Computation-guided analysis of paroxetine binding to hSERT reveals functionally important structural elements and...

Area of Science:

• Neuroscience
• Structural Biology
• Pharmacology

Background:

• The serotonin transporter (SERT) is crucial for regulating serotonin levels and a key target for neuropsychiatric medications.
• Existing crystal structures of hSERT, while informative, are from mutated, non-transporting constructs, limiting mechanistic understanding.
• Paroxetine, a potent selective serotonin reuptake inhibitor (SSRI), binds to SERT but its precise interaction dynamics remain unclear.

Purpose of the Study:

• To investigate the functional implications of mutations in thermostabilized SERT constructs.
• To explore the binding dynamics and orientation of paroxetine within the SERT binding site.
• To elucidate the molecular basis for paroxetine's high affinity to SERT.

Main Methods:

• Extensive and comparative molecular dynamics (MD) simulations of SERT.
• Re-evaluation of transport and binding properties of thermostabilized SERT constructs.
• Analysis of structural elements perturbed by mutations and paroxetine binding.

Main Results:

• Identified functionally important structural elements affected by mutations in SERT constructs.
• Revealed unexpected dynamic behaviors within the central primary binding site of SERT.
• Uncovered potential ambiguity in the binding orientation of paroxetine to SERT.
• Proposed that favorable entropy contributes significantly to paroxetine's high affinity.

Conclusions:

• Mutations in thermostabilized SERT constructs alter functionally important regions.
• SERT exhibits dynamic behavior in its primary binding site, influencing inhibitor interactions.
• Entropy plays a critical role in the high affinity of paroxetine for SERT.
• Findings provide a foundation for mechanistic studies and rational design of novel SERT inhibitors.