Human Serotonin Transporter Coding Variation Establishes Conformational Bias with Functional Consequences.
Meagan A QuinlanDanielle KroutRania M KatamishMatthew J RobsonCatherine NettesheimPaul J GreschDeborah C MashL Keith HenryRandy D BlakelyPublished in: ACS chemical neuroscience (2019)
The antidepressant-sensitive serotonin (5-HT) transporter (SERT) dictates rapid, high-affinity clearance of the neurotransmitter in both the brain and periphery. In a study of families with multiple individuals diagnosed with autism spectrum disorder (ASD), we previously identified several, rare, missense coding variants that impart elevated 5-HT transport activity, relative to wild-type SERT, upon heterologous expression as well as in ASD subject lymphoblasts. The most common of these variants, SERT Ala56, located in the transporter's cytosolic N-terminus, has been found to confer in transgenic mice hyperserotonemia, an ASD-associated biochemical trait, an elevated brain 5-HT clearance rate, and ASD-aligned behavioral changes. Hyperfunction of SERT Ala56 has been ascribed to a change in 5-HT KM, though the physical basis of this change has yet to be elucidated. Through assessments of fluorescence resonance energy transfer (FRET) between cytosolic N- and C-termini, sensitivity to methanethiosulfonates, and capacity for N-terminal tryptic digestion, we obtain evidence for mutation-induced conformational changes that support an open-outward 5-HT binding conformation in vitro and in vivo. Aspects of these findings were also evident with another naturally occurring C-terminal SERT coding variant identified in our ASD study, Asn605. We conclude that biased conformations of surface resident transporters that can impact transporter function and regulation are an unappreciated consequence of heritable and disease-associated SERT coding variation.
Keyphrases
- energy transfer
- autism spectrum disorder
- intellectual disability
- attention deficit hyperactivity disorder
- single molecule
- quantum dots
- molecular dynamics simulations
- wild type
- molecular dynamics
- copy number
- endothelial cells
- white matter
- resting state
- poor prognosis
- mental health
- physical activity
- oxidative stress
- patient safety
- genome wide
- major depressive disorder
- cerebral ischemia
- multiple sclerosis
- working memory
- binding protein
- brain injury
- subarachnoid hemorrhage