1
|
Vecchio FL, Bisceglia P, Imbimbo BP, Lozupone M, Latino RR, Resta E, Leone M, Solfrizzi V, Greco A, Daniele A, Watling M, Panza F, Seripa D. Are apolipoprotein E fragments a promising new therapeutic target for Alzheimer’s disease? Ther Adv Chronic Dis 2022; 13:20406223221081605. [PMID: 35321401 PMCID: PMC8935560 DOI: 10.1177/20406223221081605] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 01/28/2022] [Indexed: 11/17/2022] Open
Abstract
Human apolipoprotein E (ApoE) is a 299-amino acid secreted glycoprotein that binds cholesterol and phospholipids. ApoE exists as three common isoforms (ApoE2, ApoE3, and ApoE4) and heterozygous carriers of the ε4 allele of the gene encoding ApoE (APOE) have a fourfold greater risk of developing Alzheimer’s disease (AD). The enzymes thrombin, cathepsin D, α-chymotrypsin-like serine protease, and high-temperature requirement serine protease A1 are responsible for ApoE proteolytic processing resulting in bioactive C-terminal-truncated fragments that vary depending on ApoE isoforms, brain region, aging, and neural injury. The objectives of the present narrative review were to describe ApoE processing, discussing current hypotheses about the potential role of various ApoE fragments in AD pathophysiology, and reviewing the current development status of different anti-ApoE drugs. The exact mechanism by which APOE gene variants increase/decrease AD risk and the role of ApoE fragments in the deposition are not fully understood, but APOE is known to directly affect tau-mediated neurodegeneration. ApoE fragments co-localize with neurofibrillary tangles and amyloid β (Aβ) plaques, and may cause neurodegeneration. Among anti-ApoE approaches, a fascinating strategy may be to therapeutically overexpress ApoE2 in APOE ε4/ε4 carriers through vector administration or liposomal delivery systems. Another approach involves reducing ApoE4 expression by intracerebroventricular antisense oligonucleotides that significantly decreased Aβ pathology in transgenic mice. Differences in the proteolytic processing of distinct ApoE isoforms and the use of ApoE fragments as mimetic peptides in AD treatment are also under investigation. Treatment with peptides that mimic the structural and biological properties of native ApoE may reduce Aβ deposition, tau hyperphosphorylation, and glial activation in mouse models of Aβ pathology. Alternative strategies involve the use of ApoE4 structure correctors, passive immunization to target a certain form of ApoE, conversion of the ApoE4 aminoacid sequence into that of ApoE3 or ApoE2, and inhibition of the ApoE-Aβ interaction.
Collapse
Affiliation(s)
- Filomena Lo Vecchio
- Research Laboratory, Complex Structure of Geriatrics, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Foggia 71013, Italy
| | - Paola Bisceglia
- Research Laboratory, Complex Structure of Geriatrics, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
| | | | - Madia Lozupone
- Neurodegenerative Disease Unit, Department of Basic Medicine, Neuroscience, and Sense Organs, University of Bari Aldo Moro, Bari, Italy
| | - Raffaela Rita Latino
- Complex Structure of Neurology, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
| | - Emanuela Resta
- Translational Medicine and Management of Health Systems, University of Foggia, Foggia, Italy
| | - Maurizio Leone
- Complex Structure of Neurology, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
| | - Vincenzo Solfrizzi
- ‘Cesare Frugoni’ Internal and Geriatric Medicine and Memory Unit, University of Bari ‘Aldo Moro’, Bari, Italy
| | - Antonio Greco
- Department of Neuroscience, Catholic University of the Sacred Heart, Rome, Italy; Neurology Unit, IRCCS Fondazione Policlinico Universitario A. Gemelli, Rome, Italy
- Research Laboratory, Complex Structure of Geriatrics, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
| | | | - Mark Watling
- CNS & Pain Department, TranScrip Ltd, Reading, UK
| | - Francesco Panza
- Research Laboratory, Complex Structure of Geriatrics, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Foggia, Italy
- Population Health Unit, Healthy Aging Phenotypes Research Unit, ‘Salus in Apulia Study’, National Institute of Gastroenterology ‘Saverio de Bellis’, Research Hospital, Castellana Grotte, Bari 70013, Italy
| | - Davide Seripa
- Research Laboratory, Complex Structure of Geriatrics, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
- Hematology and Stem Cell Transplant Unit, ‘Vito Fazzi’ Hospital, Lecce, Italy
| |
Collapse
|
2
|
Xue M, Li S, Xu M, Yan L, Laskowitz DT, Kolls BJ, Chen G, Qian X, Wang Y, Song H, Wang Y. Antagonism of nicotinic acetycholinergic receptors by CN‐105, an apoE‐mimetic peptide reduces stroke‐induced excitotoxicity. Clin Transl Med 2022; 12:e677. [PMID: 35075820 PMCID: PMC8787096 DOI: 10.1002/ctm2.677] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 11/21/2021] [Accepted: 11/25/2021] [Indexed: 12/19/2022] Open
Affiliation(s)
- Miaomiao Xue
- State Key Laboratory of Proteomics Beijing Proteome Research Center National Center for Protein Sciences (Beijing) Beijing Institute of Lifeomics Beijing China
| | - Shuya Li
- Department of Neurology Beijing Tiantan Hospital Capital Medical University Beijing China
- China National Clinical Research Center for Neurological Diseases Beijing China
| | - Mingzhi Xu
- State Key Laboratory of Proteomics Beijing Proteome Research Center National Center for Protein Sciences (Beijing) Beijing Institute of Lifeomics Beijing China
