Cytokine receptor

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A Cytokine receptor is a receptor which binds cytokines.

In recent years, the cytokine receptors have come to demand the attention of more investigators than cytokines themselves, partly because of their remarkable characteristics, and partly because a deficiency of cytokine receptors has now been directly linked to certain debilitating immunodeficiency states. In this regard, and also because the redundancy and pleiomorphism of cytokines are, in fact, a consequence of their homologous receptors, many authorities are now of the opinion that a classification of cytokine receptors would be more clinically and experimentally useful.

Classification

A classification of cytokine receptors based on their three-dimensional structure has been attempted. (It must be noted that such a classification, though seemingly cumbersome, provides with several unique perspectives for attractive pharmacotherapeutic targets.)

• Type 1 interleukin receptors, whose members have certain conserved motifs in their extracellular amino-acid domain. The IL-2 receptor belongs to this chain, whose γ-chain (common to several other cytokines) deficiency is directly responsible for the x-linked form of Severe Combined Immunodeficiency (X-SCID).
• type II cytokine receptors, whose members are receptors mainly for interferons.
• Immunoglobulin (Ig) superfamily, which are ubiquitously present throughout several cells and tissues of the vertebrate body
• Tumor necrosis factor receptor family, whose members share a cysteine-rich common extracellular binding domain, and includes several other non-cytokine ligands like CD40, CD27 and CD30, besides the ligands on which the family is named (TNF).
• Chemokine receptors, two of which acting as binding proteins for HIV (CXCR4 and CCR5). They are G protein coupled receptors.
• TGF beta receptors

Comparison

Type	Examples	Structure	Mechanism
type I cytokine receptor	Type 1 interleukin receptors Erythropoietin receptor GM-CSF receptor G-CSF receptor growth hormone receptor prolactin receptor Oncostatin M receptor Leukemia inhibitory factor receptor	Certain conserved motifs in their extracellular amino-acid domain. Connected to Janus kinase (JAK) family of tyrosine kinases	JAK phosphorylate and activate downstream proteins involved in their signal transduction pathways
type II cytokine receptor	Type II interleukin receptors interferon-alpha/beta receptor interferon-gamma receptor
Many members of the immunoglobulin superfamily	Interleukin-1 receptor CSF1 C-kit receptor Interleukin-18 receptor	Share structural homology with immunoglobulins (antibodies), cell adhesion molecules, and even some cytokines.
Tumor necrosis factor receptor family	CD27 CD30 CD40 CD120 Lymphotoxin beta receptor	cysteine-rich common extracellular binding domain
chemokine receptors	Interleukin-8 receptor CCR1 CXCR4 MCAF receptor NAP-2 receptor	Seven transmembrane helix	G protein-coupled
TGF beta receptors	TGF beta receptor 1 TGF beta receptor 2

Solubility

Cytokine receptors may be both membrane-bound and soluble. Soluble cytokine receptors are extremely common regulators of cytokine function.

See also

• STAT protein

External links

Cytokine receptors

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Last updated on Saturday March 01, 2008 at 12:38:35 PST (GMT -0800)
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