule responsible for bioactivity, for anti-MES and anti-s.c.Met activity. For anti-s.c.Met activity, barbiturate lipophilicity and geometry are important considerations; for anti-MES activity, barbiturate topologic and electronic properties have increased relevance.
Subject(s)
Anticonvulsants , Barbiturates/pharmacology , Drug Design , Discriminant Analysis , Humans , Mathematics , Models, Molecular , Molecular Conformation , Molecular Structure , Structure-Activity RelationshipABSTRACT
Various semicarbazones derived from aryl aldehydes, phenylalkyl aldehydes, and phenylalkyl ketones as well as some related compounds were evaluated for anticonvulsant activity. Most of the compounds displayed anticonvulsant activity in the maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) screens accompanied by neurotoxicity when given to mice by the intraperitoneal route. However quantitative data revealed protection indices (TD50/ED50) of less than 4 in general. Oral administration of the compounds to rats led to excellent potency in the MES screen accompanied by high protection indices while virtually no activity in the scPTZ test was displayed. These observations support the theory that one large hydrophobic group (in this case the aryl ring) and two electron donor atoms (present in the semicarbazono group) are requirements for protection in the MES screen. In general, the semicarbazones had rapid onsets of action, and one of the ways in which these compounds displayed their anticonvulsant activity is likely to be interaction with chloride channels. Empirical and semiempirical conformational calculations indicated that certain molecular fragments and hydrophobicity of these molecules affect bioactivity.
