Protein Homeostasis and Mitochondrial Quality Control in Neurodegeneration.

Quality control (QC) processes include a network of cellular pathways that prevent the accumulation of toxic aggregates by repairing, recycling, and/or eliminating defective components, including mitochondria. Among these pathways are the proteostasis network, which regulates the proteome, and mitochondrial quality control (MQC) mechanisms, which maintain mitochondrial number and integrity. QC relies on a hierarchically and spatially integrated regulatory axis rather than individual parallel units. Such systems coordinate mitochondrial biogenesis, dynamics, and autophagic recycling with proteostasis to ensure the maintenance of high-quality mitochondria and bioenergetically efficient cells. Neurons, post-mitotic cells with high energy demands, depend heavily on these mechanisms and on the spatial coordination of MQC. Here, we discuss how failure of this integrated QC axis, rather than dysfunction of its individual components alone, can drive neuronal decline and contribute to the neurodegeneration.