Cellular response to beta-amyloid neurotoxicity in Alzheimer's disease and implications in new therapeutics

beta-Amyloid (A beta) is a specific pathological hallmark of Alzheimer's disease (AD). Because of its neurotoxicity, AD patients exhibit multiple brain dysfunctions. Disease-modifying therapy (DMT) is the central concept in the development of AD therapeutics today, and most DMT drugs that are currently in clinical trials are anti-A beta drugs, such as aducanumab and lecanemab. Therefore, understanding A beta's neurotoxic mechanism is crucial for A beta-targeted drug development. Despite its total length of only a few dozen amino acids, A beta is incredibly diverse. In addition to the well-known A beta(1-42), N-terminally truncated, glutaminyl cyclase (QC) catalyzed, and pyroglutamate-modified A beta (pEA beta) is also highly amyloidogenic and far more cytotoxic. The extracellular monomeric A beta(x-42) (x = 1-11) initiates the aggregation to form fibrils and plaques and causes many abnormal cellular responses through cell membrane receptors and receptor-coupled signal pathways. These signal cascades further influence many cellular metabolism-related processes, such as gene expression, cell cycle, and cell fate, and ultimately cause severe neural cell damage. However, endogenous cellular anti-A beta defense processes always accompany the A beta-induced microenvironment alterations. A beta-cleaving endopeptidases, A beta-degrading ubiquitin-proteasome system (UPS), and A beta-engulfing glial cell immune responses are all essential self-defense mechanisms that we can leverage to develop new drugs. This review discusses some of the most recent advances in understanding A beta-centric AD mechanisms and suggests prospects for promising anti-A beta strategies.