| | - Li Yan
- ICE Bioscience Inc. Beijing China
| | - Daniel T. Laskowitz
- Duke Clinical Research Institute Duke University School of Medicine Durham North Carolina USA
- Department of Neurology Duke University Durham North Carolina USA
- Department of Anesthesiology Duke University Durham North Carolina USA
- Aegis‐CN, LLC Durham North Carolina USA
| | - Brad J. Kolls
- Duke Clinical Research Institute Duke University School of Medicine Durham North Carolina USA
- Department of Neurology Duke University Durham North Carolina USA
| | - Gang Chen
- Guangdong Cerebtron Biotech Ltd. Guangdong China
| | - Xiaohong Qian
- State Key Laboratory of Proteomics Beijing Proteome Research Center National Center for Protein Sciences (Beijing) Beijing Institute of Lifeomics Beijing China
| | - Yongjun Wang
- Department of Neurology Beijing Tiantan Hospital Capital Medical University Beijing China
- China National Clinical Research Center for Neurological Diseases Beijing China
| | - Haifeng Song
- State Key Laboratory of Proteomics Beijing Proteome Research Center National Center for Protein Sciences (Beijing) Beijing Institute of Lifeomics Beijing China
| | - Yi Wang
- State Key Laboratory of Proteomics Beijing Proteome Research Center National Center for Protein Sciences (Beijing) Beijing Institute of Lifeomics Beijing China
| |
Collapse
|
3
|
Understanding the Role of ApoE Fragments in Alzheimer's Disease. Neurochem Res 2018; 44:1297-1305. [PMID: 30225748 DOI: 10.1007/s11064-018-2629-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 08/23/2018] [Accepted: 09/04/2018] [Indexed: 01/05/2023]
Abstract
Alzheimer's disease (AD) is one of the most devastating neurodegenerative diseases. It has been known for decades that the APOE ɛ4 allele is the most significant genetic risk factor for late-onset AD and yet its precise role in the disease remains unclear. The APOE gene encodes apolipoprotein E (apoE), a 35 kDa glycoprotein highly expressed in the brain. There are three different isoforms: apoE3 is the most common allele in the population, whilst apoE2 decreases, and apoE4 increases AD risk. ApoE has numerous functions that affect neuronal and non-neuronal cells, thus how it contributes to disease onset and progression is hotly debated. The apoE4 isoform has been linked to the accumulation of both of the major pathological hallmarks of AD, amyloid plaques containing amyloid β peptides, and neurofibrillary tangles containing hyperphosphorylated tau protein, as well as other hallmarks of the disease, including inflammation and oxidative stress. Numerous studies have shown that apoE undergoes fragmentation in the human brain, and that the fragmentation pattern varies between isoforms. It was previously shown that apoE4 has neurotoxic functions, however recent data has also identified a neuroprotective role for the apoE N-terminal 25 kDa fragment, which is more prevalent in apoE3 individuals. The ability of the apoE 25 kDa fragment to promote neurite outgrowth was recently demonstrated and this suggests there is a potential loss of neuroprotection in apoE4 individuals in addition to the previously described gain of toxic function for specific apoE4 fragments. Here we review the enzymes proposed to be responsible for apoE fragmentation, the specific functions of different apoE fragments and their possible links with AD.
Collapse
|
4
|
Muñoz SS, Li H, Ruberu K, Chu Q, Saghatelian A, Ooi L, Garner B. The serine protease HtrA1 contributes to the formation of an extracellular 25-kDa apolipoprotein E fragment that stimulates neuritogenesis. J Biol Chem 2018; 293:4071-4084. [PMID: 29414786 PMCID: PMC5857987 DOI: 10.1074/jbc.ra117.001278] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 01/24/2018] [Indexed: 12/31/2022] Open
Abstract
Apolipoprotein-E (apoE) is a glycoprotein highly expressed in the brain, where it appears to play a role in lipid transport, β-amyloid clearance, and neuronal signaling. ApoE proteolytic fragments are also present in the brain, but the enzymes responsible for apoE fragmentation are unknown, and the biological activity of specific apoE fragments remains to be determined. Here we utilized SK-N-SH neuroblastoma cells differentiated into neurons with all-trans-retinoic acid (ATRA) to study extracellular apoE proteolysis. ApoE fragments were detectable in culture supernatants after 3 days, and their levels were increased for up to 9 days in the presence of ATRA. The concentration of apoE fragments was positively correlated with levels of the neuronal maturation markers (PSD95 and SMI32). The most abundant apoE fragments were 25- and 28-kDa N-terminal fragments that both contained sialylated glycosylation and bound to heparin. We detected apoE fragments only in the extracellular milieu and not in cell lysates, suggesting that an extracellular protease contributes to apoE fragmentation. Of note, siRNA-mediated knockdown of high-temperature requirement serine peptidase A1 (HtrA1) and a specific HtrA1 inhibitor reduced apoE 25-kDa fragment formation by 41 and 86%, respectively. Recombinant 25-kDa fragment apoE and full-length apoE both stimulated neuritogenesis in vitro, increasing neuroblastoma neurite growth by more than 2-fold over a 6-day period. This study provides a cellular model for assessing apoE proteolysis, indicates that HtrA1 regulates apoE 25-kDa fragment formation under physiological conditions, and reveals a new neurotrophic function for the apoE 25-kDa fragment.
