Protein Aggregation and Disaggregation: Insights from In Vivo Studies

Description

This lecture by Helen Saibil delves into the mechanisms of protein aggregation and disaggregation in vivo and in vitro, focusing on the case of huntingtin protein in Huntington's Disease. The presentation covers the formation of different types of aggregates, the role of polyQ repeats in toxicity, and the impact of aggregation on disease progression. Saibil also discusses the importance of cytoplasmic aggregates in disease severity, the heterogeneity of mutant huntingtin aggregates, and the machinery involved in reversing aggregation. Through various microscopy techniques, the lecture reveals the unexpected cellular pathways of huntingtin aggregation and the machinery responsible for disassembling amyloid fibrils.

Official source

https://mediaspace.epfl.ch/media/0_g6swqzeo

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Amyloid beta

Amyloid beta (Aβ or Abeta) denotes peptides of 36–43 amino acids that are the main component of the amyloid plaques found in the brains of people with Alzheimer's disease. The peptides derive from the amyloid-beta precursor protein (APP), which is cleaved by beta secretase and gamma secretase to yield Aβ in a cholesterol-dependent process and substrate presentation. Aβ molecules can aggregate to form flexible soluble oligomers which may exist in several forms.

Amyloidosis

Amyloidosis is a group of diseases in which abnormal proteins, known as amyloid fibrils, build up in tissue. There are several non-specific and vague signs and symptoms associated with amyloidosis. These include fatigue, peripheral edema, weight loss, shortness of breath, palpitations, and feeling faint with standing. In AL amyloidosis, specific indicators can include enlargement of the tongue and periorbital purpura.

Protein folding

Protein folding is the physical process where a protein chain is translated into its native three-dimensional structure, typically a "folded" conformation, by which the protein becomes biologically functional. Via an expeditious and reproducible process, a polypeptide folds into its characteristic three-dimensional structure from a random coil. Each protein exists first as an unfolded polypeptide or random coil after being translated from a sequence of mRNA into a linear chain of amino acids.

Tau protein

The tau proteins (abbreviated from tubulin associated unit) are a group of six highly soluble protein isoforms produced by alternative splicing from the gene MAPT (microtubule-associated protein tau). They have roles primarily in maintaining the stability of microtubules in axons and are abundant in the neurons of the central nervous system (CNS), where the cerebral cortex has the highest abundance. They are less common elsewhere but are also expressed at very low levels in CNS astrocytes and oligodendrocytes.

Cellular differentiation

Cellular differentiation is the process in which a stem cell changes from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and create fully differentiated daughter cells during tissue repair and during normal cell turnover.