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Vulin M, Zhong Y, Maloney BJ, Bauer B, Hartz AMS. Proteasome inhibition protects blood-brain barrier P-glycoprotein and lowers Aβ brain levels in an Alzheimer's disease model. Fluids Barriers CNS 2023; 20:70. [PMID: 37803468 PMCID: PMC10559617 DOI: 10.1186/s12987-023-00470-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 09/23/2023] [Indexed: 10/08/2023] Open
Abstract
BACKGROUND Loss of P-glycoprotein (P-gp) at the blood-brain barrier contributes to amyloid-β (Aβ) brain accumulation in Alzheimer's disease (AD). Using transgenic human amyloid precursor protein (hAPP)-overexpressing mice (Tg2576), we previously showed that Aβ triggers P-gp loss by activating the ubiquitin-proteasome pathway, which leads to P-gp degradation. Furthermore, we showed that inhibiting the ubiquitin-activating enzyme (E1) prevents P-gp loss and lowers Aβ accumulation in the brain of hAPP mice. Based on these data, we hypothesized that repurposing the FDA-approved proteasome inhibitor, bortezomib (Velcade®; BTZ), protects blood-brain barrier P-gp from degradation in hAPP mice in vivo. METHODS We treated hAPP mice with the proteasome inhibitor BTZ or a combination of BTZ with the P-gp inhibitor cyclosporin A (CSA) for 2 weeks. Vehicle-treated wild-type (WT) mice were used as a reference for normal P-gp protein expression and transport activity. In addition, we used the opioid receptor agonist loperamide as a P-gp substrate in tail flick assays to indirectly assess P-gp transport activity at the blood-brain barrier in vivo. We also determined P-gp protein expression by Western blotting, measured P-gp transport activity levels in isolated brain capillaries with live cell confocal imaging and assessed Aβ plasma and brain levels with ELISA. RESULTS We found that 2-week BTZ treatment of hAPP mice restored P-gp protein expression and transport activity in brain capillaries to levels found in WT mice. We also observed that hAPP mice displayed significant loperamide-induced central antinociception compared to WT mice indicating impaired P-gp transport activity at the blood-brain barrier of hAPP mice in vivo. Furthermore, BTZ treatment prevented loperamide-induced antinociception suggesting BTZ protected P-gp loss in hAPP mice. Further, BTZ-treated hAPP mice had lower Aβ40 and Aβ42 brain levels compared to vehicle-treated hAPP mice. CONCLUSIONS Our data indicate that BTZ protects P-gp from proteasomal degradation in hAPP mice, which helps to reduce Aβ brain levels. Our data suggest that the proteasome system could be exploited for a novel therapeutic strategy in AD, particularly since increasing Aβ transport across the blood-brain barrier may prove an effective treatment for patients.
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Affiliation(s)
- Milica Vulin
- Sanders-Brown Center On Aging, University of Kentucky, Lexington, KY, USA
| | - Yu Zhong
- Sanders-Brown Center On Aging, University of Kentucky, Lexington, KY, USA
| | - Bryan J Maloney
- Sanders-Brown Center On Aging, University of Kentucky, Lexington, KY, USA
| | - Björn Bauer
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, USA
| | - Anika M S Hartz
- Sanders-Brown Center On Aging, University of Kentucky, Lexington, KY, USA.
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, 124 Healthy Kentucky Research Building 760 Press Avenue, Lexington, KY, 40508, USA.