Collapse
Affiliation(s)
- Sonia Sanz Muñoz
- From the Illawarra Health and Medical Research Institute and
- the School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia and
| | - Hongyun Li
- From the Illawarra Health and Medical Research Institute and
- the School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia and
| | - Kalani Ruberu
- From the Illawarra Health and Medical Research Institute and
- the School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia and
| | - Qian Chu
- the Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, California 92037
| | - Alan Saghatelian
- the Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, California 92037
| | - Lezanne Ooi
- From the Illawarra Health and Medical Research Institute and
- the School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia and
| | - Brett Garner
- From the Illawarra Health and Medical Research Institute and
- the School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia and
| |
Collapse
|
5
|
Wang HY, Trocmé-Thibierge C, Stucky A, Shah SM, Kvasic J, Khan A, Morain P, Guignot I, Bouguen E, Deschet K, Pueyo M, Mocaer E, Ousset PJ, Vellas B, Kiyasova V. Increased Aβ 42-α7-like nicotinic acetylcholine receptor complex level in lymphocytes is associated with apolipoprotein E4-driven Alzheimer's disease pathogenesis. ALZHEIMERS RESEARCH & THERAPY 2017; 9:54. [PMID: 28750690 PMCID: PMC5530996 DOI: 10.1186/s13195-017-0280-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 06/21/2017] [Indexed: 12/19/2022]
Abstract
BACKGROUND The apolipoprotein E ε4 (APOE4) genotype is a prominent late-onset Alzheimer's disease (AD) risk factor. ApoE4 disrupts memory function in rodents and may contribute to both plaque and tangle formation. METHODS Coimmunoprecipitation and Western blot detection were used to determine: 1) the effects of select fragments from the apoE low-density lipoprotein (LDL) binding domain and recombinant apoE subtypes on amyloid beta (Aβ)42-α7 nicotinic acetylcholine receptor (α7nAChR) interaction and tau phosphorylation in rodent brain synaptosomes; and 2) the level of Aβ42-α7nAChR complexes in matched controls and patients with mild cognitive impairment (MCI) and dementia due to AD with known APOE genotypes. RESULTS In an ex vivo study using rodent synaptosomes, apoE141-148 of the apoE promotes Aβ42-α7nAChR association and Aβ42-induced α7nAChR-dependent tau phosphorylation. In a single-blind study, we examined lymphocytes isolated from control subjects, patients with MCI and dementia due to AD with known APOE genotypes, sampled at two time points (1 year apart). APOE ε4 genotype was closely correlated with heightened Aβ42-α7nAChR complex levels and with blunted exogenous Aβ42 effects in lymphocytes derived from AD and MCI due to AD cases. Similarly, plasma from APOE ε4 carriers enhanced the Aβ42-induced Aβ42-α7nAChR association in rat cortical synaptosomes. The progression of cognitive decline in APOE ε4 carriers correlated with higher levels of Aβ42-α7nAChR complexes in lymphocytes and greater enhancement by their plasma of Aβ42-induced Aβ42-α7nAChR association in rat cortical synaptosomes. CONCLUSIONS Our data suggest that increased lymphocyte Aβ42-α7nAChR-like complexes may indicate the presence of AD pathology especially in APOE ε4 carriers. We show that apoE, especially apoE4, promotes Aβ42-α7nAChR interaction and Aβ42-induced α7nAChR-dependent tau phosphorylation via its apoE141-148 domain. These apoE-mediated effects may contribute to the APOE ε4-driven neurodysfunction and AD pathologies.
Collapse
Affiliation(s)
- Hoau-Yan Wang
- Department of Physiology, Pharmacology and Neuroscience, CUNY School of Medicine, 160 Convent Avenue, New York, NY, 10031, USA. .,Department of Physiology, Pharmacology & Neuroscience, The City University of New York School of Medicine, CDI-3370 85 St. Nicholas Terrace, New York, NY, 10027, USA.
