Immunoproteasome subunit beta-5i (PSMB8)

The immunoproteasome is a specialized isoform of the 26S proteasome, primarily expressed in hematopoietic cells or induced in other tissues by inflammatory cytokines such as interferon-gamma [UniProt: P28062]. It is defined by the incorporation of three unique catalytic subunits—beta-1i (LMP2), beta-2i (MECL-1), and beta-5i (LMP7)—which replace their constitutive counterparts to alter the proteolytic specificity of the complex [PubMed: 29438138]. These subunits are optimized to generate peptides with hydrophobic C-termini, which are preferred for loading onto MHC class I molecules, thereby facilitating effective CD8+ T-cell immune surveillance [UniProt: P28065]. The beta-5i subunit, encoded by the PSMB8 gene, is the most prominent therapeutic target due to its role in regulating the production of pro-inflammatory cytokines like IL-6 and TNF-alpha [PubMed: 31434684]. Dysregulation of the immunoproteasome is implicated in various autoimmune conditions, including systemic lupus erythematosus and rheumatoid arthritis, as well as autoinflammatory disorders like CANDLE syndrome [NIH: GARD]. Therapeutic strategies involve the use of selective inhibitors, such as zetomipzomib, which target the immunoproteasome subunits to dampen pathological immune responses while minimizing the systemic toxicity associated with non-selective proteasome inhibition [Kezar Life Sciences].

Other names

LMP7Beta-5iProteasome subunit beta type-8RING10PSMB9LMP2PSMB10MECL-1Immunoproteasome catalytic subunits

Selective inhibition of the chymotrypsin-like activity of the immunoproteasome catalytic subunits, particularly beta-5i (LMP7), to modulate cytokine signaling and antigen presentation.