TY - JOUR
T1 - Differential dynamics and direct interaction of bound ligands with lipids in multidrug transporter ABCG2
AU - Rasouli, Ali
AU - Yu, Qin
AU - Dehghani-Ghahnaviyeh, Sepehr
AU - Wen, Po Chao
AU - Kowal, Julia
AU - Locher, Kaspar P.
AU - Tajkhorshid, Emad
N1 - Funding Information:
ACKNOWLEDGMENTS. This study was supported by the NIH through the grants P41-GM104601andR01-GM123455,andbytheSwissNSFthroughtheNational Centre of Competence in Research (NCCR) TransCure, the Scientific Center for Optical and Electron Microscopy (ScopeM) at ETH Zürich for data collection support. Simulations were performed using allocations on Anton at Pittsburgh Supercomputing Center (award MCB100017P), NSF Supercomputing Centers (XSEDE grant number MCA06N060), and the Blue Waters Petascale Computing Facility of National Center for Supercomputing Applications at University of Illinois at Urbana-Champaign, which is supported by the NSF (awards OCI-0725070 and ACI-1238993) and the state of Illinois.
Publisher Copyright:
© 2022 the Author(s).
PY - 2023/1/3
Y1 - 2023/1/3
N2 - ABCG2 is an ATP-binding cassette (ABC) transporter that extrudes a wide range of xenobiotics and drugs from the cell and contributes to multidrug resistance in cancer cells. Following our recent structural characterization of topotecan-bound ABCG2, here, we present cryo-EM structures of ABCG2 under turnover conditions in complex with a special modulator and slow substrate, tariquidar, in nanodiscs. The structures reveal that similar to topotecan, tariquidar induces two distinct ABCG2 conformations under turnover conditions (turnover-1 and turnover-2). μs-scale molecular dynamics simulations of drug-bound and apo ABCG2 in native-like lipid bilayers, in both topotecan- and tariquidar-bound states, characterize the ligand size as a major determinant of its binding stability. The simulations highlight direct lipid-drug interactions for the smaller topotecan, which exhibits a highly dynamic binding mode. In contrast, the larger tariquidar occupies most of the available volume in the binding pocket, thus leaving little space for lipids to enter the cavity and interact with it. Similarly, when simulating ABCG2 in the apo inward-open state, we also observe spontaneous penetration of phospholipids into the binding cavity. The captured phospholipid diffusion pathway into ABCG2 offers a putative general path to recruit any hydrophobic/amphiphilic substrates directly from the membrane. Our simulations also reveal that ABCG2 rejects cholesterol as a substrate, which is omnipresent in plasma membranes that contain ABCG2. At the same time, cholesterol is found to prohibit the penetration of phospholipids into ABCG2. These molecular findings have direct functional ramifications on ABCG2's function as a transporter.
AB - ABCG2 is an ATP-binding cassette (ABC) transporter that extrudes a wide range of xenobiotics and drugs from the cell and contributes to multidrug resistance in cancer cells. Following our recent structural characterization of topotecan-bound ABCG2, here, we present cryo-EM structures of ABCG2 under turnover conditions in complex with a special modulator and slow substrate, tariquidar, in nanodiscs. The structures reveal that similar to topotecan, tariquidar induces two distinct ABCG2 conformations under turnover conditions (turnover-1 and turnover-2). μs-scale molecular dynamics simulations of drug-bound and apo ABCG2 in native-like lipid bilayers, in both topotecan- and tariquidar-bound states, characterize the ligand size as a major determinant of its binding stability. The simulations highlight direct lipid-drug interactions for the smaller topotecan, which exhibits a highly dynamic binding mode. In contrast, the larger tariquidar occupies most of the available volume in the binding pocket, thus leaving little space for lipids to enter the cavity and interact with it. Similarly, when simulating ABCG2 in the apo inward-open state, we also observe spontaneous penetration of phospholipids into the binding cavity. The captured phospholipid diffusion pathway into ABCG2 offers a putative general path to recruit any hydrophobic/amphiphilic substrates directly from the membrane. Our simulations also reveal that ABCG2 rejects cholesterol as a substrate, which is omnipresent in plasma membranes that contain ABCG2. At the same time, cholesterol is found to prohibit the penetration of phospholipids into ABCG2. These molecular findings have direct functional ramifications on ABCG2's function as a transporter.
KW - ABC transporters
KW - membrane proteins
KW - lipids
KW - molecular dynamics
KW - cryo-EM
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U2 - 10.1073/pnas.2213437120
DO - 10.1073/pnas.2213437120
M3 - Article
C2 - 36580587
SN - 0027-8424
VL - 120
SP - e2213437120
JO - Proceedings of the National Academy of Sciences
JF - Proceedings of the National Academy of Sciences
IS - 1
M1 - e2213437120
ER -