# Proteasome (PSMB5)

Source: https://onco.cc/targets/proteasome/  
OnCo record `proteasome` (Target). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The cell's protein shredder. Myeloma cells make huge amounts of antibody protein and depend on the proteasome to clear the waste, so blocking it kills them.

## Summary

The 26S proteasome degrades ubiquitin-tagged proteins, and its chymotrypsin-like activity sits in the PSMB5 subunit that bortezomib and carfilzomib bind. Plasma cells, and myeloma cells in particular, secrete immunoglobulin at a rate that overloads protein quality control, so proteasome inhibition triggers a terminal unfolded protein response and blocks NF-kB signalling. Bortezomib was approved for myeloma in 2003 and carfilzomib in 2012; peripheral neuropathy is the class toxicity of bortezomib and cardiovascular events of carfilzomib.

## Fields

- Kind: Target
- Last checked: 2026-09-04
- Symbol: PSMB5
- Class: enzyme
- Biology: Multi-subunit protease complex that degrades ubiquitinated proteins; PSMB5 carries the chymotrypsin-like catalytic activity targeted by approved inhibitors.
- Where found: Multiple myeloma; Mantle cell lymphoma

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Proteasome
- UniProt P28074: PSMB5: https://www.uniprot.org/uniprotkb/P28074/entry

## Connected records

- cancers: [Mantle cell lymphoma](https://onco.cc/cancers/mantle-cell-lymphoma/), [Multiple myeloma](https://onco.cc/cancers/multiple-myeloma/), [Newly diagnosed multiple myeloma, transplant-eligible](https://onco.cc/cancers/myeloma-transplant-eligible/), [Newly diagnosed multiple myeloma, transplant-ineligible](https://onco.cc/cancers/myeloma-transplant-ineligible/), [Plasma cell leukaemia](https://onco.cc/cancers/plasma-cell-leukaemia/)
- drugs: [Bortezomib](https://onco.cc/drugs/bortezomib/), [Carfilzomib](https://onco.cc/drugs/carfilzomib/)

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JSON: https://onco.cc/api/v1/entities/proteasome.json