Amyloid Peptides

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Introduction

Amyloid peptide is a fragment of 39 to 43 amino acids which is cleaved by an enzymatic pathway by an amyloid precursor protein (APP) present on the cell membrane. The APP has a molecular weight of 110 to 135 kD, and the gene is located in the middle of the long arm of human chromosome 21. Amyloid peptide is secreted by cells and has a strong neurotoxic effect after aggregation and precipitation in the cell matrix. The most common subtypes of amyloid peptides in humans are Aβ₄₀ and Aβ₄₂, and under normal conditions Aβ₄₂ accounts for only one-tenth of the total amyloid peptide, but is more toxic and easier to aggregate. Amyloid peptide plays a significant role in the human nervous system. Many systemic neurodegenerative diseases are related to the pathological changes of amyloid related peptides.

Mechanism of action

Excessive expression of amyloid peptide increases neurite outgrowth and accelerates oxidative damage. Amyloid peptide can destroy calcium channels on the cell membrane and increase calcium influx, leading to intracellular calcium imbalance. Intracellular calcium overload can damage mitochondrial buffer, leading to cytotoxicity. Amyloid peptide is also able to promote the opening of cholinergic neuronal membrane potassium channels, promote K⁺ efflux and disrupt calcium homeostasis, leading to abnormal AChE expression. The abnormal expression of AChE can further enhance the neurotoxicity of amyloid peptide, leading to the decline of cholinergic neurons and hippocampal neurons.

Application of Amyloid Peptides

The deposition of amyloid peptide is not only related to degenerative diseases of neurons such as Alzheimer’s disease, but also related to the activation of a variety of antibodies including astrocytes and microglia. According to current researches, it can be seen that reducing the deposition of amyloid peptide can greatly benefit for Alzheimer’s disease. Therefore, targeting amyloid peptide is one of the best ways to prevent the occurrence and development of Alzheimer's disease.

References

1. Haass C, Hung A Y, Schlossmacher M G, et al. beta-Amyloid peptide and a 3-kDa fragment are derived by distinct cellular mechanisms[J]. Journal of Biological Chemistry, 1993, 268(5):3021-4.
2. Cheignon C, Tomas M, Bonnefont-Rousselot D, et al. Oxidative stress and the amyloid beta peptide in Alzheimer's disease[J]. Redox Biol, 2018, 14:450-464.