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2
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Schulz JA, Hartz AMS, Bauer B. ABCB1 and ABCG2 Regulation at the Blood-Brain Barrier: Potential New Targets to Improve Brain Drug Delivery. Pharmacol Rev 2023; 75:815-853. [PMID: 36973040 PMCID: PMC10441638 DOI: 10.1124/pharmrev.120.000025] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 03/10/2023] [Accepted: 03/10/2023] [Indexed: 03/29/2023] Open
Abstract
The drug efflux transporters ABCB1 and ABCG2 at the blood-brain barrier limit the delivery of drugs into the brain. Strategies to overcome ABCB1/ABCG2 have been largely unsuccessful, which poses a tremendous clinical problem to successfully treat central nervous system (CNS) diseases. Understanding basic transporter biology, including intracellular regulation mechanisms that control these transporters, is critical to solving this clinical problem.In this comprehensive review, we summarize current knowledge on signaling pathways that regulate ABCB1/ABCG2 at the blood-brain barrier. In Section I, we give a historical overview on blood-brain barrier research and introduce the role that ABCB1 and ABCG2 play in this context. In Section II, we summarize the most important strategies that have been tested to overcome the ABCB1/ABCG2 efflux system at the blood-brain barrier. In Section III, the main component of this review, we provide detailed information on the signaling pathways that have been identified to control ABCB1/ABCG2 at the blood-brain barrier and their potential clinical relevance. This is followed by Section IV, where we explain the clinical implications of ABCB1/ABCG2 regulation in the context of CNS disease. Lastly, in Section V, we conclude by highlighting examples of how transporter regulation could be targeted for therapeutic purposes in the clinic. SIGNIFICANCE STATEMENT: The ABCB1/ABCG2 drug efflux system at the blood-brain barrier poses a significant problem to successful drug delivery to the brain. The article reviews signaling pathways that regulate blood-brain barrier ABCB1/ABCG2 and could potentially be targeted for therapeutic purposes.
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Affiliation(s)
- Julia A Schulz
- Department of Pharmaceutical Sciences, College of Pharmacy (J.A.S., B.B.), Sanders-Brown Center on Aging and Department of Pharmacology and Nutritional Sciences, College of Medicine (A.M.S.H.), University of Kentucky, Lexington, Kentucky
| | - Anika M S Hartz
- Department of Pharmaceutical Sciences, College of Pharmacy (J.A.S., B.B.), Sanders-Brown Center on Aging and Department of Pharmacology and Nutritional Sciences, College of Medicine (A.M.S.H.), University of Kentucky, Lexington, Kentucky
| | - Björn Bauer
- Department of Pharmaceutical Sciences, College of Pharmacy (J.A.S., B.B.), Sanders-Brown Center on Aging and Department of Pharmacology and Nutritional Sciences, College of Medicine (A.M.S.H.), University of Kentucky, Lexington, Kentucky
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3
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Rottet S, Iqbal S, Xifaras R, Singer MT, Scott C, Deplazes E, Callaghan R. Biochemical interactions between the Atm1-like transporter from Novosphingobium aromaticivorans and heavy metals. Arch Biochem Biophys 2023:109696. [PMID: 37481198 DOI: 10.1016/j.abb.2023.109696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 06/23/2023] [Accepted: 07/19/2023] [Indexed: 07/24/2023]
Abstract
Novosphingobium aromaticivorans has the ability to survive in harsh environments by virtue of its suite of iron-containing oxygenases that biodegrade an astonishing array of aromatic compounds. It is also resistant to heavy metals through Atm1, an ATP-binding cassette protein that mediates active efflux of heavy metals conjugated to glutathione. However, Atm1 orthologues in higher organisms have been implicated in the intracellular transport of organic iron complexes. Our hypothesis suggests that the ability of Atm1 to remove heavy metals is related to the need for regulated iron handling in N. aromaticivorans to support high oxygenase activity. Here we provide the first data demonstrating a direct interaction between an iron-porphyrin compound (hemin) and NaAtm1. Hemin displayed considerably higher binding affinity and lower EC50 to stimulate ATP hydrolysis by Atm1 than Ag-GSH, GSSG or GSH, established substrates of the transporter. Co-incubation of NaAtm1, hemin with Ag-GSH in ATPase assays revealed a non-competitive interaction, indicating distinct binding sites on NaAtm1 and this property was reinforced using molecular docking analysis. Our data suggests that NaAtm1 has considerable versatility in transporting organic conjugates of metals and that this versatility enables it to play roles in detoxification processes for toxic metals and in homeostasis of iron. The ability to play these distinct roles is enabled by the plasticity of the substrate binding site within the central cavity of NaAtm1.
