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[Home] [Cytokines] [Description] [Features & Philosophy] [Comparison] |
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[Class I] [Class II] [What is a Chemokine] [Chemokine Receptor Family] |
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CLASS I CYTOKINE RECEPTOR FAMILY (HEMATOPOIETIN RECEPTOR FAMILY) - from IMMUNOLOGY by Kuby© 1992, 1994, 1997 by W.H. Freeman and Company. Used with permission Most of the cytokine-binding receptors that function in the immune and hematopoietic systems belong to this receptor family. In addition, this family includes receptors for growth hormone and prolactin. There are conserved amino acid sequence motifs in the extracellular domain - 4 positionally conserved cysteine residues (CCCC) and a conserved sequence of Trp-Ser-X-Trp-Ser (WSXWS) where X is a nonconserved amino acid. The receptors consist of 2 polypeptide chains: a cytokine-specific subunit and a signal-transducing subunit which is usually not specific for the cytokine. In a few cases these receptors are trimers. The signal transducing subunit is required for high affinity binding of the cytokine. Class I cytokine receptors have been further divided into sub-families with all the receptors in one subfamily having an identical signal transducing subunit. This subfamily includes the receptors for IL-3, IL-5, and GM-CSF. The unique low affinity, cytokine-specific receptor is the a subunit. All three low affinity a subunits can associate noncovalently with a common signal transducing ß subunit. The resulting dimeric receptor exhibits increased affinity for the cytokine but also transduces a signal across the membrane following cytokine binding. Interestingly, IL-3, IL-5, and GM-CSF exhibit considerable redundancy in their activities. This subfamily includes the receptors for IL-6, IL-11, and IL-12. In this case a common signal transducing subunit (gp130) associates with one or two different cytokine-specific subunits. As you might expect, the cytokines that bind to receptors in this subfamily display overlapping biological activities. This subfamily includes the receptors for IL-2, IL-4, IL-7, IL-9, and IL-15. The IL-2 and IL-15 receptors are trimers, consisting of a cytokine-specific a chain and two chains - ß and g - responsible for signal transduction. The IL-2 receptor g chain is the signal transducing subunit in those members of this subfamily which are dimers. |
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[Home] [Cytokines] [Description] [Features & Philosophy] [Comparison] |
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[Class I] [Class II] [What is a Chemokine] [Chemokine Receptor Family] |
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Pathology Course Menu | Pathology | NJMed P.C. | NJMS | Search | UMDNJ |
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Please direct questions and coments to Alexander G. Izaguirre izaguial@umdnj.edu |
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