Ubiquitin-Proteasome System

Ubiquitin-Proteasome System refers to the primary cellular pathway controlling regulated protein degradation through ubiquitin tagging followed by proteasomal breakdown. This system maintains protein quality control by eliminating misfolded, damaged, or unnecessary proteins, thereby regulating cellular homeostasis, cell cycle progression, immune responses, and stress adaptation. Proteins marked with polyubiquitin chains are recognised by the 26S proteasome, which unfolds and degrades substrates into peptides while recycling ubiquitin molecules.

The pharmaceutical industry targets the ubiquitin-proteasome system in oncology and immunology, with proteasome inhibitors such as bortezomib demonstrating major clinical success in multiple myeloma. Drug discovery also explores upstream regulators including E3 ligases and deubiquitinating enzymes to achieve more selective modulation of protein turnover. Immunotherapy benefits from proteasome biology because antigen presentation depends on proteasomal peptide generation for MHC class I display. Toxicity considerations arise because broad proteasome inhibition affects many cellular functions, requiring careful dosing and patient monitoring. As targeted protein degradation approaches mature and selective pathway modulation becomes feasible, the ubiquitin-proteasome system continues shaping therapeutic innovation and mechanistic understanding across multiple disease areas.