T cell receptor
Name = T cell receptor alpha locus
HGNCid = 12027
Symbol = TRA@
AltSymbols = TCRA
EntrezGene = 6955
OMIM = 186880
Chromosome = 14
Arm = q
Band = 11.2
LocusSupplementaryData = proteinShort
Name = T cell receptor beta locus
HGNCid = 12155
Symbol = TRB@
AltSymbols = TCRB
EntrezGene = 6957
OMIM = 186930
Chromosome = 7
Arm = q
Band = 34
LocusSupplementaryData = The T cell receptor or TCR is a molecule found on the surface of
T lymphocytes(or T cells) that is, in general, responsible for recognizing antigens bound to major histocompatibility complex(MHC) molecules.
It is a
heterodimerconsisting of an alpha and beta chain in 95% of T cells, whereas 5% of T cells have TCRs consisting of gamma and delta chains.
Engagement of the TCR with antigen and MHC results in activation of its T lymphocyte through a series of biochemical events mediated by associated enzymes, co-receptors, and specialized accessory molecules.
tructural characteristics of the TCR
Each chain of the TCR is a member of the
immunoglobulin superfamilyand possesses one N-terminal immunoglobulin (Ig)-variable (V) domain, one Ig-constant (C) domain, a transmembrane/cell membrane-spanning region, and a short cytoplasmic tail at the C-terminal end.
The variable domain of both the TCR α-chain and β-chain have three hypervariable or
complementarity determining regions (CDRs), whereas the variable region of the β-chain has an additional area of hypervariability (HV4) that does not normally contact antigen and therefore is not considered a CDR.
CDR3 is the main CDR responsible for recognizing processed antigen, although CDR1 of the alpha chain has also been shown to interact with the
N-terminalpart of the antigenic peptide, whereas CDR1 of the beta chain interacts with the C-terminalpart of the peptide.
CDR2 is thought to recognize the MHC. CDR4 of the β-chain is not thought to participate in antigen recognition, but has been shown to interact with
The constant domain of the TCR domain consists of short connecting sequences in which a cysteine residue forms disulfide bonds, which forms a link between the two chains.
Generation of the TCR
Processes for TCR formation are similar to those described for
B-cellantigen receptors, otherwise known as immunoglobulins.
* The TCR "alpha chain" is generated by VJ recombination, whereas the "beta chain" is generated by
V(D)J recombination(both involve a somewhat random joining of gene segments to generate the complete TCR chain).
* In a similar manner, generation of the TCR "gamma chain" involves VJ recombination, whereas generation of the TCR "delta chain" occurs by V(D)J recombination.
The intersection of these specific regions (V and J for the alpha or gamma chain, V D and J for the beta or delta chain) corresponds to the CDR3 region that is important for antigen-MHC recognition (see above).
Furthermore, it is the unique combination of the segments at this region, along with
palindromicand random N- and P- nucleotide additions, which accounts for the great diversity in specificity of the T cell receptor for processed antigen.
The TCR Complex
The transmembrane region of the TCR is composed of positively-charged
It is thought that this allows the TCR to associate with other molecules like CD3, that possess three distinct chains (γ, δ, and ε) in mammals and the
These accessory molecules have negatively-charged
transmembraneregions and are vital to propagating the signal from the TCR into the cell; the cytoplasmictail of the TCR is extremely short, making it unlikely to participate in signaling.
The CD3- and ζ-chains, together with the TCR, form what is known as the "T cell receptor complex."
The signal from the T cell complex is enhanced by simultaneous binding of the MHC molecules by a specific
helper T cells, this co-receptor is CD4that exclusively binds the class II MHC.
cytotoxic T cells, this co-receptor is CD8that is specific for class I MHC.
The co-receptor not only ensures the specificity of the TCR for the correctly-presented antigen but also allows prolonged engagement between the
antigen presenting celland the T cell and recruits essential molecules (e.g., LCK) inside the cell that are involved in the signaling of that activated T lymphocyte.
* - Zeta-zeta dimer of T cell receptor
Wikimedia Foundation. 2010.
Look at other dictionaries:
B-cell receptor — B cell receptors are proteins found on the surface of B cells.cite journal |author=Barral P, Eckl Dorna J, Harwood NE, et al |title=B cell receptor mediated uptake of CD1d restricted antigen augments antibody responses by recruiting invariant NKT … Wikipedia
T-cell receptor — Récepteur des cellules T Pour les articles homonymes, voir TCR. Le récepteur des cellules T ou TCR (de l’anglais T Cell receptor) est un complexe moléculaire qui se trouve sur la membrane des lymphocytes T (ou cellules T). Ce récepteur… … Wikipédia en Français
T-cell receptor — The antigen recognising receptor on the surface of T cells. Heterodimeric (disulphide linked), one of the immunoglobulin superfamily of proteins; binds antigen in association with the major histocompatibility complex (MHC), leading to the… … Dictionary of molecular biology
T cell receptor — An antigen binding protein, located on the surface of mammalian killer T cells, which mediates the cellular immune response. T cell antigen encoding genes are assembled from gene segments by somatic recombination processes that occur during… … Glossary of Biotechnology
T-cell receptor — A device used by T cells for recognizing specific antigens. T cells have receptors that are activated exclusively by a target antigen … Medical dictionary
Artificial T cell receptor — Artificial T cell receptors (also known as chimeric T cell receptors) are engineered molecules, which when expressed by T cells, redirect the T cells to kill a target cell with a specificity dictated by the artificial receptor. [cite journal| url … Wikipedia
Receptor editing — is a process that occurs during the maturation of B cells, which are part of the adaptive immune system. This process has the aim to change the specificity of the antigen receptor of immature B cells, in order to rescue them from programmed cell… … Wikipedia
Receptor de linfocitos T — alfa HUGO 12027 Símbolo TRA@ Símbolos alt. TCRA … Wikipedia Español
Cell surface receptor — The seven transmembrane α helix structure of a G protein coupled receptor Cell surface receptors (membrane receptors, transmembrane receptors) are specialized integral membrane proteins that take part in communication between the cell and the… … Wikipedia
Cell signaling — is part of a complex system of communication that governs basic cellular activities and coordinates cell actions. [Witzany, G. (2000). Life: The Communicative Structure. Norderstedt, Libri BoD.] The ability of cells to perceive and correctly… … Wikipedia