The ubiquitin-proteasome system and autophagy as guardians of the cellular proteome

Maintaining a functional proteome is essential for cellular health and organismal longevity. Disruption of proteostasis is a hallmark of aging and a central driver of diverse pathologies, including neurodegeneration, cancer, and metabolic disease. The ubiquitin-proteasome system (UPS) and autophagy represent the two principal degradative pathways safeguarding proteome integrity, particularly under conditions of stress. While historically viewed as mechanistically distinct, it is now clear that UPS and autophagy operate as an interconnected and adaptive network. This Perspective discusses three core principles that govern their coordination: (1) a shared molecular language of ubiquitin signals and shuttle proteins that determines cargo routing; (2) spatial compartmentalization through organelle-specific quality control modules and phase-separated degradation hubs; and (3) temporal regulation by stress-responsive signaling pathways that reprogram proteolytic output. Understanding this dynamic partnership not only reveals fundamental organizing principles of cellular homeostasis but also identifies new therapeutic nodes for diseases driven by proteostasis collapse.