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Larsen EM, Wilson MR, Taylor RE. Conformation-activity relationships of polyketide natural products. Nat Prod Rep 2015; 32:1183-206. [PMID: 25974024 PMCID: PMC4443481 DOI: 10.1039/c5np00014a] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Polyketides represent an important class of secondary metabolites that interact with biological targets connected to a variety of disease-associated pathways. Remarkably, nature's assembly lines, polyketide synthases, manufacture these privileged structures through a combinatorial mixture of just a few structural units. This review highlights the role of these structural elements in shaping a polyketide's conformational preferences, the use of computer-based molecular modeling and solution NMR studies in the identification of low-energy conformers, and the importance of conformational analogues in probing the bound conformation. In particular, this review covers several examples wherein conformational analysis complements classic structure-activity relationships in the design of biologically active natural product analogues.
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Affiliation(s)
- Erik M Larsen
- University of Notre Dame, Department of Chemistry & Biochemistry, 250 Nieuwland Science Hall, Notre Dame, Indiana, USA.
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2
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Kraft M, Poudel YB, Kedei N, Lewin N, Peach ML, Blumberg PM, Keck GE. Synthesis of a des-B-ring bryostatin analogue leads to an unexpected ring expansion of the bryolactone core. J Am Chem Soc 2014; 136:13202-8. [PMID: 25207434 PMCID: PMC4183620 DOI: 10.1021/ja5078188] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Indexed: 11/28/2022]
Abstract
A convergent synthesis of a des-B-ring bryostatin analogue is described. This analogue was found to undergo an unexpected ring expansion of the bryolactone core to generate the corresponding 21-membered macrocycle. The parent analogue and the ring-expanded product both displayed nanomolar binding affinity for PKC. Despite containing A-ring substitution identical to that of bryostatin 1 and displaying bryostatin-like biological function, the des-B-ring analogues displayed a phorbol-like biological function in cells. These studies shed new light on the role of the bryostatin B-ring in conferring bryo-like biological function to bryostatin analogues.
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Affiliation(s)
- Matthew
B. Kraft
- Department
of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Yam B. Poudel
- Department
of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Noemi Kedei
- Laboratory
of Cancer Biology and Genetics, National
Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4255, United States
| | - Nancy
E. Lewin
- Laboratory
of Cancer Biology and Genetics, National
Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4255, United States
| | - Megan L. Peach
- Basic Science Program,
Leidos Biomedical Research, Inc., Chemical Biology Laboratory, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702, United States
| | - Peter M. Blumberg
- Laboratory
of Cancer Biology and Genetics, National
Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4255, United States
| | - Gary E. Keck
- Department
of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
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3
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Cragg GM, Grothaus PG, Newman DJ. New horizons for old drugs and drug leads. JOURNAL OF NATURAL PRODUCTS 2014; 77:703-23. [PMID: 24499205 DOI: 10.1021/np5000796] [Citation(s) in RCA: 168] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
There is mounting urgency to find new drugs for the treatment of serious infectious diseases and cancer that are rapidly developing resistance to previously effective drugs. One approach to addressing this need is through drug repurposing, which refers to the discovery of new useful activities for "old" clinically used drugs through screening them against relevant disease targets. A large number of potential drug that, for various reasons, have failed to advance to clinical and commercial use can be added to the candidates available for such purposes. The application of new techniques and methodology developed through the impressive progress made in multidisciplinary, natural product-related research in recent years should aid substantially in expediting the discovery and development process. This review briefly outlines some of these developments as applied to a number of selected natural product examples, which may also include advances in chemical synthesis of derivatives with extended biological activities.
