|CD8a||CD8α - MAL, p32, Leu2, OKT8, LeuT, LyT2, T8, Ly3, LyT3, Leu2|
|Molecule Type||Antigen Expression||Molecular Weight|
Min / Max
|Lineage Restricted Molecule|
Type 1 glycoprotein
|30 / 30|
32 / 32
34 / 34
68 / 68
|CD8α occurs as a homodimer or a heterodimer associated with CD8β. The heterodimer is the predominant form in peripheral blood. CD8 is expressed on thymocyte subsets and T cells specific for antigen presented with MHC class I (cytotoxic T cells), some γ/δ T cells and NK cells and approximately 1/3rd of peripheral blood T cells in humans. α/β T cells express the CD8 heterodimer whereas γ/δ cells express the CD8α homodimer.|
|MOLECULAR FAMILY NAME: Belongs to the immunoglobulin supergene family.|
CD8α and CD8β are a single-pass type-1 glycoproteins. They contain an extracellular domain which contains an Ig-like V-type domain which is separated from transmembrane sequences by hinge domain, a transmembrane domain and the cytoplasmic domain of CD8α contains a binding motif for tyrosine kinase Lck. CD8α is a disulfide-linked homodimer and heterodimer while CD8β is a heterodimer and cannot homodimerize.
Alterantive splicing yields 2 different isoforms for CD8α and 5 different isoforms for CD8β.
POST-TRANSLATIONAL MODIFICATION : No information.
|LIGANDS AND MOLECULES ASSOCIATED WITH CD8α & CD8β|
The IgSF domain of CD8a binds to the a3 domain of MHC class I. Like CD4, a CXCP motif in the cytoplasmic domain of CD8a mediates binding to the tyrosine kinase Lck.
|CD8α & CD8β acts as a coreceptor with MHC class I-restricted TCRs in antigen recognition. On T cells, it binds to MHC class I on an antigen presenting enhancing the cognate interaction between the T cell receptor complex and the antigenic peptide/MHC class I complex. Anti-antibodies inhibit cytotoxic T lymphocytes and may play a role in in the process of T cell-mediated killing. Analysis in mice lacking CD8a or CD8b show that the coreceptor function of CD8 is important for selection of MHC class I-restricted CD8+ T cells during development.|
BIOCHEMICAL ACTIVITY : No information.
DISEASE RELEVANCE AND FUNCTION OF CD8α & CD8β IN INTACT ANIMAL
Defects in CD8α are a cause of familial deficiency leading to recurrent bacterial infections.
Database accession numbers
Revised June 25, 2008