Protease‐activated alpha‐2‐macroglobulin can inhibit amyloid formation via two distinct mechanisms

Wyatt, Amy R.; Constantinescu, Patrick; Ecroyd, Heath; Dobson, Christopher M.; Wilson, Mark R.; Kumita, Janet R.; Yerbury, Justin J.

doi:10.1016/j.febslet.2013.01.020

Cited by 42 publications

(28 citation statements)

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“…When activated by proteases, alpha2M functions as an extracellular chaperone that inhibits amorphous and fibrillar protein aggregation (Wyatt, et al, 2013). It is also implicated in the clearance of the extracellular Aβ constituent of amyloid plaques, where it acts as an extracellular chaperone that helps control amyloid formation and toxicity in vivo (Wilson, et al, 2008; Yerbury, et al, 2009, Yerbury and Wilson, 2010).…”

Section: Discussionmentioning

confidence: 99%

Association of cerebrospinal fluid Aβ42 with A2M gene in cognitively normal subjects

Millard¹,

Lutz²,

Li³

et al. 2014

Neurobiology of Aging

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Low cerebrospinal fluid (CSF) Aβ42 levels correlate with increased brain Aβ deposition in Alzheimer’s disease (AD), which suggests a disruption in the degradation and clearance of Aβ from the brain. In addition, APOE ε4 carriers have lower CSF Aβ42 levels than non-carriers. The hypothesis of this investigation was that CSF Aβ42 levels correlate with regulatory region variation in genes that are biologically associated with degradation or clearance of Aβ from the brain. CSF Aβ42 levels were tested for associations with Aβ degradation and clearance genes and APOE ε4. Twenty-four SNPs located within the 5′ and 3′ regions of 12 genes were analyzed. The study sample consisted of 99 AD patients and 168 cognitively normal control subjects. CSF Aβ42 levels were associated with APOE ε4 status in controls but not in AD patients; A2M regulatory region SNPs were also associated with CSF Aβ42 levels in controls, but not in AD patients, even after adjusting for APOE ε4. These results suggest that genetic variation within the A2M gene influences CSF Aβ42 levels.

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Section: Discussionmentioning

confidence: 99%

Association of cerebrospinal fluid Aβ42 with A2M gene in cognitively normal subjects

Millard¹,

Lutz²,

Li³

et al. 2014

Neurobiology of Aging

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“…α 2 M was purified from human plasma as previously described (13). Oxidized α 2 M was prepared by adding various amounts of NaOCl to α 2 M [690 nM in phosphate buffered saline (pH 7.4); PBS; Thermo Scientific] and incubating overnight at room temperature (RT) unless otherwise specified.…”

Section: Methodsmentioning

confidence: 99%

“…Aβ 1-42 (5 μM) was incubated in the presence or absence of native or oxidized α 2 M (250 nM) for 115 min at 28°C with shaking. The samples were then applied to holey carbon-coated nickel grids (Agar Scientific) and imaged at the Multi-Imaging Centre in the Department of Physiology, Development and Neuroscience (University of Cambridge, Cambridge, UK), as previously described (13).…”

Section: Ansmentioning

confidence: 99%

“…Although our understanding of extracellular proteostasis has increased in recent years, it is still limited compared with our extensive knowledge of the mechanisms comprising intracellular proteostasis (12). Several in vitro studies have shown that α 2 M can inhibit both fibril formation by amyloidogenic proteins and peptides (13)(14)(15)(16) and stress-induced amorphous aggregation of other systems (17). In addition, recent studies have shown that α 2 M can protect neurons from toxic oligomers of the protein HypF-N and the Alzheimer's diseaserelevant amyloid β-peptide (Aβ ) by preventing them from binding to the cell surface (18,19).…”

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confidence: 99%

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Hypochlorite-induced structural modifications enhance the chaperone activity of human α₂-macroglobulin

Wyatt

Kumita

Mifsud

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Hypochlorite, an oxidant generated in vivo by the innate immune system, kills invading pathogens largely by inducing the misfolding of microbial proteins. Concomitantly, the nonspecific activity of hypochlorite also damages host proteins, and the accumulation of damaged (misfolded) proteins is implicated in the pathology of a variety of debilitating human disorders (e.g., Alzheimer's disease, atherosclerosis, and arthritis). It is well-known that cells respond to oxidative stress by up-regulating proteostasis machinery, but the direct activation of mammalian chaperones by hypochlorite has not, to our knowledge, been previously reported. In this study, we show that hypochlorite-induced modifications of human α 2 -macroglobulin (α 2 M) markedly increase its chaperone activity by generating species, particularly dimers formed by dissociation of the native tetramer, which have enhanced surface hydrophobicity. Moreover, dimeric α 2 M is generated in whole-blood plasma in the presence of physiologically relevant amounts of hypochlorite. The chaperone activity of hypochlorite-modified α 2 M involves the formation of stable soluble complexes with misfolded client proteins, including heat-denatured enzymes, oxidized fibrinogen, oxidized LDL, and native or oxidized amyloid β-peptide (Aβ 1-42 ). Here, we show that hypochlorite-modified α 2 M delivers its misfolded cargo to lipoprotein receptors on macrophages and reduces Aβ 1-42 neurotoxicity. Our results support the conclusion that α 2 M is a specialized chaperone that prevents the extracellular accumulation of misfolded and potentially pathogenic proteins, particularly during innate immune system activity. molecular chaperone | inflammation | protein folding | clearance H ypochlorite, a potent oxidant produced by immune cells through the myeloperoxidase-H 2 O 2 -chloride system, kills invading microbes predominately by inducing the misfolding and aggregation of their proteins (1). The effects of hypochlorite, however, are nonspecific; therefore, when generated in vivo, the host organism suffers collateral damage (reviewed in refs. 2 and 3). During inflammation, hypochlorite production is accompanied by additional stresses, which are themselves capable of inducing protein misfolding (e.g., increased temperature and lowered pH); it is, therefore, not surprising that, in a large number of diseases [e.g., atherosclerosis (4), Alzheimer's disease (5, 6), age-related macular degeneration (7), and arthritis (8)], inflammatory pathology is associated with the accumulation of misfolded proteins.α 2 -Macroglobulin (α 2 M) is a highly abundant secreted protein that is best known for its ability to trap proteases (9); α 2 M can, however, interact with a broad range of molecules, and consequently, many other biological roles have been suggested, including targeting cytokines for clearance, sequestration of zinc, and opsonization of bacteria (reviewed in ref. 10). Furthermore, α 2 M has been identified as one of a small number of abundant extracellular chaperones (11). Although our un...

