Protein degradation pathway

The **protein degradation pathway** encompasses several essential cellular systems responsible for dismantling and recycling proteins. The two primary mechanisms are the **ubiquitin-proteasome system**, which tags unwanted or damaged intracellular proteins with ubiquitin before their destruction by the proteasome—a large multi-subunit enzyme complex—and **autophagy**, where larger structures including organelles are engulfed by autophagosomes then degraded after fusion with lysosomes containing digestive enzymes. These processes maintain cellular health through quality control functions—removing misfolded/toxic proteins—regulating key biological events such as cell cycle progression and apoptosis, enabling nutrient recycling during stress conditions, and defending against pathogens. Dysregulation contributes significantly to diseases including cancer (by allowing accumulation/stabilization of oncogenic factors), neurodegeneration (via toxic aggregate buildup), metabolic disorders, immune dysfunctions/infections. While these pathways themselves are not direct drug targets per se, their core components—such as specific E3 ubiquitin ligases or the proteasome—are actively pursued in therapeutic development using strategies like small-molecule inhibitors or targeted degraders known as PROTACs®.

Other names

Protein catabolism pathwaysProteolytic pathwaysUbiquitin-proteasome system (UPS)Autophagy-lysosomal pathway

For drugs acting on this system generally— - Inhibition of proteolytic activity within the proteasome leads to accumulation of proteins and induction of apoptosis in cancer cells. - Recruitment/hijacking of E3 ubiquitin ligases by small molecules/protacs results in selective ubiquitination and subsequent proteasomal degradation of target proteins. - Induction/enhancement of autophagic flux for removal/degradation of aggregated/damaged proteins.