Imidazopyridyl compounds as aldosterone synthase inhibitors.

The inhibition of aldosterone synthase (CYP11B2) may be an effective treatment of hypertension and heart failure, among other ailments. Previously reported benzimidazole CYP11B2 inhibitors led the way for bioisosteric imidazopyridines that are both potent and selective over CYP11B1.

Identification of Leu276 of the S1P1 receptor and Phe263 of the S1P3 receptor in interaction with receptor specific agonists by molecular modeling, site-directed mutagenesis, and affinity studies.

Sphingosine-1-phosphate (S1P) receptor agonists are novel immunosuppressive agents. The selectivity of S1P1 against S1P3 is strongly correlated with lymphocyte sequestration and minimum acute toxicity and bradycardia. This study describes molecular modeling, site-directed mutagenesis, and affinity studies exploring the molecular basis for selectivity between S1P1 and S1P3 receptors. Computational models of human S1P1 and S1P3 receptors bound with two nonselective agonists or two S1P1-selective agonists were developed based on the X-ray crystal structure of bovine rhodopsin. The models predict that S1P1 Leu276 and S1P3 Phe263 contribute to the S1P1/S1P3 selectivity of the two S1P1-selective agonists. These residues were subjected to site-directed mutagenesis. The wild-type and mutant S1P receptors were expressed in Chinese hamster ovary cells and examined for their abilities to bind to and be activated by agonists in vitro. The results indicate that the mutations have minimal effects on the activities of the two nonselective agonists, although they have dramatic effects on the S1P1-selective agonists. These studies provide a fundamental understanding of how these two receptor-selective agonists bind to the S1P1 and S1P3 receptors, which should aid development of more selective S1P1 receptor agonists with immunosuppressive properties and improved safety profiles.

Molecular characterization of the murine SIGNR1 gene encoding a C-type lectin homologous to human DC-SIGN and DC-SIGNR.

The C-type lectin human dendritic cell (DC)-specific intercellular adhesion molecule (ICAM)-3-grabbing non-integrin (DC-SIGN) plays important roles in pattern recognition by dendritic cells in the immune system. In addition to binding human immunodeficiency virus (HIV), this type II membrane protein binds with high affinity to the adhesion molecules ICAM-3 and -2 to promote important dendritic cell interactions with naive T cells and endothelial cells, respectively. DC-SIGNR, a human DC-SIGN homologue expressed on sinusoidal endothelial cells in liver and lymph node, also binds and transmits HIV virus. We describe the cloning and characterization of a family of murine complementary DNAs (cDNAs) called SIGNR1, expressed in skin and spleen, that encode C-type lectins highly related to human DC-SIGN and DC-SIGNR. We also report the genomic structure of the SIGNR1 gene and compare it to that of human DC-SIGN and DC-SIGNR. The different transcripts (alpha, beta, gamma, delta) are generated by differences in 5' untranslated sequences, alternative splicing and/or the use of different polyadenylation sites. The predicted open reading frames encoded by the cDNAs are most closely related to human DC-SIGN and DC-SIGNR in the cytoplasmic domain, the transmembrane region and the carbohydrate recognition domain. Moreover, the alternatively spliced transcripts encode proteins that lack the transmembrane region or have modified carbohydrate recognition domains. Northern hybridization experiments with several different SIGNR1 cDNA probes reveal transcripts of 1.3 and 2.1 kb that are expressed in a tissue-restricted fashion in murine skin, spleen and lung. In situ hybridization and immunocytochemistry experiments demonstrate that, like human DC-SIGN, the murine messenger RNAs are expressed in subsets of dendritic cells in the spleen and skin.