Proteasome subunit beta type-5 (PSMB5) and Proteasome subunit beta type-1 (PSMB6) (PSMB5 and PSMB6)

The 26S proteasome is a large, multi-subunit protease complex that serves as the primary machinery for regulated protein degradation within eukaryotic cells (UniProt: P28074). The 20S core particle of this complex contains the catalytic sites, specifically the beta 5 (PSMB5) and beta 1 (PSMB6) subunits, which possess chymotrypsin-like and caspase-like activities, respectively (UniProt: P28066). These subunits are critical for the degradation of polyubiquitinated proteins involved in cell cycle progression, DNA repair, and apoptosis (PubMed: 28211448). In many cancers, particularly multiple myeloma, cells become highly dependent on proteasome activity to manage the high volume of misfolded proteins produced. Therapeutic agents like bortezomib and carfilzomib target these subunits to inhibit their proteolytic function, causing an accumulation of toxic proteins and triggering the unfolded protein response (StatPearls: NBK542311). This targeted disruption effectively induces programmed cell death in malignant cells while sparing some normal cellular functions. However, inhibition of these subunits can lead to significant side effects such as peripheral neuropathy and hematologic toxicities (PubMed: 21685460).

Other names

20S proteasome beta 5 and beta 1 subunitsPSMB5PSMB6Chymotrypsin-like and caspase-like catalytic subunits of the 20S proteasomeMulticatalytic endopeptidase complex subunits

Inhibition of the chymotrypsin-like (beta 5) and caspase-like (beta 1) proteolytic activities of the 20S core of the 26S proteasome, leading to the accumulation of ubiquitinated proteins and induction of apoptosis.