PSMB8

The proteasome is a multicatalytic proteinase complex with a highly ordered ring-shaped 20S core structure. The core structure is composed of 4 rings of 28 non-identical subunits; 2 rings are composed of 7 alpha subunits and 2 rings are composed of 7 beta subunits. Proteasomes are distributed throughout eukaryotic cells at a high concentration and cleave peptides in an ATP/ubiquitin-dependent process in a non-lysosomal pathway. An essential function of a modified proteasome, the immunoproteasome, is the processing of class I MHC peptides. This gene encodes a member of the proteasome B-type family, also known as the T1B family, that is a 20S core beta subunit. This gene is located in the class II region of the MHC (major histocompatibility complex). Expression of this gene is induced by gamma interferon and this gene product replaces catalytic subunit 3 (proteasome beta 5 subunit) in the immunoproteasome. Proteolytic processing is required to generate a mature subunit. Two alternative transcripts encoding two isoforms have been identified; both isoforms are processed to yield the same mature subunit. [provided by RefSeq]

Full Name

proteasome (prosome, macropain) subunit, beta type, 8 (large multifunctional peptidase 7)

Function

The proteasome is a multicatalytic proteinase complex which is characterized by its ability to cleave peptides with Arg, Phe, Tyr, Leu, and Glu adjacent to the leaving group at neutral or slightly basic pH. The proteasome has an ATP-dependent proteolytic activity. This subunit is involved in antigen processing to generate class I binding peptides. Replacement of PSMB5 by PSMB8 increases the capacity of the immunoproteasome to cleave model peptides after hydrophobic and basic residues. Involved in the generation of spliced peptides resulting from the ligation of two separate proteasomal cleavage products that are not contiguous in the parental protein (PubMed:27049119).
Acts as a major component of interferon gamma-induced sensitivity. Plays a key role in apoptosis via the degradation of the apoptotic inhibitor MCL1. May be involved in the inflammatory response pathway. In cancer cells, substitution of isoform 1 (E2) by isoform 2 (E1) results in immunoproteasome deficiency. Required for the differentiation of preadipocytes into adipocytes.

Biological Process

Antigen processing and presentationIEA:Ensembl
Fat cell differentiationManual Assertion Based On ExperimentIMP:UniProtKB
Proteasomal protein catabolic processManual Assertion Based On ExperimentIBA:GO_Central
Regulation of endopeptidase activityManual Assertion Based On ExperimentIMP:UniProtKB

Cellular Location

Cytoplasm
Nucleus

Involvement in disease

Proteasome-associated autoinflammatory syndrome 1 (PRAAS1):
An autosomal recessive autoinflammatory disorder characterized by early childhood onset of recurrent fever, joint stiffness and severe contractures of the hands and feet, and erythematous skin lesions with subsequent development of lipodystrophy and laboratory evidence of immune dysregulation. Accompanying features may include muscle weakness and atrophy, hepatosplenomegaly, and microcytic anemia.

PTM

Autocleaved. The resulting N-terminal Thr residue of the mature subunit is responsible for the nucleophile proteolytic activity.