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Full-Text Articles in Physical Sciences and Mathematics
Carboxymethylated-K-Casein: A Convenient Tool For The Identification Of Polyphenolic Inhibitors Of Amyloid Fibril Formation, John A. Carver, Peter J. Duggan, Heath Ecroyd, Yanqin Liu, Adam G. Meyer, C E. Tranberg
Carboxymethylated-K-Casein: A Convenient Tool For The Identification Of Polyphenolic Inhibitors Of Amyloid Fibril Formation, John A. Carver, Peter J. Duggan, Heath Ecroyd, Yanqin Liu, Adam G. Meyer, C E. Tranberg
Heath Ecroyd
Reduced and carboxymethylated-κ-casein (RCM-κ-CN) is a milk-derived amyloidogenic protein that readily undergoes nucleation-dependent aggregation and amyloid fibril formation via a similar pathway to disease-specific amyloidogenic peptides like amyloid beta (Aβ), which is associated with Alzheimer’s disease. In this study, a series of flavonoids, many known to be inhibitors of Aβ fibril formation, were screened for their ability to inhibit RCM-κ-CN fibrilisation, and the results were compared with literature data on Aβ inhibition. Flavonoids that had a high degree of hydroxylation and molecular planarity gave good inhibition of RCM-κ-CN fibril formation. IC50 values were between 10- and 200-fold higher with RCM-κ-CN …
The Dissociated Form Of Kappa-Casein Is The Precursor To Its Amyloid Fibril Formation, Heath Ecroyd, David Thorn, Yanqin Liu, John Carver
The Dissociated Form Of Kappa-Casein Is The Precursor To Its Amyloid Fibril Formation, Heath Ecroyd, David Thorn, Yanqin Liu, John Carver
Heath Ecroyd
Bovine milk kappa-casein forms a self-associating oligomeric micelle-like species, in equilibrium with dissociated forms. In its native form, intra- and inter-molecular disulfide bonds lead to the formation of multimeric species ranging from monomers to decamers. When incubated under conditions of physiological pH and temperature, both reduced and non-reduced kappa-casein form highly structured beta-sheet amyloid fibrils. We investigated whether the precursor to kappa-casein fibril formation is a dissociated state of the protein or its oligomeric micelle-like form. We show that reduced kappa-casein is capable of forming fibrils well below its critical micelle concentration, i.e. at concentrations where only dissociated forms of …
The Two Faced Nature Of Milk Casein Proteins: Amyloid Fibril Formation And Chaperone-Like Activity, David Thorn, Heath Ecroyd, John Carver
The Two Faced Nature Of Milk Casein Proteins: Amyloid Fibril Formation And Chaperone-Like Activity, David Thorn, Heath Ecroyd, John Carver
Heath Ecroyd
Molecular chaperones are a diverse group of proteins that stabilise partially folded target proteins to prevent their misfolding, aggregation and potential precipitation under conditions of cellular stress, e.g. elevated temperature. Protein aggregation, particularly the formation of highly ordered protein aggregates termed amyloid fibrils, is of considerable research interest because of its intimate association with a wide range of debilitating diseases, including Alzheimer's, Parkinson's and Huntington's diseases and type II diabetes. In this review, we discuss the ability of the milk casein proteins to act in a chaperone-like manner. This property is of biological importance since at least two of the …
The Thioflavin T Fluorescence Assay For Amyloid Fibril Detection Can Be Biased By The Presence Of Exogenous Compounds, Sean A. Hudson, Heath Ecroyd, Tak W. Kee, John A. Carver
The Thioflavin T Fluorescence Assay For Amyloid Fibril Detection Can Be Biased By The Presence Of Exogenous Compounds, Sean A. Hudson, Heath Ecroyd, Tak W. Kee, John A. Carver
Heath Ecroyd