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Affiliation(s)
- Gordon M Cragg
- Natural Products Branch, Developmental Therapeutics Program, Division of Cancer Treatment and Diagnosis, Frederick National Laboratory , P.O. Box B, Frederick, Maryland 21702, United States
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4
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Xu C, Liu QY, Alkon DL. PKC activators enhance GABAergic neurotransmission and paired-pulse facilitation in hippocampal CA1 pyramidal neurons. Neuroscience 2014; 268:75-86. [PMID: 24637095 DOI: 10.1016/j.neuroscience.2014.03.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2013] [Revised: 03/05/2014] [Accepted: 03/06/2014] [Indexed: 11/18/2022]
Abstract
Bryostatin-1, a potent agonist of protein kinase C (PKC), has recently been found to enhance spatial learning and long-term memory in rats, mice, rabbits and the nudibranch Hermissenda, and to exert profound neuroprotective effects on Alzheimer's disease (AD) in transgenic mice. However, details of the mechanistic effects of bryostatin on learning and memory remain unclear. To address this issue, whole-cell recording, a dual-recording approach and extracellular recording techniques were performed on young (2-4months) Brown-Norway rats. We found that bath-applied bryostatin-1 significantly increased the frequency and amplitude of spontaneous inhibitory postsynaptic currents (sIPSCs). The firing rate of GABAergic interneurons significantly was also increased as recorded with a loosely-attached extracellular recording configuration. Simultaneous recordings from communicating cell pairs of interneuron and pyramidal neuron revealed unique activity-dependent properties of GABAergic synapses. Furthermore, the bryostatin-induced increase of the frequency and amplitude of IPSCs was blocked by methionine enkephalin which selectively suppressed the excitability of interneurons. Pretreatment with RO-32-0432, a relatively specific PKCα antagonist, blocked the effect of bryostatin on sIPSCs. Finally, bryostatin increased paired-pulse ratio of GABAergic synapses that lasted for at least 20min while pretreatment with RO-32-0432 significantly reduced the ratio. In addition, 8-[2-(2-pentyl-cyclopropylmethl)-cyclopropyl]-octanoic acid (DCP-LA), a selective PKCε activator, also increased the frequency and amplitude of sIPSCs. Taken together, these results suggest that bryostatin enhances GABAergic neurotransmission in pyramidal neurons by activating the PKCα & ε-dependent pathway and by a presynaptic mechanism with excitation of GABAergic interneurons. These effects of bryostatin on GABAergic transmissions and modifiability may contribute to the improvement of learning and memory previously observed to be induced by bryostatin.
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Affiliation(s)
- C Xu
- Blanchette Rockefeller Neurosciences Institute, Morgantown, WV 26506, United States of America.
| | - Q-Y Liu
- Blanchette Rockefeller Neurosciences Institute, Morgantown, WV 26506, United States of America
| | - D L Alkon
- Blanchette Rockefeller Neurosciences Institute, Morgantown, WV 26506, United States of America
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5
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Nelson TJ, Sen A, Alkon DL, Sun MK. Adduct formation in liquid chromatography-triple quadrupole mass spectrometric measurement of bryostatin 1. J Chromatogr B Analyt Technol Biomed Life Sci 2013; 944:55-62. [PMID: 24291721 DOI: 10.1016/j.jchromb.2013.11.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 11/05/2013] [Accepted: 11/10/2013] [Indexed: 11/25/2022]
Abstract
Bryostatin 1, a potential anti-Alzheimer drug, is effective at subnanomolar concentrations. Measurement is complicated by the formation of low m/z degradation products and the formation of adducts with various cations, which make accurate quantitation difficult. Adduct formation caused the sample matrix or mobile phase to partition bryostatin 1 into products of different mass. Degradation of the 927 [M+Na](+) ion to a 869m/z product was strongly influenced by ionization conditions. We validated a bryostatin 1 assay in biological tissues using capillary column HPLC with nanospray ionization (NSI) in a triple-quadrupole mass spectrometer in selected reaction monitoring (SRM) mode. Adduct formation was controlled by adding 1mM acetic acid and 0.1mM sodium acetate to the HPLC buffer, maximizing the formation of the [M+Na](+) ion. Efficient removal of contaminating cholesterol from the sample during solvent extraction was also critical. The increased sensitivity provided by NSI and capillary-bore columns and the elimination of signal partitioning due to adduct formation and degradation in the ionization source enabled a detection limit of 1×10(-18)mol of bryostatin 1 and a LLOQ of 3×10(-18)mol from 1μl of sample. Bryostatin 1 at low pmol/l concentrations enabled measurement in brain and other tissues without the use of radioactive labels. Despite bryostatin 1's high molecular weight, considerable brain access was observed, with peak brain concentrations exceeding 8% of the peak blood plasma concentrations. Bryostatin 1 readily crosses the blood-brain barrier, reaching peak concentrations of 0.2nM, and specifically activates and translocates brain PKCɛ.
