- Proteostasis, or protein homeostasis, refers to the dynamic network of cellular processes that maintain the correct concentration, conformation, localisation, and turnover of proteins. It ensures that newly synthesised proteins fold correctly, damaged or misfolded proteins are repaired or degraded, and overall protein quality is preserved throughout the life of a cell. Proteostasis is essential for cellular function, stress resistance, and organismal longevity. Disruption of proteostasis leads to the accumulation of toxic protein aggregates, contributing to ageing and numerous diseases. As such, proteostasis forms a central concept in protein quality control and modern cell biology.
- The proteostasis network consists of three major components: molecular chaperones, the ubiquitin–proteasome system (UPS), and the autophagy–lysosome pathway. Molecular chaperones assist in protein folding, prevent aggregation, and help refold misfolded proteins. They act as the first line of defence against proteotoxic stress. The UPS selectively degrades short‑lived or damaged proteins through ubiquitination and proteasomal degradation, ensuring rapid turnover and precise regulation of protein levels. The autophagy–lysosome pathway removes long‑lived proteins, aggregates, and entire organelles, providing a bulk degradation mechanism essential during nutrient deprivation and cellular stress. Together, these systems form an integrated network that preserves protein integrity.
- Proteostasis is tightly regulated by cellular stress responses. The heat‑shock response (HSR) increases chaperone production when misfolded proteins accumulate, restoring folding capacity. The unfolded protein response (UPR) in the endoplasmic reticulum detects misfolded secretory proteins and activates pathways that enhance folding, reduce protein synthesis, and promote degradation. Similarly, the mitochondrial UPR maintains proteostasis within mitochondria. These stress responses ensure that cells adapt to environmental changes and maintain protein quality under challenging conditions.
- Ageing is closely linked to proteostasis decline. As organisms age, chaperone activity decreases, proteasome efficiency diminishes, and autophagy becomes less effective. This leads to the accumulation of misfolded proteins and aggregates, contributing to age‑related diseases such as Alzheimer’s, Parkinson’s, and Huntington’s disease. Many neurodegenerative disorders are characterised by toxic protein aggregates that overwhelm the proteostasis network. Understanding how proteostasis fails during ageing provides insight into disease mechanisms and potential therapeutic strategies.
- Proteostasis is also critical in cancer biology. Tumour cells experience high levels of proteotoxic stress due to rapid proliferation and altered metabolism. To survive, they rely heavily on chaperones, UPS activity, and autophagy. As a result, components of the proteostasis network have become major therapeutic targets. Proteasome inhibitors, autophagy modulators, and chaperone inhibitors are being explored to disrupt tumour survival mechanisms. These approaches highlight the importance of proteostasis in disease treatment and biomedical research.
- Overall, proteostasis is a fundamental aspect of cellular health. Its coordinated network of folding, repair, and degradation ensures that proteins remain functional and balanced. By maintaining protein integrity, proteostasis supports cellular stability, stress resilience, and organismal longevity. Understanding proteostasis provides valuable insight into ageing, neurodegeneration, cancer, and the molecular basis of life.