Thioflavin T (ThT) dye fluorescence is used regularly to quantify the formation and inhibition of amyloid fibrils in the presence of anti-amyloidogenic compounds such as polyphenols. However, in this study, it was shown, using three polyphenolics (curcumin, quercetin and resveratrol), that ThT fluorescence should be used with caution in the presence of such exogenous compounds. The strong absorptive and fluorescent properties of quercetin and curcumin were found to significantly bias the ThT fluorescence readings in both in situ real-time ThT assays and single time-point dilution ThT-type assays. The presence of curcumin at concentrations as low as 0.01 and 1 uM …
Crystallin Proteins And Amyloid Fibrils, Heath Ecroyd, John A. Carver
Crystallin Proteins And Amyloid Fibrils, Heath Ecroyd, John A. Carver
Heath Ecroyd
Improper protein folding (misfolding) can lead to the formation of disordered (amorphous) or ordered (amyloid fibril) aggregates. The major lens protein, alpha-crystallin, is a member of the small heat-shock protein (sHsp) family of intracellular molecular chaperone proteins that prevent protein aggregation. Whilst the chaperone activity of sHsps against amorphously aggregating proteins has been well studied, its action against fibril-forming proteins has received less attention despite the presence of sHsps in deposits found in fibril-associated diseases (e.g. Alzheimer's and Parkinson's). In this review, the literature on the interaction of alpha B-crystallin and other sHsps with fibril-forming proteins is summarized. In particular, …
Amyloid Fibril Formation By Bovine Milk Alpha(S2)-Casein Occurs Under Physiological Conditions Yet Is Prevented By Its Natural Counterpart, Alpha(S1)-Casein, David Thorn, Heath Ecroyd, M Sunde, Stephen Poon, John Carver
Amyloid Fibril Formation By Bovine Milk Alpha(S2)-Casein Occurs Under Physiological Conditions Yet Is Prevented By Its Natural Counterpart, Alpha(S1)-Casein, David Thorn, Heath Ecroyd, M Sunde, Stephen Poon, John Carver
Heath Ecroyd
The calcified proteinaceous deposits, or corpora amylacea, of bovine mammary tissue often comprise a network of amyloid fibrils, the origins of which have not been fully elucidated. Here, we demonstrate by transmission electron microscopy, dye binding assays, and X-ray fiber diffraction that bovine milk alpha(s2)-casein, a protein synthesized and secreted by mammary epithelial cells, readily forms fibrils in vitro. As a component of whole alpha(s)-casein, alpha(s2)-casein was separated from alpha(s1)-casein under nonreducing conditions via cation-exchange chromatography. Upon incubation at neutral pH and 37 degrees C, the spherical particles typical of alpha(s2)-casein rapidly converted to twisted, ribbon-like fibrils similar to 12 …
Alphab-Crystallin Inhibits The Cell Toxicity Associated With Amyloid Fibril Formation By Kappa-Casein And The Amyloid-Beta Peptide, Francis C. Dehle, Heath Ecroyd, Ian F. Musgrave, John A. Carver
Alphab-Crystallin Inhibits The Cell Toxicity Associated With Amyloid Fibril Formation By Kappa-Casein And The Amyloid-Beta Peptide, Francis C. Dehle, Heath Ecroyd, Ian F. Musgrave, John A. Carver
Heath Ecroyd
Amyloid fibril formation is associated with diseases such as Alzheimer’s, Parkinson’s, and prion diseases. Inhibition of amyloid fibril formation by molecular chaperone proteins, such as the small heat-shock protein αB-crystallin, may play a protective role in preventing the toxicity associated with this form of protein misfolding. Reduced and carboxymethylated κ-casein (RCMκ-CN), a protein derived from milk, readily and reproducibly forms fibrils at physiological temperature and pH. We investigated the toxicity of fibril formation by RCMκ-CN using neuronal model PC12 cells and determined whether the inhibition of fibril formation altered its cell toxicity. To resolve ambiguities in the literature, we also …
