PSMB9

Proteasome subunit beta type-9
Identifiers
Symbol	?
NCBI gene	5698
HGNC	9530
OMIM	177045
RefSeq	NM_002800
UniProt	P28065
Search for Structures Swiss-model Domains InterPro

Proteasome subunit beta type-9 (PSMB9) is a protein that in humans is encoded by the PSMB9 gene. This protein is a component of the proteasome, a large protein complex responsible for degrading ubiquitinated proteins, which is crucial for maintaining cellular protein homeostasis.

Structure

PSMB9 is a part of the 20S core of the proteasome, specifically one of the beta subunits. The proteasome is a multi-catalytic proteinase complex with a highly ordered ring-shaped 20S core structure. The core is composed of 28 subunits arranged in four stacked rings, resulting in a barrel-shaped structure. The two outer rings are each composed of seven alpha subunits, and the two inner rings are each composed of seven beta subunits, including PSMB9.

Function

PSMB9 plays a critical role in the immunoproteasome, a specialized form of the proteasome that is induced by interferon-gamma and is involved in the processing of antigenic peptides for presentation by MHC class I molecules. This process is essential for the immune system to recognize and eliminate infected or cancerous cells.

The immunoproteasome differs from the standard proteasome by the replacement of certain catalytic subunits, including PSMB9, which is also known as LMP2 (low molecular mass polypeptide 2). The incorporation of PSMB9 into the proteasome alters its cleavage specificity, enhancing the production of peptides that are optimal for MHC class I binding.

Clinical Significance

Mutations or dysregulation of PSMB9 have been implicated in various diseases, including autoimmune disorders and certain types of cancer. The altered function of the immunoproteasome can affect antigen processing and presentation, potentially leading to immune evasion by tumors or inappropriate immune responses in autoimmune diseases.

Research and Therapeutic Implications

The study of PSMB9 and the immunoproteasome is an active area of research, with implications for the development of novel therapeutic strategies. Inhibitors targeting the immunoproteasome are being explored for their potential to modulate immune responses in diseases such as multiple myeloma and autoimmune disorders.

Also see

• Proteasome
• Immunoproteasome
• MHC class I
• Ubiquitin-proteasome system
• Interferon-gamma