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Affiliation(s)
- Sarah Rottet
- CSIRO Synthetic Biology Future Science Platform, GPO Box 1700, Acton, Canberra, ACT, 2601, Australia
| | - Shagufta Iqbal
- Research School of Biology, Australian National University, Canberra, ACT, 2601, Australia
| | - Rachel Xifaras
- Research School of Biology, Australian National University, Canberra, ACT, 2601, Australia
| | - Michael T Singer
- CSIRO Synthetic Biology Future Science Platform, GPO Box 1700, Acton, Canberra, ACT, 2601, Australia
| | - Colin Scott
- CSIRO Synthetic Biology Future Science Platform, GPO Box 1700, Acton, Canberra, ACT, 2601, Australia
| | - Evelyne Deplazes
- School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Australia
| | - Richard Callaghan
- Research School of Biology, Australian National University, Canberra, ACT, 2601, Australia; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, United Kingdom.
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Badiee SA, Isu UH, Khodadadi E, Moradi M. The Alternating Access Mechanism in Mammalian Multidrug Resistance Transporters and Their Bacterial Homologs. MEMBRANES 2023; 13:568. [PMID: 37367772 PMCID: PMC10305233 DOI: 10.3390/membranes13060568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Revised: 05/23/2023] [Accepted: 05/27/2023] [Indexed: 06/28/2023]
Abstract
Multidrug resistance (MDR) proteins belonging to the ATP-Binding Cassette (ABC) transporter group play a crucial role in the export of cytotoxic drugs across cell membranes. These proteins are particularly fascinating due to their ability to confer drug resistance, which subsequently leads to the failure of therapeutic interventions and hinders successful treatments. One key mechanism by which multidrug resistance (MDR) proteins carry out their transport function is through alternating access. This mechanism involves intricate conformational changes that enable the binding and transport of substrates across cellular membranes. In this extensive review, we provide an overview of ABC transporters, including their classifications and structural similarities. We focus specifically on well-known mammalian multidrug resistance proteins such as MRP1 and Pgp (MDR1), as well as bacterial counterparts such as Sav1866 and lipid flippase MsbA. By exploring the structural and functional features of these MDR proteins, we shed light on the roles of their nucleotide-binding domains (NBDs) and transmembrane domains (TMDs) in the transport process. Notably, while the structures of NBDs in prokaryotic ABC proteins, such as Sav1866, MsbA, and mammalian Pgp, are identical, MRP1 exhibits distinct characteristics in its NBDs. Our review also emphasizes the importance of two ATP molecules for the formation of an interface between the two binding sites of NBD domains across all these transporters. ATP hydrolysis occurs following substrate transport and is vital for recycling the transporters in subsequent cycles of substrate transportation. Specifically, among the studied transporters, only NBD2 in MRP1 possesses the ability to hydrolyze ATP, while both NBDs of Pgp, Sav1866, and MsbA are capable of carrying out this reaction. Furthermore, we highlight recent advancements in the study of MDR proteins and the alternating access mechanism. We discuss the experimental and computational approaches utilized to investigate the structure and dynamics of MDR proteins, providing valuable insights into their conformational changes and substrate transport. This review not only contributes to an enhanced understanding of multidrug resistance proteins but also holds immense potential for guiding future research and facilitating the development of effective strategies to overcome multidrug resistance, thus improving therapeutic interventions.
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Affiliation(s)
| | | | | | - Mahmoud Moradi
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA; (S.A.B.); (U.H.I.); (E.K.)
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The Ubiquitin E3 Ligase Nedd4 Regulates the Expression and Amyloid-β Peptide Export Activity of P-Glycoprotein. Int J Mol Sci 2022; 23:ijms23031019. [PMID: 35162941 PMCID: PMC8834788 DOI: 10.3390/ijms23031019] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/12/2022] [Accepted: 01/16/2022] [Indexed: 02/04/2023] Open
Abstract
The ATP-binding cassette transporter, P-glycoprotein (P-gp), has been demonstrated to facilitate the clearance of amyloid-beta (Aβ) peptides, exporting the neurotoxic entity out of neurons and out of the brain via the blood–brain barrier. However, its expression and function diminish with age and in Alzheimer’s disease. P-gp is known to undergo ubiquitination, a post-translational modification that results in internalisation and/or degradation of the protein. NEDD4-1 is a ubiquitin E3 ligase that has previously been shown to ubiquitinate P-gp and reduce its cell surface expression. However, whether this effect translates into altered P-gp activity remains to be determined. siRNA was used to knockdown the expression of Nedd4 in CHO-APP cells. Western blot analysis confirmed that absence of Nedd4 was associated with increased P-gp protein expression. This was accompanied by increased transport activity, as shown by export of the P-gp substrate calcein-AM, as well as enhanced secretion of Aβ peptides, as shown by ELISA. These results implicate Nedd4 in the regulation of P-gp, and highlight a potential approach for restoring or augmenting P-gp expression and function to facilitate Aβ clearance from the brain.
