51
|
Cheng MH, Block E, Hu F, Cobanoglu MC, Sorkin A, Bahar I. Insights into the Modulation of Dopamine Transporter Function by Amphetamine, Orphenadrine, and Cocaine Binding. Front Neurol 2015; 6:134. [PMID: 26106364 PMCID: PMC4460958 DOI: 10.3389/fneur.2015.00134] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 05/26/2015] [Indexed: 12/29/2022] Open
Abstract
Human dopamine (DA) transporter (hDAT) regulates dopaminergic signaling in the central nervous system by maintaining the synaptic concentration of DA at physiological levels, upon reuptake of DA into presynaptic terminals. DA translocation involves the co-transport of two sodium ions and the channeling of a chloride ion, and it is achieved via alternating access between outward-facing (OF) and inward-facing states of DAT. hDAT is a target for addictive drugs, such as cocaine, amphetamine (AMPH), and therapeutic antidepressants. Our recent quantitative systems pharmacology study suggested that orphenadrine (ORPH), an anticholinergic agent and anti-Parkinson drug, might be repurposable as a DAT drug. Previous studies have shown that DAT-substrates like AMPH or -blockers like cocaine modulate the function of DAT in different ways. However, the molecular mechanisms of modulation remained elusive due to the lack of structural data on DAT. The newly resolved DAT structure from Drosophila melanogaster opens the way to a deeper understanding of the mechanism and time evolution of DAT–drug/ligand interactions. Using a combination of homology modeling, docking analysis, molecular dynamics simulations, and molecular biology experiments, we performed a comparative study of the binding properties of DA, AMPH, ORPH, and cocaine and their modulation of hDAT function. Simulations demonstrate that binding DA or AMPH drives a structural transition toward a functional form predisposed to translocate the ligand. In contrast, ORPH appears to inhibit DAT function by arresting it in the OF open conformation. The analysis shows that cocaine and ORPH competitively bind DAT, with the binding pose and affinity dependent on the conformational state of DAT. Further assays show that the effect of ORPH on DAT uptake and endocytosis is comparable to that of cocaine.
Collapse
Affiliation(s)
- Mary Hongying Cheng
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA
| | - Ethan Block
- Department of Cell Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA
| | - Feizhuo Hu
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA ; Department of Pharmacology and Pharmaceutical Sciences, School of Medicine, Tsinghua University , Beijing , China
| | - Murat Can Cobanoglu
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA
| | - Alexander Sorkin
- Department of Cell Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA
| | - Ivet Bahar
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA , USA
| |
Collapse
|
52
|
Functional mechanisms of neurotransmitter transporters regulated by lipid-protein interactions of their terminal loops. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:1765-74. [PMID: 25847498 DOI: 10.1016/j.bbamem.2015.03.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 03/16/2015] [Accepted: 03/23/2015] [Indexed: 01/28/2023]
Abstract
The physiological functions of neurotransmitter:sodium symporters (NSS) in reuptake of neurotransmitters from the synapse into the presynaptic nerve have been shown to be complemented by their involvement, together with non-plasma membrane neurotransmitter transporters, in the reverse transport of substrate (efflux) in response to psychostimulants. Recent experimental evidence implicates highly anionic phosphatidylinositol 4,5-biphosphate (PIP(2)) lipids in such functions of the serotonin (SERT) and dopamine (DAT) transporters. Thus, for both SERT and DAT, neurotransmitter efflux has been shown to be strongly regulated by the presence of PIP(2) lipids in the plasma membrane, and the electrostatic interaction of the N-terminal region of DAT with the negatively charged PIP(2) lipids. We examine the experimentally established phenotypes in a structural context obtained from computational modeling based on recent crystallographic data. The results are shown to set the stage for a mechanistic understanding of physiological actions of neurotransmitter transporters in the NSS family of membrane proteins. This article is part of a Special Issue entitled: Lipid-protein interactions.
Collapse
|
53
|
Li J, Wen PC, Moradi M, Tajkhorshid E. Computational characterization of structural dynamics underlying function in active membrane transporters. Curr Opin Struct Biol 2015; 31:96-105. [PMID: 25913536 PMCID: PMC4476910 DOI: 10.1016/j.sbi.2015.04.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Revised: 04/06/2015] [Accepted: 04/07/2015] [Indexed: 11/21/2022]
Abstract
Active transport of materials across the cellular membrane is one the most fundamental processes in biology. In order to accomplish this task, membrane transporters rely on a wide range of conformational changes spanning multiple time and size scales. These molecular events govern key functional aspects in membrane transporters, namely, coordinated gating motions underlying the alternating access mode of operation, and coupling of uphill transport of substrate to various sources of energy, for example, transmembrane electrochemical gradients and ATP binding and hydrolysis. Computational techniques such as molecular dynamics simulations and free energy calculations have equipped us with a powerful repertoire of biophysical tools offering unparalleled spatial and temporal resolutions that can effectively complement experimental methodologies, and therefore help fill the gap of knowledge in understanding the molecular basis of function in membrane transporters.
Collapse
Affiliation(s)
- Jing Li
- Department of Biochemistry, Center for Biophysics and Computational Biology, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Po-Chao Wen
- Department of Biochemistry, Center for Biophysics and Computational Biology, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Mahmoud Moradi
- Department of Biochemistry, Center for Biophysics and Computational Biology, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Emad Tajkhorshid
- Department of Biochemistry, Center for Biophysics and Computational Biology, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
| |
Collapse
|