New Insights into the Binding Mechanism of Co-regulator BUD31 to AR AF2 Site: Structural Determination and Analysis of the Mutation Effect

Abstract

Introduction: Androgen Receptor (AR) plays a pivotal role in the development of male sex and contributes to prostate cancer growth. Different from other nuclear receptors that bind to the co-regulator LxxLL motif in coregulator peptide interaction, the AR Ligand Binding Domain (LBD) prefers to bind to the FxxLF motif. BUD31, a novel co-regulator with FxxLF motif, has been demonstrated to suppress wild-type and mutated AR-mediated prostate cancer growth.

Methods: To find out the interaction mechanisms of BUD31 with WT/T877A/W741L AR complex, molecular dynamics simulations were employed to study the complex BUD31 and WT/mutant ARs. The molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) results demonstrated that T877A and W741L point mutations can reduce the binding affinity between BUD31 and AR. The RMSF and dynamic cross-correlation analysis indicated that amino acid point mutations can affect the motions of loop residues in the AR structure.

Results: These results indicated that AR co-regulator binding site AF2 can serve as a target for drug discovery to solve the resistance problem.

Keywords: AF2 binding site; BUD31; Androgen receptor; co-regulator; interaction mechanism; molecular dynamics..

Fig. (1)

The structure of wild type AR and peptide BUD31. a: The Ribbon structure of WT AR-BUD31 complex. b: The surface of WT AR-BUD31 complex. c: The active site of WT AR.

Fig. (2)

The time evolution of the RMSD values of the backone atoms of the BUD31-WT/mutant AR.

Fig. (3)

RMSF values for wild type AR and its mutants. The Root Mean Square Fluctuation (RMSF) for Cα atoms of wild type AR-BUD31 and its mutants relative to the initial structure were calculated.

Fig. (4)

Cross-correlation matrices of the fluctuations of coordinates for Cα atoms around their mean positions during the last 10 ns of MD simulation. The extent of correlated motions and anticorrelated motions are color-coded. a: WT-BUD31. b: T877A-BUD31. c: W741L-BUD31.

Fig. (5)

The residues contribution of AR to BUD31 binding. a: per residue contribution profile for ΔGele. b: per residue contribution profile for ΔGpol. c: per residue contribution profile for ΔG.

Fig. (6)

The average structures of WT and its mutants take from the last 10 ns of the molecular dynamics simulations with the key residues of the binding pocket of the complexes. a: WT-BUD31. b: T877A-BUD31. c: W741L-BUD31.

Fig. (7)

The hydrophobic surfaces of the complexes of WT and its mutants: a: WT-BUD31. b: T877A-BUD31. c: W741L-BUD31. Herein, orange represents hydrophobic regions, whereas blue represents hydrophilic regions.