1q69

Structural highlights

Disease

[CD8A_HUMAN] Defects in CD8A are a cause of familial CD8 deficiency (CD8 deficiency) [MIM:608957]. Familial CD8 deficiency is a novel autosomal recessive immunologic defect characterized by absence of CD8+ cells, leading to recurrent bacterial infections. [LCK_HUMAN] Severe combined immunodeficiency due to LCK deficiency. Note=A chromosomal aberration involving LCK is found in leukemias. Translocation t(1;7)(p34;q34) with TCRB.

Function

[CD8A_HUMAN] Identifies cytotoxic/suppressor T-cells that interact with MHC class I bearing targets. CD8 is thought to play a role in the process of T-cell mediated killing. CD8 alpha chains binds to class I MHC molecules alpha-3 domains. [LCK_HUMAN] Non-receptor tyrosine-protein kinase that plays an essential role in the selection and maturation of developing T-cells in the thymus and in the function of mature T-cells. Plays a key role in T-cell antigen receptor (TCR)-linked signal transduction pathways. Constitutively associated with the cytoplasmic portions of the CD4 and CD8 surface receptors. Association of the TCR with a peptide antigen-bound MHC complex facilitates the interaction of CD4 and CD8 with MHC class II and class I molecules, respectively, thereby recruiting the associated LCK protein to the vicinity of the TCR/CD3 complex. LCK then phosphorylates tyrosines residues within the immunoreceptor tyrosine-based activation motifs (ITAM) of the cytoplasmic tails of the TCR-gamma chains and CD3 subunits, initiating the TCR/CD3 signaling pathway. Once stimulated, the TCR recruits the tyrosine kinase ZAP70, that becomes phosphorylated and activated by LCK. Following this, a large number of signaling molecules are recruited, ultimately leading to lymphokine production. LCK also contributes to signaling by other receptor molecules. Associates directly with the cytoplasmic tail of CD2, which leads to hyperphosphorylation and activation of LCK. Also plays a role in the IL2 receptor-linked signaling pathway that controls the T-cell proliferative response. Binding of IL2 to its receptor results in increased activity of LCK. Is expressed at all stages of thymocyte development and is required for the regulation of maturation events that are governed by both pre-TCR and mature alpha beta TCR. Phosphorylates other substrates including RUNX3, PTK2B/PYK2, the microtubule-associated protein MAPT, RHOH or TYROBP.^{[1] [2] [3] [4] [5] [6]}

See Also

• CD8 3D structures
• Tyrosine kinase 3D structures

References

1. ↑ Gelkop S, Gish GD, Babichev Y, Pawson T, Isakov N. T cell activation-induced CrkII binding to the Zap70 protein tyrosine kinase is mediated by Lck-dependent phosphorylation of Zap70 tyrosine 315. J Immunol. 2005 Dec 15;175(12):8123-32. PMID:16339550
2. ↑ Mason LH, Willette-Brown J, Taylor LS, McVicar DW. Regulation of Ly49D/DAP12 signal transduction by Src-family kinases and CD45. J Immunol. 2006 Jun 1;176(11):6615-23. PMID:16709819
3. ↑ Goh YM, Cinghu S, Hong ET, Lee YS, Kim JH, Jang JW, Li YH, Chi XZ, Lee KS, Wee H, Ito Y, Oh BC, Bae SC. Src kinase phosphorylates RUNX3 at tyrosine residues and localizes the protein in the cytoplasm. J Biol Chem. 2010 Mar 26;285(13):10122-9. doi: 10.1074/jbc.M109.071381. Epub 2010, Jan 25. PMID:20100835 doi:10.1074/jbc.M109.071381
4. ↑ Collins M, Tremblay M, Chapman N, Curtiss M, Rothman PB, Houtman JC. The T cell receptor-mediated phosphorylation of Pyk2 tyrosines 402 and 580 occurs via a distinct mechanism than other receptor systems. J Leukoc Biol. 2009 Dec 22. PMID:20028775 doi:jlb.0409227
5. ↑ Wang H, Zeng X, Fan Z, Lim B. RhoH modulates pre-TCR and TCR signalling by regulating LCK. Cell Signal. 2011 Jan;23(1):249-58. doi: 10.1016/j.cellsig.2010.09.009. Epub 2010, Sep 16. PMID:20851766 doi:10.1016/j.cellsig.2010.09.009
6. ↑ Scales TM, Derkinderen P, Leung KY, Byers HL, Ward MA, Price C, Bird IN, Perera T, Kellie S, Williamson R, Anderton BH, Reynolds CH. Tyrosine phosphorylation of tau by the SRC family kinases lck and fyn. Mol Neurodegener. 2011 Jan 26;6:12. doi: 10.1186/1750-1326-6-12. PMID:21269457 doi:10.1186/1750-1326-6-12
7. ↑ Kim PW, Sun ZY, Blacklow SC, Wagner G, Eck MJ. A zinc clasp structure tethers Lck to T cell coreceptors CD4 and CD8. Science. 2003 Sep 19;301(5640):1725-8. PMID:14500983 doi:10.1126/science.1085643