ABSTRACT
The discovery of the CNS-penetrant and selective alpha(2C) adrenergic receptor antagonist N-{2-[4-(2,3-dihydro-benzo[1,4]dioxin-2-ylmethyl)-[1,4]diazepan-1-yl]-ethyl}-2-phenoxy-nicotinamide, 13 is described. Structure-activity studies demonstrate the structural requirements for binding affinity, functional activity, and selectivity over other alpha(2)-AR subtypes.
Subject(s)
Adrenergic alpha-2 Receptor Antagonists , Azepines/chemical synthesis , Niacinamide/analogs & derivatives , Niacinamide/chemical synthesis , Animals , Azepines/pharmacology , Brain/metabolism , Central Nervous System/drug effects , Cerebrospinal Fluid/metabolism , Chemistry, Pharmaceutical/methods , Drug Design , Humans , Kinetics , Male , Molecular Conformation , Niacinamide/pharmacology , Rats , Rats, Inbred WKY , Receptors, Adrenergic, alpha-2/chemistry , Structure-Activity RelationshipABSTRACT
A-kinase anchoring proteins (AKAPs) have been proposed to regulate cAMP-dependent signaling in the cell by targeting RII subunits of protein kinase A (PKA) to specific subcellular compartments. RII(beta) is the predominant PKA subtype in adipose tissue. In gel overlay assays of C3H/10T1/2 adipocytes and adipose tissue, RII(beta) bound to several proteins including a prominent 132-kDa band, which was strongly induced upon differentiation of C3H/10T1/2 cells into adipocytes. Immunoblotting and nuclease protection analysis of C3H/10T1/2 cellular extracts identified this band as D-AKAP1/S-AKAP84, a putative AKAP. Immunocytochemical analysis of C3H/10T1/2 adipocytes revealed that most of D-AKAP1/S-AKAP84, but not RII(beta), was colocalized with a mitochondrial-selective dye, MitoTracker red. These findings were further confirmed in studies where D-AKAP1/ S-AKAP84, but not RII(beta), were localized in purified mitochondria made from C3H/10T1/2 adipocytes. Moreover, D-AKAP1, which is upregulated after differentiation, did not recruit RII(beta) to membrane fractions enriched in mitochondria. These results demonstrate that D-AKAP1/S-AKAP84 does not interact with PKA in differentiated C3H/10T1/2 adipocytes under the conditions tested.