| | | | - Andres Stucky
- Department of Physiology, Pharmacology and Neuroscience, CUNY School of Medicine, 160 Convent Avenue, New York, NY, 10031, USA.,Department of Biology, Neuroscience Program, Graduate School of The City University of New York, New York, New York, 10061, USA
| | - Sanket M Shah
- Department of Physiology, Pharmacology and Neuroscience, CUNY School of Medicine, 160 Convent Avenue, New York, NY, 10031, USA
| | - Jessica Kvasic
- Department of Physiology, Pharmacology and Neuroscience, CUNY School of Medicine, 160 Convent Avenue, New York, NY, 10031, USA
| | - Amber Khan
- Department of Physiology, Pharmacology and Neuroscience, CUNY School of Medicine, 160 Convent Avenue, New York, NY, 10031, USA
| | - Philippe Morain
- Institut de Recherches Internationales Servier, 50 Rue Carnot, 92284, Suresnes, France
| | - Isabelle Guignot
- Institut de Recherches Internationales Servier, 50 Rue Carnot, 92284, Suresnes, France
| | - Eva Bouguen
- Institut de Recherches Internationales Servier, 50 Rue Carnot, 92284, Suresnes, France
| | - Karine Deschet
- Institut de Recherches Internationales Servier, 50 Rue Carnot, 92284, Suresnes, France
| | - Maria Pueyo
- Institut de Recherches Internationales Servier, 50 Rue Carnot, 92284, Suresnes, France
| | - Elisabeth Mocaer
- Institut de Recherches Internationales Servier, 50 Rue Carnot, 92284, Suresnes, France
| | - Pierre-Jean Ousset
- Alzheimer's Disease Research and Clinical Center, Inserm U1027, Toulouse University Hospital, Toulouse, France
| | - Bruno Vellas
- Alzheimer's Disease Research and Clinical Center, Inserm U1027, Toulouse University Hospital, Toulouse, France
| | - Vera Kiyasova
- Institut de Recherches Internationales Servier, 50 Rue Carnot, 92284, Suresnes, France
| |
Collapse
|
6
|
Suresh A, Hung A. Molecular simulation study of the unbinding of α-conotoxin [ϒ4E]GID at the α7 and α4β2 neuronal nicotinic acetylcholine receptors. J Mol Graph Model 2016; 70:109-121. [PMID: 27721068 DOI: 10.1016/j.jmgm.2016.09.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 08/11/2016] [Accepted: 09/05/2016] [Indexed: 12/27/2022]
Abstract
The α7 and α4β2 neuronal nicotinic receptors belonging to the family of ligand-gated ion channels are most prevalent in the brain, and are implicated in various neurodegenerative disorders. α-conotoxin GID (and its analogue [ϒ4E]GID) specifically inhibits these subtypes, with more affinity towards the human α7 (hα7) subtype, and is valuable in understanding the physiological roles of these receptors. In this study, we use umbrella-sampling molecular dynamics simulations to understand the mechanism of interaction between [ϒ4E]GID and the agonist binding pockets of the α4β2 and the hα7 receptors, and to estimate their relative binding affinities (ΔGbind). The obtained ΔGbind values indicate stronger interaction with the hα7 receptor, in agreement with previous experimental studies. Simulations also revealed different unbinding pathways between the two receptor subtypes, enabling identification of a number of interactions at locations far from the orthosteric binding site which may explain the difference in [ϒ4E]GID potency. The pathways identified will help in the design of novel conotoxins with increased potency at α4β2, for which there is currently no known highly potent conotoxin inhibitor. Computational mutational free energy analyses also revealed a number of possible single-site mutations to GID which might enhance its selective binding to α4β2 over α7.
Collapse
Affiliation(s)
- Abishek Suresh
- School of Science, RMIT University, GPO Box 2476, Melbourne, Victoria 3001, Australia
| | - Andrew Hung
- School of Science, RMIT University, GPO Box 2476, Melbourne, Victoria 3001, Australia.
| |
Collapse
|
7
|
Grishin AA, Cuny H, Hung A, Clark RJ, Brust A, Akondi K, Alewood PF, Craik DJ, Adams DJ. Identifying key amino acid residues that affect α-conotoxin AuIB inhibition of α3β4 nicotinic acetylcholine receptors. J Biol Chem 2013; 288:34428-42. [PMID: 24100032 DOI: 10.1074/jbc.m113.512582] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
α-Conotoxin AuIB is a selective α3β4 nicotinic acetylcholine receptor (nAChR) subtype inhibitor. Its analgesic properties are believed to result from it activating GABAB receptors and subsequently inhibiting CaV2.2 voltage-gated calcium channels. The structural determinants that mediate diverging AuIB activity at these targets are unknown. We performed alanine scanning mutagenesis of AuIB and α3β4 nAChR, homology modeling, and molecular dynamics simulations to identify the structural determinants of the AuIB·α3β4 nAChR interaction. Two alanine-substituted AuIB analogues, [P6A]AuIB and [F9A]AuIB, did not inhibit the α3β4 nAChR. NMR and CD spectroscopy studies demonstrated that [F9A]AuIB retains its native globular structure, so its activity loss is probably due to loss of specific toxin-receptor residue pairwise contacts. Compared with AuIB, the concentration-response curve for inhibition of α3β4 by [F9A]AuIB shifted rightward more than 10-fold, and its subtype selectivity profile changed. Homology modeling and molecular dynamics simulations suggest that Phe-9 of AuIB interacts with a two-residue binding pocket on the β4 nAChR subunit. This hypothesis was confirmed by site-directed mutagenesis of the β4-Trp-59 and β4-Lys-61 residues of loop D, which form a putative binding pocket. AuIB analogues with Phe-9 substitutions corroborated the finding of a binding pocket on the β4 subunit and gave further insight into how AuIB Phe-9 interacts with the β4 subunit. In summary, we identified critical residues that mediate interactions between AuIB and its cognate nAChR subtype. These findings might help improve the design of analgesic conopeptides that selectively "avoid" nAChR receptors while targeting receptors involved with nociception.
