Intra-membrane Oligomerization and Extra-membrane Oligomerization of Amyloid-β Peptide Are Competing Processes as a Result of Distinct Patterns of Motif Interplay

Zhang, Yi-Jiong; Shi, Jing-Ming; Bai, Cai-Juan; Wang, Han; Li, Hai-Yun; Wu, Yi; Ji, Shang‐Rong

doi:10.1074/jbc.m111.281295

Cited by 39 publications

(65 citation statements)

References 50 publications

(80 reference statements)

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“…However, no “monomer only” solution was studied in these experiments, and the monomers may not be the same as the long-time equilibrated species we report here. Also, Zhang et al (2012) have suggested that it is the monomers and not the oligomers that bind to the cell membranes. The reported results are therefore somewhat contradictory.…”

Section: Discussionmentioning

confidence: 99%

Thermodynamically stable amyloid-β monomers have much lower membrane affinity than the small oligomers

Sarkar¹,

Das²,

Maiti³

2013

Front. Physiol.

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Amyloid beta (Aβ) is an extracellular 39–43 residue long peptide present in the mammalian cerebrospinal fluid, whose aggregation is associated with Alzheimer's disease (AD). Small oligomers of Aβ are currently thought to be the key to toxicity. However, it is not clear why the monomers of Aβ are non-toxic, and at what stage of aggregation toxicity emerges. Interactions of Aβ with cell membranes is thought to be the initiator of toxicity, but membrane binding studies with different preparations of monomers and oligomers have not settled this issue. We have earlier found that thermodynamically stable Aβ monomers emerge spontaneously from oligomeric mixtures upon long term incubation in physiological solutions (Nag et al., 2011). Here we show that the membrane-affinity of these stable Aβ monomers is much lower than that of a mixture of monomers and small oligomers (containing dimers to decamers), providing a clue to the emergence of toxicity. Fluorescently labeled Aβ40 monomers show negligible binding to cell membranes of a neuronal cell line (RN46A) at physiological concentrations (250 nM), while oligomers at the same concentrations show strong binding within 30 min of incubation. The increased affinity most likely does not require any specific neuronal receptor, since this difference in membrane-affinity was also observed in a somatic cell-line (HEK 293T). Similar results are also obtained for Aβ42 monomers and oligomers. Minimal amount of cell death is observed at these concentrations even after 36 h of incubation. It is likely that membrane binding precedes subsequent slower toxic events induced by Aβ. Our results (a) provide an explanation for the non-toxic nature of Aβ monomers, (b) suggest that Aβ toxicity emerges at the initial oligomeric phase, and (c) provide a quick assay for monitoring the benign-to-toxic transformation of Aβ.

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Section: Discussionmentioning

confidence: 99%

Thermodynamically stable amyloid-β monomers have much lower membrane affinity than the small oligomers

Sarkar¹,

Das²,

Maiti³

2013

Front. Physiol.

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“…As discussed earlier in the summary of the model membrane work, both mechanisms could certainly be at play, with direct binding from solution generally predominating at higher concentrations and in‐membrane oligomer formation dominating at lower ones. As recently hypothesized by Zhang et al ., Aβ oligomers formed from monomer within the membrane and those formed in solution (before membrane‐binding) may even induce toxicity by two entirely separate mechanisms …”

Section: Binding and Oligomer Formation: Live Cell Membranesmentioning

confidence: 99%

“…As recently hypothesized by Zhang et al, Ab oligomers formed from monomer within the membrane and those formed in solution (before membrane-binding) may even induce toxicity by two entirely separate mechanisms. 63…”

Section: Binding and Oligomer Formation: Live Cell Membranesmentioning

confidence: 99%

Structural evolution and membrane interactions of Alzheimer's amyloid‐beta peptide oligomers: New knowledge from single‐molecule fluorescence studies