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“…Intriguingly, another extracellular chaperone, A2M (-2-macroglobulin) [75], is also a broad-spectrum proteinase inhibitor, with well-known action against MMPs [76]. It might be speculated that proteinase inhibition is part of an anti-inflammatory suite of activities shared by at least some of the extracellular chaperones.…”

Section: Chaperone Activity and Proteinase Inhibitionmentioning

confidence: 99%

Clusterin in the eye: An old dog with new tricks at the ocular surface

Fini

Bauskar

Jeong

et al. 2016

Experimental Eye Research

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, M. R. (2016). Clusterin in the eye: an old dog with new tricks at the ocular surface. Experimental Eye Research, Clusterin in the eye: an old dog with new tricks at the ocular surface AbstractThe multifunctional protein clusterin (CLU) was first described in 1983 as a secreted glycoprotein present in ram rete testis fluid that enhanced aggregation ('clustering') of a variety of cells in vitro. It was also independently discovered in a number of other systems. By the early 1990s, CLU was known under many names and its expression had been demonstrated throughout the body, including in the eye. Its homeostatic activities in proteostasis, cytoprotection, and anti-inflammation have been well documented, however its roles in health and disease are still not well understood. CLU is prominent at fluid-tissue interfaces, and in 1996 it was demonstrated to be the most highly expressed transcript in the human cornea, the protein product being localized to the apical layers of the mucosal epithelia of the cornea and conjunctiva. CLU protein is also present in human tears. Using a preclinical mouse model for desiccating stress that mimics human dry eye disease, the authors recently demonstrated that CLU prevents and ameliorates ocular surface barrier disruption by a remarkable sealing mechanism dependent on attainment of a critical all-or-none concentration in the tears. When the CLU level drops below the critical all-or-none threshold, the barrier becomes vulnerable to desiccating stress. CLU binds selectively to the ocular surface subjected to desiccating stress in vivo, and in vitro to LGALS3 (galectin-3), a key barrier component. Positioned in this way, CLU not only physically seals the ocular surface barrier, but it also protects the barrier cells and prevents further damage to barrier structure. CLU depletion from the ocular surface epithelia is seen in a variety of inflammatory conditions in humans and mice that lead to squamous metaplasia and a keratinized epithelium. This suggests that CLU might have a specific role in maintaining mucosal epithelial differentiation, an idea that can now be tested using the mouse model for desiccating stress. Most excitingly, the new findings suggest that CLU could serve as a novel biotherapeutic for dry eye disease. Competing Interests: US patent 9,241,974 B2 entitled "Clusterin pharmaceuticals and treatment methods using the same" (inventors: MEF and SJ), assigned to the University of Southern California, is connected with this work. MEF holds a management position with Proteris Biotech, Inc., Pasadena, CA, which is developing Protearin for dry eye based on clusterin. MRW declares that he has no competing interests. Page 3 of 65 AbstractThe multifunctional protein clusterin (CLU) was first described in 1983 as a secreted glycoprotein present in ram rete testis fluid that enhanced aggregation ('clustering') of a variety of cells in vitro. It was also independently discovered in a number of other systems. By the early 1990s, CLU was known under many names and its expression had bee...

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Protease‐activated alpha‐2‐macroglobulin can inhibit amyloid formation via two distinct mechanisms

Abstract: Highlights► α2M is an extracellular chaperone able to inhibit protein aggregation. ► Protease–α2M complexes can degrade amyloidogenic substrates or act as a chaperone. ► Activated α2M may play an important role in preventing protein deposition in vivo.

Cited by 42 publications

References 29 publications

Association of cerebrospinal fluid Aβ42 with A2M gene in cognitively normal subjects

Association of cerebrospinal fluid Aβ42 with A2M gene in cognitively normal subjects

Hypochlorite-induced structural modifications enhance the chaperone activity of human α₂-macroglobulin

Clusterin in the eye: An old dog with new tricks at the ocular surface

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Protease‐activated alpha‐2‐macroglobulin can inhibit amyloid formation via two distinct mechanisms

Abstract: Highlights► α2M is an extracellular chaperone able to inhibit protein aggregation. ► Protease–α2M complexes can degrade amyloidogenic substrates or act as a chaperone. ► Activated α2M may play an important role in preventing protein deposition in vivo.

Cited by 42 publications

References 29 publications

Association of cerebrospinal fluid Aβ42 with A2M gene in cognitively normal subjects

Association of cerebrospinal fluid Aβ42 with A2M gene in cognitively normal subjects

Hypochlorite-induced structural modifications enhance the chaperone activity of human α2-macroglobulin

Clusterin in the eye: An old dog with new tricks at the ocular surface

Contact Info

Product

Resources

About

Hypochlorite-induced structural modifications enhance the chaperone activity of human α₂-macroglobulin