62 research outputs found
Early events in insulin fibrillization studied by time-lapse atomic force microscopy
The importance of understanding the mechanism of protein aggregation into
insoluble amyloid fibrils relies not only on its medical consequences, but also
on its more basic properties of self--organization. The discovery that a large
number of uncorrelated proteins can form, under proper conditions, structurally
similar fibrils has suggested that the underlying mechanism is a general
feature of polypeptide chains. In the present work, we address the early events
preceeding amyloid fibril formation in solutions of zinc--free human insulin
incubated at low pH and high temperature. Aside from being a easy--to--handle
model for protein fibrillation, subcutaneous aggregation of insulin after
injection is a nuisance which affects patients with diabetes. Here, we show by
time--lapse atomic force microscopy (AFM) that a steady-state distribution of
protein oligomers with an exponential tail is reached within few minutes after
heating. This metastable phase lasts for few hours until aggregation into
fibrils suddenly occurs. A theoretical explanation of the oligomer
pre--fibrillar distribution is given in terms of a simple
coagulation--evaporation kinetic model, in which concentration plays the role
of a critical parameter. Due to high resolution and sensitivity of AFM
technique, the observation of a long-lasting latency time should be considered
an actual feature of the aggregation process, and not simply ascribed to
instrumental inefficency. These experimental facts, along with the kinetic
model used, claim for a critical role of thermal concentration fluctuations in
the process of fibril nucleation
Changes in extracellular space size and geometry in APP23 transgenic mice: A model of Alzheimer's disease
The elusive nature and diagnostics of misfolded Aβ oligomers.
Amyloid-beta (Aβ) peptide oligomers are believed to be the causative agents of Alzheimer's disease (AD). Though post-mortem examination shows that insoluble fibrils are deposited in the brains of AD patients in the form of intracellular (tangles) and extracellular (plaques) deposits, it has been observed that cognitive impairment is linked to synaptic dysfunction in the stages of the illness well before the appearance of these mature deposits. Increasing evidence suggests that the most toxic forms of Aβ are soluble low-oligomer ligands whose amounts better correlate with the extent of cognitive loss in patients than the amounts of fibrillar insoluble forms. Therefore, these ligands hold the key to a better understanding of AD prompting the search for clearer correlations between their structure and toxicity. The importance of such correlations and their diagnostic value for the early diagnosis of AD is discussed here with a particular emphasis on the transient nature and structural plasticity of misfolded Aβ oligomers
Unraveling the Early Events of Amyloid-β Protein (Aβ) Aggregation: Techniques for the Determination of Aβ Aggregate Size
The aggregation of proteins into insoluble amyloid fibrils coincides with the onset of numerous diseases. An array of techniques is available to study the different stages of the amyloid aggregation process. Recently, emphasis has been placed upon the analysis of oligomeric amyloid species, which have been hypothesized to play a key role in disease progression. This paper reviews techniques utilized to study aggregation of the amyloid-β protein (Aβ) associated with Alzheimer’s disease. In particular, the review focuses on techniques that provide information about the size or quantity of oligomeric Aβ species formed during the early stages of aggregation, including native-PAGE, SDS-PAGE, Western blotting, capillary electrophoresis, mass spectrometry, fluorescence correlation spectroscopy, light scattering, size exclusion chromatography, centrifugation, enzyme-linked immunosorbent assay, and dot blotting
Spontaneous in Vitro Formation of Supramolecular β-Amyloid Structures, “βamy Balls”, by β-Amyloid 1−40 Peptide †
Long-term treatment with memantine prevents behavioral deficits in a mouse model of sporadic alzheimer
Long-term memantine treatment prevents behaviour deficits in a mouse model of sporadic Alzheimer's disease
Long-term memantine treatment prevents behavioral deficits in a mouse model of sporadic Alzheimer's disease
Memantine reverses in vivo tau hyperphosphorylation and a behavioural deficit in a mouse model of Alzheimer's disease
Long-term memantine treatment prevents behavioral deficits in a mouse model of Alzheimer's disease
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