Collapse
Affiliation(s)
- Anton A Grishin
- From the Health Innovations Research Institute, RMIT University, Melbourne, Victoria 3083, Australia and
| | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Yakel JL. Cholinergic receptors: functional role of nicotinic ACh receptors in brain circuits and disease. Pflugers Arch 2013; 465:441-50. [PMID: 23307081 PMCID: PMC3633680 DOI: 10.1007/s00424-012-1200-1] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 12/03/2012] [Accepted: 12/03/2012] [Indexed: 12/13/2022]
Abstract
The neurotransmitter acetylcholine (ACh) can regulate neuronal excitability throughout the nervous system by acting on both the cys-loop ligand-gated nicotinic ACh receptor channels (nAChRs) and the G protein-coupled muscarinic ACh receptors (mAChRs). The hippocampus is an important area in the brain for learning and memory, where both nAChRs and mAChRs are expressed. The primary cholinergic input to the hippocampus arises from the medial septum and diagonal band of Broca, the activation of which can activate both nAChRs and mAChRs in the hippocampus and regulate synaptic communication and induce oscillations that are thought to be important for cognitive function. Dysfunction in the hippocampal cholinergic system has been linked with cognitive deficits and a variety of neurological disorders and diseases, including Alzheimer's disease and schizophrenia. My lab has focused on the role of the nAChRs in regulating hippocampal function, from understanding the expression and functional properties of the various subtypes of nAChRs, and what role these receptors may be playing in regulating synaptic plasticity. Here, I will briefly review this work, and where we are going in our attempts to further understand the role of these receptors in learning and memory, as well as in disease and neuroprotection.
Collapse
Affiliation(s)
- Jerrel L Yakel
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, P.O. Box 12233, Mail Drop F2-08, Research Triangle Park, NC 27709, USA.
| |
Collapse
|
9
|
Rohde LAH, Ahring PK, Jensen ML, Nielsen EØ, Peters D, Helgstrand C, Krintel C, Harpsøe K, Gajhede M, Kastrup JS, Balle T. Intersubunit bridge formation governs agonist efficacy at nicotinic acetylcholine α4β2 receptors: unique role of halogen bonding revealed. J Biol Chem 2011; 287:4248-59. [PMID: 22170047 DOI: 10.1074/jbc.m111.292243] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The α4β2 subtype of the nicotinic acetylcholine receptor has been pursued as a drug target for treatment of psychiatric and neurodegenerative disorders and smoking cessation aids for decades. Still, a thorough understanding of structure-function relationships of α4β2 agonists is lacking. Using binding experiments, electrophysiology and x-ray crystallography we have investigated a consecutive series of five prototypical pyridine-containing agonists derived from 1-(pyridin-3-yl)-1,4-diazepane. A correlation between binding affinities at α4β2 and the acetylcholine-binding protein from Lymnaea stagnalis (Ls-AChBP) confirms Ls-AChBP as structural surrogate for α4β2 receptors. Crystal structures of five agonists with efficacies at α4β2 from 21-76% were determined in complex with Ls-AChBP. No variation in closure of loop C is observed despite large efficacy variations. Instead, the efficacy of a compound appears tightly coupled to its ability to form a strong intersubunit bridge linking the primary and complementary binding interfaces. For the tested agonists, a specific halogen bond was observed to play a large role in establishing such strong intersubunit anchoring.
Collapse
Affiliation(s)
- Line Aagot Hede Rohde
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Copenhagen 2100, Denmark
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Bhattacharjee PS, Huq TS, Mandal TK, Graves RA, Muniruzzaman S, Clement C, McFerrin HE, Hill JM. A novel peptide derived from human apolipoprotein E is an inhibitor of tumor growth and ocular angiogenesis. PLoS One 2011; 6:e15905. [PMID: 21253017 PMCID: PMC3017052 DOI: 10.1371/journal.pone.0015905] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 11/25/2010] [Indexed: 12/21/2022] Open
Abstract
Angiogenesis is a hallmark of tumor development and metastasis and now a validated target for cancer treatment. We previously reported that a novel dimer peptide (apoEdp) derived from the receptor binding region of human apolipoprotein E (apoE) inhibits virus-induced angiogenesis. However, its role in tumor anti-angiogenesis is unknown. This study demonstrates that apoEdp has anti-angiogenic property in vivo through reduction of tumor growth in a mouse model and ocular angiogenesis in a rabbit eye model. Our in vitro studies show that apoEdp inhibits human umbilical vein endothelial cell proliferation, migration, invasion and capillary tube formation. We document that apoEdp inhibits vascular endothelial growth factor-induced Flk-1 activation as well as downstream signaling pathways that involve c-Src, Akt, eNOS, FAK, and ERK1/2. These in vitro data suggest potential sites of the apoE dipeptide inhibition that could occur in vivo. This is the first evidence that a synthetic dimer peptide mimicking human apoE has anti-angiogenesis functions and could be an anti-tumor drug candidate.