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Affiliation(s)
- Thomas J Nelson
- Blanchette Rockefeller Neurosciences Institute, 8 Medical Center Drive, Morgantown, WV 26505, USA.
| | - Abhik Sen
- Blanchette Rockefeller Neurosciences Institute, 8 Medical Center Drive, Morgantown, WV 26505, USA
| | - Daniel L Alkon
- Blanchette Rockefeller Neurosciences Institute, 8 Medical Center Drive, Morgantown, WV 26505, USA
| | - Miao-Kun Sun
- Blanchette Rockefeller Neurosciences Institute, 8 Medical Center Drive, Morgantown, WV 26505, USA
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6
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Microbial natural products: molecular blueprints for antitumor drugs. J Ind Microbiol Biotechnol 2013; 40:1181-210. [PMID: 23999966 DOI: 10.1007/s10295-013-1331-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 08/07/2013] [Indexed: 12/18/2022]
Abstract
Microbes from two of the three domains of life, the Prokarya, and Eukarya, continue to serve as rich sources of structurally complex chemical scaffolds that have proven to be essential for the development of anticancer therapeutics. This review describes only a handful of exemplary natural products and their derivatives as well as those that have served as elegant blueprints for the development of novel synthetic structures that are either currently in use or in clinical or preclinical trials together with some of their earlier analogs in some cases whose failure to proceed aided in the derivation of later compounds. In every case, a microbe has been either identified as the producer of secondary metabolites or speculated to be involved in the production via symbiotic associations. Finally, rapidly evolving next-generation sequencing technologies have led to the increasing availability of microbial genomes. Relevant examples of genome mining and genetic manipulation are discussed, demonstrating that we have only barely scratched the surface with regards to harnessing the potential of microbes as sources of new pharmaceutical leads/agents or biological probes.
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7
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Yi P, Schrott L, Castor TP, Alexander JS. Bryostatin-1 vs. TPPB: dose-dependent APP processing and PKC-α, -δ, and -ε isoform activation in SH-SY5Y neuronal cells. J Mol Neurosci 2012; 48:234-44. [PMID: 22700373 PMCID: PMC3413820 DOI: 10.1007/s12031-012-9816-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 05/16/2012] [Indexed: 01/17/2023]
Abstract
Activation of the α-secretase processing pathway of amyloid precursor protein (APP) is recognized as an important mechanism which diverts APP processing from production of beta-amyloid (Aβ) to non toxic sAPPα, decreasing Alzheimer’s disease (AD) plaque formation and AD-associated cognitive deficits. Two potent classes of PKC modulators can activate the α-secretase pathway, the benzo/indolactams and bryostatin/bryologues. While both modulate PKC-dependent APP processing, no direct comparisons of their relative pharmacological potencies have been accomplished which could assist in the development of AD therapies. In this study, we measured the activation of α-secretase APP processing and PKC-α, -δ, and -ε induced by the benzolactam-APP modulator TPPB and bryostatin-1 in the neuroblastoma cell line SH-SY5Y which expresses APP and α- and β-secretase processing mechanisms. Bryostatin-1 produced a more rapid, potent, and sustained activation of α-secretase APP processing than TPPB and selectively activated PKC-δ and PKC-ε. Although TPPB also activated α-secretase, its potency was approximately 10- to 100-fold lower, possibly reflecting lower PKC-δ and -ε activation. Because bryostatin-1 is a highly potent PKC-δ and -ε activator which activates α-secretase APP processing, further characterization of bryostatin-1/bryologues may help refine their use as important tools for the clinical management of AD.
