CD25 Tac antigen, IL-2Rα chain
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
Type 1 glycoprotein
B Cell
T Cell
Monocyte
Oligodendrocyte
Thymocyte
Macrophage
NK Cell
Myeloid Cell
Lymphoid Cell
55 / 55

Expression
The IL-2R is expressed on activated cells including T and B cells and monocytes.  The CD25 subunit of the human IL-2R is also present on a subset of thymocytes, HTLV-1 transformed T and B cells, EBV transformed B cells, myeloid precursors and oligodendrocytes.  IL-2 induces the expression of the CD25 subunit on NK cells.  CD25 is expressed, typically at high levels, on PHA-stimulated T cells, on B cells stimulated with anti-IgM antibody, on monocytes/macrophages stimulated with LPS and highly expressed on HTLV-1-transformed T cell lines.  CD25 is proteolytically released from lymphoid cells and is found in serum but is detected at a low level in a subset of resting T cells

  

Structure
MOLECULAR FAMILY NAME: Belongs to the cytokine receptor family.

CD25 is a single-pass type-1 a chain 272 aa glycoprotein.  It contains an extracellular domain which contains 2 complement control protein (CCP) domains and an extensively N- and O-linked carbohydrate glycosylation sites, a transmembrane domain and a short 13 aa cytoplasmic domain.  The IL-15R a chain is structurally related to CD25, the IL-2Rα chain.  Proteolytic cleavage of membrane-bound CD25 generates a soluble form present in human serum.  The functional high affinity of IL-2R with kDa = 10 pM is composed of a non-covalently associated CD25/CD122/CD132 (IL-2Rα/IL-2Rβ/IL-2Rγ) heterotrimer.  The isolated CD25 subunit constitutes a low-affinity IL-2R with kDa = 10 nM.  

MOLECULAR MASS
Cell type Unreduced Reduced
Lymphocytes 55 kDa 55 kDa

POST-TRANSCRIPTIONAL MODIFICATION

Alternatively spliced CD25 mRNA have been isolated but the significance is presently unknown.

POST TRANSLATIONAL MODIFICATION

CD25 is highly N-glycosylated and O-glycosylated.  Soluble CD25 is produced from CD25 by proteolytic cleavage.


Ligands
CD25 is the α-chain of a three-chain receptor for IL-2.  CD25 does bind IL-2 by itself but with low affinity.

LIGANDS AND MOLECULES ASSOCIATED WITH CD25
Molecule Comment
IL-2 (interleukin-2)
CD122 (IL-2Rb) High-affinity IL-2 receptor consists of CD25, CD122 and CD132
CD132 (IL-2Rg) High-affinity IL-2 receptor consists of CD25, CD122 and CD132

 

Function
CD25 contains an α-chain which is a low-affinity IL-2 receptor and a β-chain which is a medium-affinity receptor and an activation marker which induces the activation and proliferation of T cells, thymocytes, NK cells, B cells and macrophages.  By noncovalently associating with CD122 and CD132 (which can also combine with CD124 and CD217 to form the IL-4 and IL-7 receptors), it forms the high affinity IL-2 receptor complex.  CD4+CD25+ regulatory T cells seem to regulate other T cells and play a role in limiting inflammatory responses and preventing autoimmunity as knockout mice develop autoimmune diseases.  CD25 also associates with β and γ chains to form high affinity with IL-2R.  CD25 plays a role in T cell mediated immune response and is phosphorylated on Ser and Thr residues.  CD25 is membrane-bound and soluble and is used to monitor cell activation in immune response. 

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD25 IN INTACT ANIMAL

In 4 lines of human adult T cell lymphoma leukemia origin, 3 CD25 subunits are compartmented together with HLA glycoproteins and CD48 molecules in the plasma membrane.  

Comments
MOLECULAR INTERACTIONS-
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD25
 
Molecule Type Comment
Stat5 Transcription factor binds an IL-2 responsive element in CD25 promoter
Elf-1 Transcription factor binds an IL-2 responsive element in CD25 promoter
HGG-I(Y) Transcription factor binds an IL-2 responsive element in CD25 promoter
GATA Transcription factor binds an IL-2 responsive element in CD25 promoter
Tax from HTLV-1

SUBSTRATE: No information.

ENZYMES WHICH MODIFY CD25: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene3559P01589
MouseA01857P01590K02891
RatA46535P26897M55049
Antibodies
B1.49.9   View Reactivity
CACT108A   View Reactivity
CACT116A   View Reactivity
CACT260A   View Reactivity
GB112A   View Reactivity
K231.3B2   View Reactivity
KE1alpha1   View Reactivity
LCTB2A   View Reactivity
M-A251   View Reactivity
PGBL25A   View Reactivity

Revised June 25, 2008


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