Proteasome subunit beta type-3

PSMB3 (proteasome subunit beta type-3) is a non-catalytic structural component of the 20S core proteasome complex (UniProt: P49720). It participates in proteolytic degradation of intracellular proteins, functioning both as part of the 26S proteasome (ATP-dependent degradation of ubiquitinated proteins) and in association with regulatory particles like PA200 or PA28 for ubiquitin-independent proteolysis. These activities are essential for maintaining protein homeostasis by removing misfolded, damaged, or obsolete proteins.

The proteasome is widely expressed across tissues and plays fundamental roles in cellular protein quality control and regulatory protein turnover. Dysfunction of proteasomal degradation pathways is implicated in neurodegenerative disease pathogenesis through accumulation of toxic protein aggregates.

PSMB3 is downregulated in Alzheimer's disease brain tissue compared to age-matched controls (Chaparral AD proteomics), with a mean log2 fold-change of −0.49 across post-mortem samples analyzed by TMT-labeled proteomics. This reduction in proteasomal capacity may contribute to impaired clearance of misfolded proteins, including amyloid-beta and tau aggregates, consistent with protein homeostasis dysfunction observed in AD pathology.