2014

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Amyloid-b peptide (Ab) oligomers may represent the proximal neurotoxin in Alzheimer's disease. Single-molecule microscopy (SMM) techniques have recently emerged as a method for overcoming the innate difficulties of working with amyloid-b, including the peptide's low endogenous concentrations, the dynamic nature of its oligomeric states, and its heterogeneous and complex membrane interactions. SMM techniques have revealed that small oligomers of the peptide bind to model membranes and cells at low nanomolar-to-picomolar concentrations and diffuse at rates dependent on the membrane characteristics. These methods have also shown that oligomers grow or dissociate based on the presence of specific inhibitors or promoters and on the ratio of Ab40 to Ab42. Here, we discuss several types of single-molecule imaging that have been applied to the study of Ab oligomers and their membrane interactions. We also summarize some of the recent insights SMM has provided into oligomer behavior in solution, on planar lipid membranes, and on living cell membranes. A brief Abbreviations: AD, Alzheimer's Disease; ADDL, amyloid-derived diffusible ligand; Ab, amyloid-b peptide; Ab40, 40-residue version of Ab; Ab42, 42-residue version of Ab; Ab*56, dodecameric Ab oligomer; APP, amyloid precursor protein; cTCCD, confocal two-color coincidence detection; D, diffusion coefficient; FAM, carboxyfluorescein; FRAP, fluorescence recovery after photobleaching; FRET, fluorescence resonance energy transfer; GUV, giant unilamellar vesicle; hAPP, human Amyloid Precursor Protein; HFIP, hexafluoroisopropanol; HL488, HiLyte Fluor 488; HL555, HiLyte Fluor 555; HL647, HiLyte Fluor 647; MSD, mean square displacement; SMM, single-molecule microscopy; TAMRA, carboxytetramethylrhodamine; TIRF, total internal reflection fluorescence. overview of the current limitations of the technique, including the lack of sensitive assays for Ab-induced toxicity, is included in hopes of inspiring future development in this area of research.

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“…Membrane Insertion-The interactions of synthetic peptides with lipid membrane were examined with Trough-S microbalance (Kibron, Finland) (27,28). The trough was filled with TBS followed by spreading of lipid onto the buffer surface.…”

Section: Methodsmentioning

confidence: 99%

An Intrinsically Disordered Motif Mediates Diverse Actions of Monomeric C-reactive Protein

Wang

Meng

et al. 2016

Journal of Biological Chemistry

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C-reactive protein (CRP) 3 is a major human acute phase reactant composed of five identical subunits (1, 2). Accumulating evidence demonstrates that the actions of CRP depend on conformation and localization (3-5). CRP is primarily produced by the liver and circulates in the blood as a pentamer but is induced to dissociate into subunits (monomeric CRP, mCRP) upon interaction with the microenvironment at inflammatory loci (6 -18). mCRP exhibits markedly enhanced activities and recognizes an expanded list of binding partners. Following reduction of the intra-subunit disulfide bond, mCRP can be further activated (19). The degradation of mCRP, on the other hand, would generate bioactive fragments showing anti-inflammatory actions (20 -23). The differential contributions of these CRP conformations at distinct locations may therefore account for the intense controversies regarding the function of CRP in animal models and in clinical studies (3-5). mCRP appears to be the major conformation of CRP that regulates local inflammation (3-5), yet how it acts remains incompletely understood. In particular, though the markedly enhanced binding capability of mCRP underlies its actions, little is known through which sites mCRP recognizes diverse ligands. Consequently, no means is available to specifically modulate the actions of mCRP, which is necessary for clarifying the exact contributions of different CRP conformations in vitro and in vivo. The current study was designed to identify the recognition site of mCRP for ligand binding. The results unexpectedly demonstrated cholesterol binding sequence (CBS) as a versatile motif that mediates the interactions of mCRP with different types of ligands, including two newly identified herein. We further showed that synthetic CBS peptide was able to inhibit the proinflammatory actions of mCRP both in vitro and in vivo. Hence, optimized CBS peptide may be developed as a potential inhibitor of mCRP. Experimental ProceduresReagents-Human native CRP (purity Ͼ 99%) purified from ascites was purchased from the BindingSite (Birmingham, UK; catalogue number: BP300.X). mCRP and acylated Cys-mutated mCRP was prepared as described (19,24). Proteins were dialyzed to remove NaN 3 , and passed through Detoxi-Gel Columns (Thermo Fisher Scientific, Rockford, IL; catalogue number: 20344) to remove endotoxin when necessary. CRP peptides (purity Ͼ 98%) were synthesized by Science Peptide Biological Technology (Shanghai, China). Lyophilized peptides were reconstituted aseptically with DMSO at 40 mg/ml and stored at Ϫ20°C in aliquots or kept at 4°C for a maximum of 1 week.

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Intra-membrane Oligomerization and Extra-membrane Oligomerization of Amyloid-β Peptide Are Competing Processes as a Result of Distinct Patterns of Motif Interplay

Cited by 39 publications

References 50 publications

Thermodynamically stable amyloid-β monomers have much lower membrane affinity than the small oligomers

Thermodynamically stable amyloid-β monomers have much lower membrane affinity than the small oligomers

Structural evolution and membrane interactions of Alzheimer's amyloid‐beta peptide oligomers: New knowledge from single‐molecule fluorescence studies

An Intrinsically Disordered Motif Mediates Diverse Actions of Monomeric C-reactive Protein

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