Collapse
Affiliation(s)
- Partha S. Bhattacharjee
- Department of Biology, Xavier University of Louisiana, New Orleans, Louisiana, United States of America
- Department of Ophthalmology, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Tashfin S. Huq
- Department of Biology, Xavier University of Louisiana, New Orleans, Louisiana, United States of America
| | - Tarun K. Mandal
- College of Pharmacy, Xavier University of Louisiana, New Orleans, Louisiana, United States of America
| | - Richard A. Graves
- College of Pharmacy, Xavier University of Louisiana, New Orleans, Louisiana, United States of America
| | - Syed Muniruzzaman
- Department of Biology, Xavier University of Louisiana, New Orleans, Louisiana, United States of America
| | - Christian Clement
- Department of Ophthalmology, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Harris E. McFerrin
- Department of Biology, Xavier University of Louisiana, New Orleans, Louisiana, United States of America
| | - James M. Hill
- Department of Ophthalmology, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
- Neuroscience Center, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
- Department of Microbiology, Immunology and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
- Department of Pharmacology, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
- * E-mail:
| |
Collapse
|
11
|
Brams M, Gay EA, Sáez JC, Guskov A, van Elk R, van der Schors RC, Peigneur S, Tytgat J, Strelkov SV, Smit AB, Yakel JL, Ulens C. Crystal structures of a cysteine-modified mutant in loop D of acetylcholine-binding protein. J Biol Chem 2010; 286:4420-8. [PMID: 21115477 DOI: 10.1074/jbc.m110.188730] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Covalent modification of α7 W55C nicotinic acetylcholine receptors (nAChR) with the cysteine-modifying reagent [2-(trimethylammonium)ethyl] methanethiosulfonate (MTSET(+)) produces receptors that are unresponsive to acetylcholine, whereas methyl methanethiolsulfonate (MMTS) produces enhanced acetylcholine-gated currents. Here, we investigate structural changes that underlie the opposite effects of MTSET(+) and MMTS using acetylcholine-binding protein (AChBP), a homolog of the extracellular domain of the nAChR. Crystal structures of Y53C AChBP show that MTSET(+)-modification stabilizes loop C in an extended conformation that resembles the antagonist-bound state, which parallels our observation that MTSET(+) produces unresponsive W55C nAChRs. The MMTS-modified mutant in complex with acetylcholine is characterized by a contracted C-loop, similar to other agonist-bound complexes. Surprisingly, we find two acetylcholine molecules bound in the ligand-binding site, which might explain the potentiating effect of MMTS modification in W55C nAChRs. Unexpectedly, we observed in the MMTS-Y53C structure that ten phosphate ions arranged in two rings at adjacent sites are bound in the vestibule of AChBP. We mutated homologous residues in the vestibule of α1 GlyR and observed a reduction in the single channel conductance, suggesting a role of this site in ion permeation. Taken together, our results demonstrate that targeted modification of a conserved aromatic residue in loop D is sufficient for a conformational switch of AChBP and that a defined region in the vestibule of the extracellular domain contributes to ion conduction in anion-selective Cys-loop receptors.
Collapse
Affiliation(s)
- Marijke Brams
- Laboratory of Structural Neurobiology, KULeuven, 3000 Leuven, Belgium
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Yakel JL. Gating of nicotinic ACh receptors: latest insights into ligand binding and function. J Physiol 2009; 588:597-602. [PMID: 19917567 DOI: 10.1113/jphysiol.2009.182691] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are in the superfamily of cys-loop receptors, and are widely expressed in the nervous system where they participate in a variety of physiological functions, including regulating excitability and neurotransmitter release, as well as neuromuscular contraction. Members of the cys-loop family of receptors, which also includes the molluscan ACh-binding protein (AChBP), a soluble protein that is analogous to the extracellular ligand-binding domain of the cys-loop receptors, are pentameric assemblies of five subunits, with each subunit arranged around a central pore. The binding of ACh to the extracellular interface between two subunits induces channel opening. With the recent 4 A resolution of the Torpedo nAChR, and the crystal structure of the AChBP, much has been learned about the structure of the ligand-binding domain and the channel pore, as well as major structural rearrangements that may confer channel opening, including a major rearrangement of the C-loop within the ligand binding pocket, and perhaps other regions including the F-loop (the beta8-beta9 linker), the beta1-beta2 linker and the cys-loop. Here I will review the latest findings from my lab aimed at a further understanding of the function of the neuronal nAChR channels (and in particular the role of desensitization), and our search for novel AChBP species that may lead to a further understanding of the function of the cys-loop receptor family.
Collapse
Affiliation(s)
- Jerrel L Yakel
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, Department of Health and Human Services, PO Box 12233, Research Triangle Park, NC 27709, USA.
| |
Collapse
|
13
|
Barrantes FJ, Borroni V, Vallés S. Neuronal nicotinic acetylcholine receptor-cholesterol crosstalk in Alzheimer's disease. FEBS Lett 2009; 584:1856-63. [PMID: 19914249 DOI: 10.1016/j.febslet.2009.11.036] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Revised: 11/09/2009] [Accepted: 11/10/2009] [Indexed: 10/20/2022]
Abstract
Alzheimer's disease (AD) is one of the most devastating diseases of the central nervous system (CNS). It is characterized by two neuropathological findings: amyloid plaques and neurofibrillary tangles. AD is also accompanied by an extensive functional deficit in the cholinergic system, involving the neuronal-type nicotinic acetylcholine receptor (AChR). Furthermore there is increasing evidence showing a misregulation of cholesterol metabolism in the development of the disease. Since cholesterol affects AChR protein at multiple levels, the cognitive impairment and other neurological correlates of AD might be partly associated with an abnormal crosstalk between the receptor protein and the sterol in this synaptopathy.