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Affiliation(s)
- P. Yi
- Department of Molecular and Cellular Physiology, LSU Health, 1501 Kings Hwy, Shreveport, LA 71130 USA
| | - L. Schrott
- Department of Pharmacology, Toxicology and Neuroscience, LSU Health, 1501 Kings Hwy, Shreveport, LA 71130 USA
| | | | - J. S. Alexander
- Department of Molecular and Cellular Physiology, LSU Health, 1501 Kings Hwy, Shreveport, LA 71130 USA
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Sun MK, Alkon DL. Activation of protein kinase C isozymes for the treatment of dementias. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2012; 64:273-302. [PMID: 22840750 DOI: 10.1016/b978-0-12-394816-8.00008-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Memories are much more easily impaired than improved. Dementias, a lasting impairment of memory function, occur in a variety of cognitive disorders and become more clinically dominant as the population ages. Protein kinase C is one of the "cognitive kinases," and plays an essential role in both memory acquisition and maintenance. Deficits in protein kinase C (PKC) signal cascades in neurons represent one of the earliest changes in the brains of patients with Alzheimer's disease (AD) and other types of memory impairment, including those related to cerebral ischemia and ischemic stroke. Inhibition or impairment of PKC activity results in compromised learning and memory, whereas an appropriate activation of certain PKC isozymes leads to an enhancement of learning and memory and/or antidementic effects. In preclinical studies, PKC activators have been shown to increase the expression and activity of PKC isozymes, thereby restoring PKC signaling and downstream activity, including stimulation of neurotrophic activity, synaptic/structural remodeling, and synaptogenesis in the hippocampus and related cortical areas. PKC activators also reduce the accumulation of neurotoxic amyloid and tau protein hyperphosphorylation and support anti-apoptotic processes in the brain. These observations strongly suggest that PKC pharmacology may represent an attractive area for the development of effective cognition-enhancing therapeutics for the treatment of dementias.
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Affiliation(s)
- Miao-Kun Sun
- Blanchette Rockefeller Neurosciences Institute, Morgantown, WV, USA
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Trindade-Silva AE, Lim-Fong GE, Sharp KH, Haygood MG. Bryostatins: biological context and biotechnological prospects. Curr Opin Biotechnol 2011; 21:834-42. [PMID: 20971628 DOI: 10.1016/j.copbio.2010.09.018] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 09/25/2010] [Accepted: 09/29/2010] [Indexed: 11/18/2022]
Abstract
Bryostatins are a family of protein kinase C modulators that have potential applications in biomedicine. Found in miniscule quantities in a small marine invertebrate, lack of supply has hampered their development. In recent years, bryostatins have been shown to have potent bioactivity in the central nervous system, an uncultivated marine bacterial symbiont has been shown to be the likely natural source of the bryostatins, the bryostatin biosynthetic genes have been identified and characterized, and bryostatin analogues with promising biological activity have been developed and tested. Challenges in the development of bryostatins for biomedical and biotechnological application include the cultivation of the bacterial symbiont and heterologous expression of bryostatin biosynthesis genes. Continued exploration of the biology as well as the symbiotic origin of the bryostatins presents promising opportunities for discovery of additional bryostatins, and new functions for bryostatins.