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Hamdoun A, Hellmich UA, Szakacs G, Kuchler K. The incredible diversity of structures and functions of ABC transporters. FEBS Lett 2021; 595:671-674. [PMID: 33754351 DOI: 10.1002/1873-3468.14061] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Amro Hamdoun
- Scripps Institution of Oceanography, UC San Diego, CA, USA
| | - Ute A Hellmich
- Institute of Organic Chemistry and Macromolecular Chemistry, Cluster of Excellence 'Balance of the Microverse', Friedrich-Schiller-University Jena, Germany
| | - Gergely Szakacs
- Institute of Enzymology, Research Centre of Natural Sciences, Eötvös Loránd Research Network, Budapest, Hungary.,Institute of Cancer Research, Medical University of Vienna, Austria
| | - Karl Kuchler
- Max F. Perutz Laboratories, Department of Medical Biochemistry, Medical University Vienna, Austria
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McCormick JW, Ammerman L, Chen G, Vogel PD, Wise JG. Transport of Alzheimer's associated amyloid-β catalyzed by P-glycoprotein. PLoS One 2021; 16:e0250371. [PMID: 33901197 PMCID: PMC8075256 DOI: 10.1371/journal.pone.0250371] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 04/06/2021] [Indexed: 12/24/2022] Open
Abstract
P-glycoprotein (P-gp) is a critical membrane transporter in the blood brain barrier (BBB) and is implicated in Alzheimer’s disease (AD). However, previous studies on the ability of P-gp to directly transport the Alzheimer’s associated amyloid-β (Aβ) protein have produced contradictory results. Here we use molecular dynamics (MD) simulations, transport substrate accumulation studies in cell culture, and biochemical activity assays to show that P-gp actively transports Aβ. We observed transport of Aβ40 and Aβ42 monomers by P-gp in explicit MD simulations of a putative catalytic cycle. In in vitro assays with P-gp overexpressing cells, we observed enhanced accumulation of fluorescently labeled Aβ42 in the presence of Tariquidar, a potent P-gp inhibitor. We also showed that Aβ42 stimulated the ATP hydrolysis activity of isolated P-gp in nanodiscs. Our findings expand the substrate profile of P-gp, and suggest that P-gp may contribute to the onset and progression of AD.
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Affiliation(s)
- James W. McCormick
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas, United States of America
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- * E-mail: (JGW); (JWM)
| | - Lauren Ammerman
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas, United States of America
- The Center for Drug Discovery, Design and Delivery, Southern Methodist University, Dallas, Texas, United States of America
- The Center for Scientific Computation, Southern Methodist University, Dallas, Texas, United States of America
| | - Gang Chen
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas, United States of America
- The Center for Drug Discovery, Design and Delivery, Southern Methodist University, Dallas, Texas, United States of America
| | - Pia D. Vogel
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas, United States of America
- The Center for Drug Discovery, Design and Delivery, Southern Methodist University, Dallas, Texas, United States of America
| | - John G. Wise
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas, United States of America
- The Center for Drug Discovery, Design and Delivery, Southern Methodist University, Dallas, Texas, United States of America
- The Center for Scientific Computation, Southern Methodist University, Dallas, Texas, United States of America
- * E-mail: (JGW); (JWM)
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8
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Ding Y, Zhong Y, Baldeshwiler A, Abner EL, Bauer B, Hartz AMS. Protecting P-glycoprotein at the blood-brain barrier from degradation in an Alzheimer's disease mouse model. Fluids Barriers CNS 2021; 18:10. [PMID: 33676539 PMCID: PMC7937299 DOI: 10.1186/s12987-021-00245-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2020] [Accepted: 02/25/2021] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND Failure to clear Aβ from the brain is partly responsible for Aβ brain accumulation in Alzheimer's disease (AD). A critical protein for clearing Aβ across the blood-brain barrier is the efflux transporter P-glycoprotein (P-gp). In AD, P-gp levels are reduced, which contributes to impaired Aβ brain clearance. However, the mechanism responsible for decreased