CD8a CD8α - MAL, p32, Leu2, OKT8, LeuT, LyT2, T8,  Ly3, LyT3, Leu2
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
Type 1 glycoprotein
NK Cell
T Cell
Thymocyte
Blood Cell
30 / 30
32 / 32
34 / 34
68 / 68

Expression
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.

Structure
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.

MOLECULAR MASS
Cell Type Unreduced Reduced
CD8a 68 kDa plus higher multimers 32-34 kDa
CD8b 68 kDa plus higher multimers 30-32 kDa

POST-TRANSCRIPTIONAL MODIFICATION

Alterantive splicing yields 2 different isoforms for CD8α and 5 different isoforms for CD8β.

POST-TRANSLATIONAL MODIFICATION
: No information.


Ligands
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.



Function
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.


Comments


MOLECULAR INTERACTIONS-
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD8α & CD8β : No information.

SUBSTRATES
: No information.

ENZYMES WHICH MODIFY CD8α & CD8β
 : No information.



Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 925P10732
HumanEntrezgene 926P10966
MouseA01998P01731M12825
MouseA27619P10300X07698
RatA24637P07725X03015
RatA24184P05541X04310
Antibodies
11-39   View Reactivity
12C6   View Reactivity
25-1B   View Reactivity
25-2A   View Reactivity
2ST8.5H7   View Reactivity
38.65   View Reactivity
4B11   View Reactivity
73/6.9.1   View Reactivity
76-2-11   View Reactivity
7C2B   View Reactivity
B9.11   View Reactivity
BAQ111A   View Reactivity
BAT82A   View Reactivity
CA15.4G2   View Reactivity
CA9.JD3   View Reactivity
CACT80C   View Reactivity
CACT88A   View Reactivity
CADO46A   View Reactivity
CC58   View Reactivity
CC63   View Reactivity
CT6   View Reactivity
CVS21   View Reactivity
FE1.10E9   View Reactivity
FE5.4D2   View Reactivity
G42-8   View Reactivity
HIT8a   View Reactivity
HT14A   View Reactivity
ISC16A   View Reactivity
ISC27A   View Reactivity
ISC29E   View Reactivity
ISC38A   View Reactivity
LT5A   View Reactivity
LT8   View Reactivity
MIL12   View Reactivity
PG164A   View Reactivity
PT36B   View Reactivity
PT81B   View Reactivity
RPA-T8   View Reactivity
ST8   View Reactivity
TH82A   View Reactivity
vpg9   View Reactivity
VPM31   View Reactivity
YCATE55.9   View Reactivity
YTC141.1HL   View Reactivity
YTC182.20   View Reactivity

Revised June 25, 2008


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