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Affiliation(s)
- Amaro E Trindade-Silva
- Instituto de Química de São Carlos, Universidade de São Paulo CP 780, CEP 13560-970, São Carlos, SP, Brazil
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10
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PKC activator therapeutic for mild traumatic brain injury in mice. Neurobiol Dis 2010; 41:329-37. [PMID: 20951803 DOI: 10.1016/j.nbd.2010.10.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Revised: 09/25/2010] [Accepted: 10/02/2010] [Indexed: 01/08/2023] Open
Abstract
Traumatic brain injury (TBI) is a frequent consequence of vehicle, sport and war related injuries. More than 90% of TBI patients suffer mild injury (mTBI). However, the pathologies underlying the disease are poorly understood and treatment modalities are limited. We report here that in mice, the potent PKC activator bryostatin1 protects against mTBI induced learning and memory deficits and reduction in pre-synaptic synaptophysin and post-synaptic spinophylin immunostaining. An effective treatment has to start within the first 8h after injury, and includes 5 × i.p. injections over a period of 14 days. The treatment is dose dependent. Exploring the effects of the repeated bryostatin1 treatment on the processing of the amyloid precursor protein, we found that the treatment induced an increase in the putative α-secretase ADAM10 and a reduction in β-secretase activities. Both these effects could contribute towards a reduction in β-amyloid production. These results suggest that bryostatin1 protects against mTBI cognitive and synaptic sequela by rescuing synapses, which is possibly mediated by an increase in ADAM10 and a decrease in BACE1 activity. Since bryostatin1 has already been extensively used in clinical trials as an anti-cancer drug, its potential as a remedy for the short- and long-term TBI sequelae is quite promising.
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Hale KJ, Manaviazar S. New approaches to the total synthesis of the bryostatin antitumor macrolides. Chem Asian J 2010; 5:704-54. [PMID: 20354984 DOI: 10.1002/asia.200900634] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In this Focus Review, we give an overview of various bryostatin total syntheses. We also discuss the synthesis of various bryostatin analogues and their biological activity. Work reviewed includes that of Masamune, Evans, Nishiyama and Yamamura, Hale and Manaviazar, Trost, Wender, Keck, Burke, Thomas, and Krische. Our coverage is primarily for the period 2001-2009, since detailed reviews already exist on bryostatin total synthesis work and biology up to this time.
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Affiliation(s)
- Karl J Hale
- School of Chemistry & Chemical Engineering, Queen's Universty Belfast, Stranmillis Road, Belfast BT9 5AG, Northern Ireland, UK.
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Nelson TJ, Cui C, Luo Y, Alkon DL. Reduction of beta-amyloid levels by novel protein kinase C(epsilon) activators. J Biol Chem 2009; 284:34514-21. [PMID: 19850930 PMCID: PMC2787312 DOI: 10.1074/jbc.m109.016683] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Revised: 10/20/2009] [Indexed: 12/12/2022] Open
Abstract
Isoform-specific protein kinase C (PKC) activators may be useful as therapeutic agents for the treatment of Alzheimer disease. Three new epsilon-specific PKC activators, made by cyclopropanation of polyunsaturated fatty acids, have been developed. These activators, AA-CP4, EPA-CP5, and DHA-CP6, activate PKCepsilon in a dose-dependent manner. Unlike PKC activators that bind to the 1,2-diacylglycerol-binding site, such as bryostatin and phorbol esters, which produce prolonged down-regulation, the new activators produced sustained activation of PKC. When applied to cells expressing human APPSwe/PS1delta, which produce large quantities of beta-amyloid peptide (Abeta), DCP-LA and DHA-CP6 reduced the intracellular and secreted levels of Abeta by 60-70%. In contrast to the marked activation of alpha-secretase produced by PKC activators in fibroblasts, the PKC activators produced only a moderate and transient activation of alpha-secretase in neuronal cells. However, they activated endothelin-converting enzyme to 180% of control levels, suggesting that the Abeta-lowering ability of these PKCepsilon activators is caused by increasing the rate of Abeta degradation by endothelin-converting enzyme and not by activating nonamyloidogenic amyloid precursor protein metabolism.
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Affiliation(s)
- Thomas J Nelson
- Blanchette Rockefeller Neurosciences Institute, Morgantown, West Virginia 26506, USA.
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