Structural basis for action by diverse antidepressants on biogenic amine transporters

• Published in: Nature (London) 2013-11, Vol.503 (7474), p.141-145
• Main Authors: Wang, Hui, Goehring, April, Wang, Kevin H., Penmatsa, Aravind, Ressler, Ryan, Gouaux, Eric
• Format: Article
• Language: English
• Subjects: 631/535/1266; 631/92/577; 631/92/612/1237; 82; Amino acids; Antidepressants; Antidepressants, Tricyclic; Antidepressive Agents, Second-Generation - metabolism; Antidepressive Agents, Second-Generation - pharmacology; Antidepressive Agents, Tricyclic - metabolism; Antidepressive Agents, Tricyclic - pharmacology; Bacterial Proteins - antagonists & inhibitors; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Binding sites; Binding, Competitive - drug effects; Biogenic amines; Biogenic Amines - metabolism; Carrier proteins; Chlorides - metabolism; Competition; Crystallography, X-Ray; Dopamine; Health aspects; Humanities and Social Sciences; Humans; Inhibitors; letter; Mazindol - metabolism; Mazindol - pharmacology; Models, Molecular; Molecular biology; multidisciplinary; Mutation; Neurotransmitters; Norepinephrine - metabolism; Pharmacology; Physiological aspects; Plasma Membrane Neurotransmitter Transport Proteins - antagonists & inhibitors; Plasma Membrane Neurotransmitter Transport Proteins - chemistry; Plasma Membrane Neurotransmitter Transport Proteins - genetics; Plasma Membrane Neurotransmitter Transport Proteins - metabolism; Protein Conformation - drug effects; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Reproducibility of Results; Science; Selective Serotonin Reuptake Inhibitors - metabolism; Selective Serotonin Reuptake Inhibitors - pharmacology; Serotonin Plasma Membrane Transport Proteins - chemistry; Serotonin Plasma Membrane Transport Proteins - genetics; Serotonin Plasma Membrane Transport Proteins - metabolism; Serotonin uptake inhibitors; Sertraline - metabolism; Sertraline - pharmacology; Sodium - metabolism; Structure-Activity Relationship
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature12648

LeuT, a bacterial homologue of eukaryotic biogenic amine transporters (BATs), is engineered to harbour human BAT-like pharmacology by the mutation of key residues around the primary binding pocket; this mutant is able to bind several classes of antidepressant drug with high affinity, helping to define their common mechanisms of action. Structural approach to antidepressant activity Neurotransmitter sodium symporters (NSSs) regulate endogenous neurotransmitter concentrations and are targets for a broad range of therapeutic agents, including selective serotonin reuptake inhibitors (SSRIs), serotonin–noradrenaline reuptake inhibitors (SNRIs) and tricyclic antidepressants (TCAs). An X-ray crystal structure of a eukaryotic NSS is not available, hindering our understanding of the mechanism of action of these antidepressants. In this manuscript, the authors used a bacterial homologue of NSSs as a scaffold to generate a hybrid protein with a pharmacological profile very similar to that of biogenic amine transporters. They solved X-ray crystal structures of these 'LeuBAT' variants in the presence of four SSRIs, two SNRIs, a TCA and the stimulant mazindol. Even though these compounds have very different chemical structures, they all bind at the same site of LeuBAT, thereby enabling the authors to better understand how SSRIs, SNRIs and TCAs bind to their eukaryotic NSS targets. The biogenic amine transporters (BATs) regulate endogenous neurotransmitter concentrations and are targets for a broad range of therapeutic agents including selective serotonin reuptake inhibitors (SSRIs), serotonin–noradrenaline reuptake inhibitors (SNRIs) and tricyclic antidepressants (TCAs) 1 , 2 . Because eukaryotic BATs are recalcitrant to crystallographic analysis, our understanding of the mechanism of these inhibitors and antidepressants is limited. LeuT is a bacterial homologue of BATs and has proven to be a valuable paradigm for understanding relationships between their structure and function 3 . However, because only approximately 25% of the amino acid sequence of LeuT is in common with that of BATs, and as LeuT is a promiscuous amino acid transporter 4 , it does not recapitulate the pharmacological properties of BATs. Indeed, SSRIs and TCAs bind in the extracellular vestibule of LeuT 5 , 6 , 7 and act as non-competitive inhibitors of transport 5 . By contrast, multiple studies demonstrate that both TCAs and SSRIs are competitive inhibitors for eukaryotic BATs and bind to the primary