CD4 is a monomeric transmembrane glycoprotein of the Ig superfamily. In humans, the CD4 gene is encoded [2] [3] .
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It has a molecular mass of 55 kD , contains 4 extracellular domains, a transmembrane domain and a cytoplasmic site, and is a marker of T-helper cells. Acts as an αβTCR coreceptor: binding to the invariant β 2 domain of MHC class II, it is involved in the recognition of processed Ar molecules represented by APC. It is a receptor for HIV by binding through the D1 domain to the gp120 virus.
Expressed on thymocytes (80-90%), mature T-lymphocytes (65% T-helpers), monocytes , macrophages , Langerhans cells , dendritic cells , as well as microglia .
Content
Structure
Like many membrane receptors, CD4 belongs to the superfamily of immunoglobulins.
Contains 4 Ig-domains (D 1 - D 4 ), extending to the outer surface of the cell membrane:
- D 1 and D 3 are similar to variable domains (IgV),
- D 2 and D 4 are similar to constant domains (IgC).
CD4 uses the D 1 domain to interact with the β 2 domain of MHC class II. Thus, T cells expressing CD4 are specific for MHC class II antigens, not class I.
The short intracellular region of CD4 contains an amino acid sequence that allows it to interact with Lck .
See also
- Differentiation cluster
Notes
- ↑ PDB 1cdh ; Ryu SE, Truneh A., Sweet RW, Hendrickson WA Structures of an HIV and MHC binding fragment from human CD4 as refined in two crystal lattices (Eng.) // Structure: journal. - 1994 .-- January ( vol. 2 , no. 1 ). - P. 59-74 . - DOI : 10.1016 / s0969-2126 (00) 00008-3 . - PMID 8075984 .
- ↑ Isobe M. , Huebner K. , Maddon PJ , Littman DR , Axel R. , Croce CM The gene encoding the T-cell surface protein T4 is located on human chromosome 12. // Proceedings of the National Academy of Sciences of the United States of America. - 1986. - Vol. 83, no. 12 . - P. 4399-4402. - DOI : 10.1073 / pnas.83.12.4399 . - PMID 3086883 .
- ↑ Ansari-Lari MA , Muzny DM , Lu J. , Lu F. , Lilley CE , Spanos S. , Malley T. , Gibbs RA A gene-rich cluster between the CD4 and triosephosphate isomerase genes at human chromosome 12p13. (English) // Genome research. - 1996. - Vol. 6, no. 4 . - P. 314-326. - DOI : 10.1101 / gr . 6.4.314 . - PMID 8723724 .
Literature
- Khaitov R. M. Immunology: a textbook for medical students. - M.: GEOTAR-Media, 2006 .-- 320 p.