The Interaction Of Alphab-Crystallin With Mature Alpha-Synuclein Amyloid Fibrils Inhibits Their Elongation, Christopher A. Waudby, Tuomas P. J Knowles, Glyn L. Devlin, Jeremy N. Skepper, Heath Ecroyd, John A. Carver, Mark E. Welland, John Christodoulou, Christopher M. Dobson, Sarah Meehan
The Interaction Of Alphab-Crystallin With Mature Alpha-Synuclein Amyloid Fibrils Inhibits Their Elongation, Christopher A. Waudby, Tuomas P. J Knowles, Glyn L. Devlin, Jeremy N. Skepper, Heath Ecroyd, John A. Carver, Mark E. Welland, John Christodoulou, Christopher M. Dobson, Sarah Meehan
Heath Ecroyd
alphaB-Crystallin is a small heat-shock protein (sHsp) that is colocalized with alpha-synuclein (alphaSyn) in Lewy bodies—the pathological hallmarks of Parkinson's disease—and is an inhibitor of alphaSyn amyloid fibril formation in an ATP-independent manner in vitro. We have investigated the mechanism underlying the inhibitory action of sHsps, and here we establish, by means of a variety of biophysical techniques including immunogold labeling and nuclear magnetic resonance spectroscopy, that alphaB-crystallin interacts with alphaSyn, binding along the length of mature amyloid fibrils. By measurement of seeded fibril elongation kinetics, both in solution and on a surface using a quartz crystal microbalance, this binding …
Wild Type And Tangier Disease Abca1 Mutants Modulate Cellular Amyloid-Beta Production Independent Of Cholesterol Efflux Activity, Kim S. Woojin, Andrew F. Hill, Michael L. Fitzgerald, Mason W. Freeman, Genevieve Evin, Brett Garner
Wild Type And Tangier Disease Abca1 Mutants Modulate Cellular Amyloid-Beta Production Independent Of Cholesterol Efflux Activity, Kim S. Woojin, Andrew F. Hill, Michael L. Fitzgerald, Mason W. Freeman, Genevieve Evin, Brett Garner
Faculty of Science - Papers (Archive)
Cerebral amyloid-β (Aβ) deposition is a critical feature of Alzheimer’s disease. Aβ is derived from the amyloid-β protein precursor (AβPP) via two sequential cleavages that are mediated by β-secretase and the γ-secretase complex. Such amyloidogenic AβPP processing occurs in lipid raft microdomains of cell membranes and it is thought that modulating the distribution of lipids in rafts may regulate AβPP processing and Aβ production. Certain ATP-binding cassette (ABC) transporters regulate lipid transport across cell membranes and, as recent studies reveal, within membrane microdomains. ABCA1 also regulates Aβ metabolism in the brain although its direct impact on AβPP remains an open …
Binding Of The Molecular Chaperone Alphab-Crystallin To Abeta Amyloid Fibrils Inhibits Fibril Elongation, Sarah L. Shammas, Christopher A. Waudby, Shuyu Wang, Alexander K. Buell, Tuomas P. Knowles, Heath W. Ecroyd, Mark E. Welland, John A. Carver, Christopher M. Dobson, Sarah Meehan
Binding Of The Molecular Chaperone Alphab-Crystallin To Abeta Amyloid Fibrils Inhibits Fibril Elongation, Sarah L. Shammas, Christopher A. Waudby, Shuyu Wang, Alexander K. Buell, Tuomas P. Knowles, Heath W. Ecroyd, Mark E. Welland, John A. Carver, Christopher M. Dobson, Sarah Meehan
Faculty of Science - Papers (Archive)
The molecular chaperone αB-crystallin is a small heat-shock protein that is upregulated in response to a multitude of stress stimuli, and is found colocalized with Aβ amyloid fibrils in the extracellular plaques that are characteristic of Alzheimer's disease. We investigated whether this archetypical small heat-shock protein has the ability to interact with Aβ fibrils in vitro. We find that αB-crystallin binds to wild-type Aβ42 fibrils with micromolar affinity, and also binds to fibrils formed from the E22G Arctic mutation of Aβ42. Immunoelectron microscopy confirms that binding occurs along the entire length …