Estudio de la influencia de los puentes disulfuro extracelulares del receptor 5-HT2A homodimérico en la farmacología antipsicótica

El receptor 5-HT2A es un GPCR que se encuentra ampliamente distribuido en el sistema nervioso central. Hasta la fecha, se ha descrito que existe en forma homodimérica, que heterodimeriza con otros GPCRs implicados en trastornos mentales como la esquizofrenia y que activa distintas vías de señalización intracelular. Sin embargo, el desconocimiento de las bases moleculares de su activación dificulta el diseño de fármacos dirigidos a esta diana. Su cristalización con los antipsicóticos zotepina y risperidona permitió determinar la importancia de los dominios extracelulares en la activación de dicho GPCR y, en particular, del puente disulfuro que conecta el dominio transmembrana 3 y el dominio extracelular 2. Por ello, en la presente tesis doctoral se desarrolló un modelo experimental que permitió estudiar la implicación de los puentes disulfuro extracelulares en la farmacología del receptor 5-HT2A, con dos aproximaciones: mediante el uso del agente reductor inespecífico DTT y mediante técnicas de mutagénesis dirigida

5-HT2 receptor binding, functional activity and selectivity in N-benzyltryptamines

The last fifteen years have seen the emergence and overflow into the drug scene of “superpotent” N-benzylated phenethylamines belonging to the “NBOMe” series, accompanied by numerous research articles. Although N-benzyl substitution of 5-methoxytryptamine is known to increase its affinity and potency at 5-HT2 receptors associated with psychedelic activity, N-benzylated tryptamines have been studied much less than their phenethylamine analogs. To further our knowledge of the activity of N-benzyltryptamines, we have synthesized a family of tryptamine derivatives and, for comparison, a few 5-methoxytryptamine analogs with many different substitution patterns on the benzyl moiety, and subjected them to in vitro affinity and functional activity assays vs. the human 5-HT2 receptor subtypes. In the binding (radioligand displacement) studies some of these compounds exhibited only modest selectivity for either 5-HT2A or 5-HT2C receptors suggesting that a few of them, with affinities in the 10–100 nanomolar range for 5-HT2A receptors, might presumably be psychedelic. Unexpectedly, their functional (calcium mobilization) assays reflected very different trends. All of these compounds proved to be 5-HT2C receptor full agonists while most of them showed low efficacy at the 5-HT2A subtype. Furthermore, several showed moderateto-strong preferences for activation of the 5-HT2C subtype at nanomolar concentrations. Thus, although some N-benzyltryptamines might be abuse-liable, others might represent new leads for the development of therapeutics for weight loss, erectile dysfunction, drug abuse, or schizophreniaThis work was supported by FONDECYT (Chile) regular research grants 1110146 and 1150868 to BKC and CONICYT doctoral grant 21140358 to MT-SS