Collapse
Affiliation(s)
- Francisco J Barrantes
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, UNESCO Chair of Biophysics and Molecular Neurobiology, Bahía Blanca, Argentina.
| | | | | |
Collapse
|
14
|
Crutcher KA, Lilley HN, Anthony SR, Zhou W, Narayanaswami V. Full-length apolipoprotein E protects against the neurotoxicity of an apoE-related peptide. Brain Res 2009; 1306:106-15. [PMID: 19836363 DOI: 10.1016/j.brainres.2009.10.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 10/06/2009] [Accepted: 10/08/2009] [Indexed: 11/26/2022]
Abstract
Apolipoprotein E was found to protect against the neurotoxic effects of a dimeric peptide derived from the receptor-binding region of this protein (residues 141-149). Both apoE3 and apoE4 conferred protection but the major N-terminal fragment of each isoform did not. Nor was significant protection provided by bovine serum albumin or apoA-I. Full-length apoE3 and apoE4 also inhibited the uptake of a fluorescent-labeled derivative of the peptide, suggesting that the mechanism of inhibition might involve competition for cell surface receptors/proteoglycans that mediate endocytosis and/or signaling pathways. These results might bear on the question of the role of apoE in neuronal degeneration, such as occurs in Alzheimer's disease where apoE4 confers a significantly greater risk of pathology.
Collapse
Affiliation(s)
- K A Crutcher
- Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
| | | | | | | | | |
Collapse
|
15
|
Bencherif M, Lippiello PM. Alpha7 neuronal nicotinic receptors: the missing link to understanding Alzheimer's etiopathology? Med Hypotheses 2009; 74:281-5. [PMID: 19800174 DOI: 10.1016/j.mehy.2009.09.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Accepted: 09/07/2009] [Indexed: 11/27/2022]
Abstract
Evidence supports the premise that alpha7 nicotinic acetylcholine receptors in the central nervous system, sometimes referred to as neuronal nicotinic receptors (NNRs), play a central role in the development of Alzheimer's disease (AD) pathophysiology. Moreover, these receptors may represent the key to unifying aspects of the cholinergic hypothesis of AD with many of the apparently disparate mechanisms such as beta-amyloid deposition, tau hyperphosphorylation, and ApoE4 abnormalities variously proposed to underlie the progression of the disease. We hypothesize that neuronal degeneration in incipient AD is the result of coincident events involving, at their core, deficits in alpha7 NNR function. The resulting hypocholinergic tone could potentially have serious consequences since alpha7 NNRs are known to modulate fundamental pathways involved in cell survival such as JAK2-STAT3. This hypothesis predicts that any factors that compromise alpha7 function have the potential to negatively impact neuronal viability. For example, such factors could include deficits in the primary neurotransmitter acetylcholine (ACh), underactivity of normal cognitive processes that stimulate alpha7 NNRs (i.e., use-dependency), or the reported binding of beta-amyloid and ApoE4 to alpha7 NNRs, all of which could effectively decouple the receptors from key pro-survival pathways. Since these pathways are known to negatively modulate GSK-3beta, which regulates tau phosphorylation, downstream effects such as tau hyperphosphorylation would be expected to arise. Conversely, the maintenance of normal alpha7 NNR activity by adequate levels of ACh or other NNR agonists would be expected to support normal cholinergic tone, prevent the binding of beta-amyloid and ApoE4 and preserve the integrity of the neurons. We therefore propose that decreased cholinergic tone is at the apex of AD pathophysiology, with factors such as beta-amyloid and ApoE4 playing a contributory role rather that a causal one and hyperphosphorylation of tau representing a detector of concomitant hypocholinergic tone and beta-amyloid deposition. Thus the convergence of beta-amyloid deposition and/or ApoE4 binding and co-localization with alpha7 NNRs, which are favored under conditions of low cholinergic tone, and the downstream cascade of tau hyperphosphorylation through disinhibition of GSK-3beta appear to explain and reconcile many of the discordant findings in this very active area of CNS research.
Collapse
Affiliation(s)
- Merouane Bencherif
- Preclinical Research, Targacept, Inc., Suite 300, Winston-Salem, NC 27101-4165, USA.
| | | |
Collapse
|
16
|
Nicotinic receptors: allosteric transitions and therapeutic targets in the nervous system. Nat Rev Drug Discov 2009; 8:733-50. [PMID: 19721446 DOI: 10.1038/nrd2927] [Citation(s) in RCA: 542] [Impact Index Per Article: 33.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Nicotinic receptors - a family of ligand-gated ion channels that mediate the effects of the neurotransmitter acetylcholine - are among the most well understood allosteric membrane proteins from a structural and functional perspective. There is also considerable interest in modulating nicotinic receptors to treat nervous-system disorders such as Alzheimer's disease, schizophrenia, depression, attention deficit hyperactivity disorder and tobacco addiction. This article describes both recent advances in our understanding of the assembly, activity and conformational transitions of nicotinic receptors, as well as developments in the therapeutic application of nicotinic receptor ligands, with the aim of aiding novel drug discovery by bridging the gap between these two rapidly developing fields.
