Synthesis and evaluation of novel N-alkylamine derivatives as high affinity sigma-1 receptor ligands

The sigma-1 receptor is a multidrug binding protein ubiquitously distributed in the mammalian tissues. While a singular biological function has not been attributed to the sigma-1 receptor, the consensus has been that the sigma-1 receptor plays an important role in membrane excitability and its regulation of cell growth and metabolism, perhaps through its chaperone activity. Several endogenous molecules have been suggested to bind and regulate the activity of the sigma-1 receptor including progesterone, N,N-dimethyltryptamine, and D-erythro-sphingosine.;The sigma-1 receptor binds to a number of pharmacologically important molecules. To explore the sigma-1 receptor binding characteristics for a class of small molecules with aliphatic hydrocarbon chain, this thesis has focused on the development of a number of N-alkylamine derivatives with varying chain length. Alkylation of Nalkylamines with either phenylpropyl or 4-nitrophenylpropyl substituents enhanced the affinities of the corresponding N-alkylamines at the sigma-1 receptor. Alternative targets determination of four of the eight N-alkylamine derivatives demonstrated selectivity of these compounds for the sigma receptors compared to over 40 other membrane receptors and transporters. Physiologically N-alkylamine derivatives promoted sigma-1 receptor mediated inhibition of potassium channels and were cytotoxic against a number of cancer cell lines as assessed with high throughput cytotoxicity assays.;A unique photochemistry of the N-(3-(4-nitrophenyl)propyl)alkan-1 -amines was discovered and is summarized in the second part of this thesis. The pure (and membrane bound) sigma-1 receptor photolyzed in the presence of 4-NPPC12 produced a second form that migrated 3 kDa faster on SDS-PAGE gels. Covalent modification by 4- NPPC12 at histidine 154 of the 23kDa form partly explained the anomalous gel shift pattern. Interestingly, the relative lack of protection of the light dependent 4-NPPC12- induced formation of the lower form of the sigma-1 receptor (23kDa) by some agonists compared to antagonists has provoked a two ligand-binding site model for the sigma-1 receptor.;The findings presented in this thesis contribute (1) towards an understanding of the "lipid-like" binding region of the sigma-1 receptor, (2) provide support for the idea that there are two ligand-binding sites on the sigma-1 receptor and (3) provide support for a hypothesis that the sigma-1 receptor may occur as a dimer.