Structural insight into substrate and inhibitor discrimination by human P-glycoprotein

Area of Science:

• Structural Biology
• Biochemistry
• Pharmacology

Background:

• ABCB1 (P-glycoprotein) actively transports xenobiotics, contributing to multidrug resistance and hindering drug delivery.
• Understanding ABCB1 structure is crucial for developing effective cancer therapies.

Purpose of the Study:

• To determine the high-resolution cryo-electron microscopy structure of human ABCB1 bound to a substrate.
• To elucidate the structural mechanisms of ABCB1 inhibition and drug transport.

Main Methods:

• Cryo-electron microscopy (cryo-EM) at 3.5-angstrom resolution.
• Reconstitution of human ABCB1 in lipidic nanodiscs.
• Structural analysis of substrate-bound and inhibitor-bound ABCB1.

Main Results:

• A single paclitaxel molecule was observed in a central, occluded pocket of substrate-bound ABCB1.
• Two zosuquidar molecules occupied the same pocket in inhibitor-bound ABCB1.
• Structural plasticity in the drug-binding site influences nucleotide-binding domain dynamics.

Conclusions:

• The determined structures provide insights into ABCB1's drug-binding mechanism and transport.
• Membrane lipids like cholesterol modulate ABCB1 conformational changes.
• Findings aid in understanding and overcoming drug resistance mediated by ABCB1.