Collapse
|
17
|
Elliott DA, Tsoi K, Holinkova S, Chan SL, Kim WS, Halliday GM, Rye KA, Garner B. Isoform-specific proteolysis of apolipoprotein-E in the brain. Neurobiol Aging 2009; 32:257-71. [PMID: 19278755 DOI: 10.1016/j.neurobiolaging.2009.02.006] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 02/01/2009] [Accepted: 02/03/2009] [Indexed: 11/19/2022]
Abstract
Apolipoprotein-E (apoE) plays important roles in neurobiology and the apoE4 isoform increases risk for Alzheimer's disease (AD). ApoE peptides are biologically active and may be produced in the brain. It is unclear if apoE proteolysis is dependent on isoform or AD status and this was addressed here. Hippocampus, frontal cortex, occipital lobe and cerebellum samples were homogenized into fractions that were soluble in Tris-buffered saline (TBS), Triton X-100 or guanidine hydrochloride and analysed for apoE fragmentation by Western blotting. Approximately 20% of apoE3 was detected as fragments and this was predominantly as a 25 kDa peptide in TBS-soluble fractions. The concentration of TBS-soluble apoE fragments was two- to three-fold higher in apoE3 compared to apoE4 subjects. This difference was observed in all areas of the brain examined and was not related to AD status. Cathepsin-D treatment generated apoE fragments that were very similar to those detected in brain, however, no apoE isoform-specific differences in susceptibility to cathepsin-D proteolysis were detected. This indicates that proteolytic processing of apoE to form soluble fragments in the human brain is dependent on apoE isoform but not AD status.
Collapse
Affiliation(s)
- David A Elliott
- Prince of Wales Medical Research Institute, Randwick, NSW 2031, Australia
| | | | | | | | | | | | | | | |
Collapse
|
18
|
Buckingham SD, Jones AK, Brown LA, Sattelle DB. Nicotinic acetylcholine receptor signalling: roles in Alzheimer's disease and amyloid neuroprotection. Pharmacol Rev 2009; 61:39-61. [PMID: 19293145 PMCID: PMC2830120 DOI: 10.1124/pr.108.000562] [Citation(s) in RCA: 214] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Alzheimer's disease (AD), the major contributor to dementia in the elderly, involves accumulation in the brain of extracellular plaques containing the beta-amyloid protein (Abeta) and intracellular neurofibrillary tangles of hyperphosphorylated tau protein. AD is also characterized by a loss of neurons, particularly those expressing nicotinic acetylcholine receptors (nAChRs), thereby leading to a reduction in nAChR numbers. The Abeta(1-42) protein, which is toxic to neurons, is critical to the onset and progression of AD. The discovery of new drug therapies for AD is likely to be accelerated by an improved understanding of the mechanisms whereby Abeta causes neuronal death. We examine the evidence for a role in Abeta(1-42) toxicity of nAChRs; paradoxically, nAChRs can also protect neurons when activated by nicotinic ligands. Abeta peptides and nicotine differentially activate several intracellular signaling pathways, including the phosphatidylinositol 3-kinase/v-akt murine thymoma viral oncogene homolog pathway, the extracellular signal-regulated kinase/mitogen-activated protein kinase, and JAK-2/STAT-3 pathways. These pathways control cell death or survival and the secretion of Abeta peptides. We propose that understanding the differential activation of these pathways by nicotine and/or Abeta(1-42) may offer the prospect of new routes to therapy for AD.
Collapse
Affiliation(s)
- Steven D Buckingham
- Medical Research Council Functional Genomics Unit, Department of Physiology Anatomy and Genetics, University of Oxford, South Parks Road, Oxford, UK, OX1 3QX
| | | | | | | |
Collapse
|
19
|
Gay EA, Giniatullin R, Skorinkin A, Yakel JL. Aromatic residues at position 55 of rat alpha7 nicotinic acetylcholine receptors are critical for maintaining rapid desensitization. J Physiol 2007; 586:1105-15. [PMID: 18096596 DOI: 10.1113/jphysiol.2007.149492] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The rat alpha7 nicotinic acetylcholine receptor (nAChR) can undergo rapid onset of desensitization; however, the mechanisms of desensitization are largely unknown. The contribution of a tryptophan (W) residue at position 55 of the rat alpha7 nAChR subunit, which lies within the beta2 strand, was studied by mutating it to other hydrophobic and/or aromatic amino acids, followed by voltage-clamp experiments in Xenopus oocytes. When mutated to alanine, the alpha7-W55A nAChR desensitized more slowly, and recovered from desensitization more rapidly, than wildtype alpha7 nAChRs. The contribution of desensitization was validated by kinetic modelling. Mutating W55 to other aromatic residues (phenylalanine or tyrosine) had no significant effect on the kinetics of desensitization, whereas mutation to various hydrophobic residues (alanine, cysteine or valine) significantly decreased the rate of onset and increased the rate of recovery from desensitization. To gain insight into possible structural rearrangements during desensitization, we probed the accessibility of W55 by mutating W55 to cysteine (alpha7-W55C) and testing the ability of various sulfhydryl reagents to react with this cysteine. Several positively charged sulfhydryl reagents blocked ACh-induced responses for alpha7-W55C nAChRs, whereas a neutral sulfhydryl reagent potentiated responses; residue C55 was not accessible for modification in the desensitized state. These data suggest that W55 plays an important role in both the onset and recovery from desensitization in the rat alpha7 nAChR, and that aromatic residues at position 55 are critical for maintaining rapid desensitization. Furthermore, these data suggest that W55 may be a potential target for modulatory agents operating via hydrophobic interactions.
Collapse
Affiliation(s)
- Elaine A Gay
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services PO Box 12233, Research Triangle Park, NC 27709, USA
| | | | | | | |
Collapse
|