Comprehensive Characterization of LAT1 Cholesterol-Binding Sites

Area of Science:

• Biochemistry
• Structural Biology
• Computational Biophysics

Background:

• Human L-type amino acid transporter 1 (LAT1; SLC7A5) is crucial for amino acid homeostasis in vital tissues like the blood-brain barrier.
• Cholesterol is known to modulate membrane transporter activity, but its specific interactions with LAT1 remain poorly understood.
• A recent cryo-EM structure revealed potential cholesterol-binding sites on LAT1.

Purpose of the Study:

• To computationally investigate the role of cholesterol in the structure and function of LAT1.
• To identify and characterize specific cholesterol-binding sites on LAT1.
• To elucidate the molecular mechanisms by which cholesterol influences LAT1 conformation and activity.

Main Methods:

• Comprehensive computational analysis including molecular dynamics (MD) simulations.
• Molecular docking and MM/GBSA free energy calculations were employed.
• Principal component analysis (PCA) and center of mass (COM) distance assessments were utilized.

Main Results:

• Cholesterol binding site CHOL3 demonstrated the most stable and favorable interactions with LAT1.
• CHOL3 binding was shown to stabilize the inward-open conformation of LAT1 by maintaining domain integrity.
• An alternative binding site for the previously identified CHOL1 was proposed.

Conclusions:

• Cholesterol plays a significant role in stabilizing the LAT1 transporter, particularly through the CHOL3 site.
• This study enhances the understanding of cholesterol's allosteric modulation of LAT1.
• Identified binding sites offer potential targets for the rational design of novel allosteric ligands for LAT1.