Abstract The ubiquitin-proteasome system (UPS) is the preeminent proteolytic system in eukaryotes. While soluble nucleocytosolic proteins are readily accessed by the UPS, organelle-localised proteins present major, membrane-related accessibility challenges. Cells overcome this problem by employing the conserved AAA+ ATPase Cdc48 to extract organellar proteins to the cytosol, thereby enabling proteasomal degradation. Major Cdc48-dependent proteolytic systems exist at the endoplasmic reticulum, mitochondria and chloroplasts, and are uniquely adapted to deliver protein homeostasis within the respective organelles. We provide a focused comparison of these systems, analysing similarities and differences between them. Better understanding of underlying principles has important implications spanning human health and agriculture.
Lau et al. (2026) studied this question.