ABSTRACT
Synthesis and derivatization of a series of substituted tetrahydrofluorenone analogs giving potent, ERbeta subtype selective ligands are described. Several analogs possessing ERbeta binding affinities comparable to 17beta-estradiol but with greater than 75-fold selectivity over ERalpha are reported.
Subject(s)
Estrogen Receptor beta/drug effects , Fluorenes/chemical synthesis , Fluorenes/pharmacology , Cell Line , Crystallography, X-Ray , Estrogen Receptor alpha/chemistry , Estrogen Receptor alpha/drug effects , Estrogen Receptor beta/chemistry , Fluorenes/classification , Humans , Ligands , Models, Molecular , Molecular Structure , Stereoisomerism , Structure-Activity RelationshipABSTRACT
Quinazolinone derivatives were synthesized and evaluated as non-peptidic growth hormone secretagogues. Modeling guided design of quinazolinone compound 21 led to a potency enhancement of greater than 200-fold compared to human growth hormone secretagogue affinity of a screening lead 4.
Subject(s)
Drug Design , Human Growth Hormone/metabolism , Quinazolines/chemical synthesis , Quinazolines/pharmacology , Receptors, Cell Surface/agonists , Receptors, G-Protein-Coupled , Animals , Binding Sites , Humans , Inhibitory Concentration 50 , Kinetics , Models, Molecular , Quinazolines/chemistry , Quinazolines/metabolism , Rats , Receptors, Cell Surface/metabolism , Receptors, Ghrelin , Secretory Rate/drug effects , Structure-Activity RelationshipABSTRACT
To investigate the mechanisms regulating polarized vesicle delivery to the cell surface in hepatocytes, we have characterized the endogenous plasma membrane (PM)-associated syntaxins. These integral membrane proteins are components of the membrane docking/fusion apparatus and are thought to function as vesicle receptors at the PM. In hepatocytes, the PM is divided into two domains, the apical and basolateral. If syntaxins are mediating the specific recognition of vesicles delivered to either membrane surface, the simple prediction is that each domain expresses one syntaxin isoform. However, we report that rat hepatocytes express three endogenous PM-associated syntaxin isoforms, syntaxins 2, 3 and 4. By biochemical subfractionation, we determined that the syntaxins exhibit distinct, but overlapping patterns of expression among the PM domains. Syntaxin 4 is primarily expressed at the basolateral surface while syntaxins 2 and 3 are enriched at the apical PM. The immunolocalization of syntaxins 2 and 4 in rat hepatocytes and PM sheets revealed similarly complex patterns of PM expression with enhanced apical staining for both. A significant proportion of syntaxin 3 (25%) was detected in subcellular fractions containing transport vesicles. We have used quantitative immunoblotting to determine that the syntaxins are relatively abundant PM molecules (11-260 nM) in rat liver, spleen and kidney. Also, we determined that the syntaxin binding protein, Munc-18, is present at concentrations from 1.5-20 nM in the same tissues. Although this fundamental quantitative and morphological information is lacking in other systems, it is critical not only for defining syntaxin function, but also for predicting the specific mechanisms that regulate vesicle targeting in hepatocytes and other tissues.