P-gp levels is poorly understood and there are no strategies available to protect P-gp. We previously demonstrated in isolated brain capillaries ex vivo that human Aβ40 (hAβ40) triggers P-gp degradation by activating the ubiquitin-proteasome pathway. In this pathway, hAβ40 initiates P-gp ubiquitination, leading to internalization and proteasomal degradation of P-gp, which then results in decreased P-gp protein expression and transport activity levels. Here, we extend this line of research and present results from an in vivo study using a transgenic mouse model of AD (human amyloid precursor protein (hAPP)-overexpressing mice; Tg2576). METHODS In our study, hAPP mice were treated with vehicle, nocodazole (NCZ, microtubule inhibitor to block P-gp internalization), or a combination of NCZ and the P-gp inhibitor cyclosporin A (CSA). We determined P-gp protein expression and transport activity levels in isolated mouse brain capillaries and Aβ levels in plasma and brain tissue. RESULTS Treating hAPP mice with 5 mg/kg NCZ for 14 days increased P-gp levels to levels found in WT mice. Consistent with this, P-gp-mediated hAβ42 transport in brain capillaries was increased in NCZ-treated hAPP mice compared to untreated hAPP mice. Importantly, NCZ treatment significantly lowered hAβ40 and hAβ42 brain levels in hAPP mice, whereas hAβ40 and hAβ42 levels in plasma remained unchanged. CONCLUSIONS These findings provide in vivo evidence that microtubule inhibition maintains P-gp protein expression and transport activity levels, which in turn helps to lower hAβ brain levels in hAPP mice. Thus, protecting P-gp at the blood-brain barrier may provide a novel therapeutic strategy for AD and other Aβ-based pathologies.
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Affiliation(s)
- Yujie Ding
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, 40536, USA
| | - Yu Zhong
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, 40536, USA
| | - Andrea Baldeshwiler
- Department of Pharmacy Practice and Pharmaceutical Sciences, College of Pharmacy, University of Minnesota, Duluth, Minnesota, 55812, USA
| | - Erin L Abner
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, 40536, USA
- Department of Epidemiology, College of Public Health, University of Kentucky, Lexington, KY, 40536, USA
| | - Björn Bauer
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, 40536, USA
| | - Anika M S Hartz
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, 40536, USA.
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, 40536, USA.
- University of Kentucky Sanders-Brown Center on Aging, 800 S Limestone, Lexington, KY, 40536, USA.
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New Evidence for P-gp-Mediated Export of Amyloid-β PEPTIDES in Molecular, Blood-Brain Barrier and Neuronal Models. Int J Mol Sci 2020; 22:ijms22010246. [PMID: 33383667 PMCID: PMC7795149 DOI: 10.3390/ijms22010246] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 12/23/2020] [Accepted: 12/25/2020] [Indexed: 12/17/2022] Open
Abstract
Defective clearance mechanisms lead to the accumulation of amyloid-beta (Aβ) peptides in the Alzheimer’s brain. Though predominantly generated in neurons, little is known about how these hydrophobic, aggregation-prone, and tightly membrane-associated peptides exit into the extracellular space where they deposit and propagate neurotoxicity. The ability for P-glycoprotein (P-gp), an ATP-binding cassette (ABC) transporter, to export Aβ across the blood-brain barrier (BBB) has previously been reported. However, controversies surrounding the P-gp–Aβ interaction persist. Here, molecular data affirm that both Aβ40 and Aβ42 peptide isoforms directly interact with and are substrates of P-gp. This was reinforced ex vivo by the inhibition of Aβ42 transport in brain capillaries from P-gp-knockout mice. Moreover, we explored whether P-gp could exert the same role in neurons. Comparison between non-neuronal CHO-APP and human neuroblastoma SK-N-SH cells revealed that P-gp is expressed and active in both cell types. Inhibiting P-gp activity using verapamil and nicardipine impaired Aβ40 and Aβ42 secretion from both cell types, as determined by ELISA. Collectively, these findings implicate P-gp in Aβ export from neurons, as well as across the BBB endothelium, and suggest that restoring or enhancing P-gp function could be a viable therapeutic approach for removing excess Aβ out of the brain in Alzheimer’s disease.
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