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Autism‐linked Mutations in the Human Serotonin Transporter Induce Distinct Structural Changes that may Account for the Altered Function of the Transporter
Author(s) -
Krout Danielle,
Henry L. Keith
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.878.1
Subject(s) - serotonin transporter , transporter , serotonergic , serotonin , intracellular , phosphorylation , serotonin plasma membrane transport proteins , biology , chemistry , microbiology and biotechnology , biophysics , biochemistry , gene , receptor
Background Physiological studies show that 20–25% of individuals with autism spectrum disorder (ASD) exhibit elevated platelet serotonin (5‐HT) levels suggesting a link between regulation of the serotonergic system and behaviors associated with ASD. Furthermore, multiple ASD‐linked serotonin transporter (SERT) coding variants (ASVs) have been identified which augment 5‐HT transport function through enhanced catalytic activity (Gly56Ala and Lys605Asn) or elevated surface density (Ile425Leu, Phe465Leu, and Leu550Val). We propose that ASV‐induced hyperactivity is a result of altered SERT tertiary structure thereby affecting phosphorylation through the PKG and p38 MAPK signaling pathways and/or modulating plasmalemmal SERT turnover. Objective Identify SERT tertiary structure alterations mediated by ASV modifications that contribute to changes in catalytic activity or surface expression. Results We utilized the substituted cysteine accessibility method to assess conformational changes by comparing the sensitivity of one native (Cys109) and two engineered cysteine residues (Cys277 and Cys404) to methanethiosulfonate reagents (MTS). Cys277 displayed decreased reactivity in the ASVs Gly56Ala, Ile425Leu, Leu550Val, and Lys605Asn indicating reduced accessibility as a result of ASV‐induced conformational changes. Evaluation of reactivity changes at Cys109 and Cys404 is currently underway. In addition, we are characterizing structural changes in the ASVs after activation of the PKG or p38 MAPK pathways to determine if the functional changes stem from a common mechanism. Conclusion The reactivity changes we have observed at Cys277 support alteration of SERT tertiary structure by the ASVs Gly56Ala, Ile425Leu, Leu550Val, and Lys605Asn. In addition, t he intracellular position of the Cys277 probe in SERT and its decrease in MTS sensitivity suggests an ASV‐induced outward‐facing conformation.