# Ly6 > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Ly6 > Markdown URL: https://mediated.wiki/source/Ly6.md > Source: https://en.wikipedia.org/wiki/Ly6 > Source revision: 1187434179 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) '''Ly6''' also known as '''lymphocyte antigen 6''' or '''urokinase-type plasminogen activator receptor''' (uPAR) is [family](/source/protein_family) of proteins that share a common structure but differ in their tissue [expression](/source/gene_expression) patterns and function. Ly6 are [cysteine-rich](/source/cysteine-rich_protein) proteins that form [disulfide bridges](/source/disulfide_bridges) and contain a [LU domain](/source/LU_domain). These proteins are [GPI-anchor](/source/GPI-anchor)ed to the [cell membrane](/source/cell_membrane) or are secreted. A total of 35 human and 61 mouse Ly6 family members have been identified. Depending on which tissues they are [expressed](/source/gene_expression) in, LY6 family members have different roles. They are expressed in various types of tissues and their expression dependent on the stage of [cell differentiation](/source/cellular_differentiation).{{cite journal | vauthors = Loughner CL, Bruford EA, McAndrews MS, Delp EE, Swamynathan S, Swamynathan SK | title = Organization, evolution and functions of the human and mouse Ly6/uPAR family genes | journal = Human Genomics | volume = 10 | issue = 1 | pages = 10 | date = April 2016 | pmid = 27098205 | pmc = 4839075 | doi = 10.1186/s40246-016-0074-2 | doi-access = free }}{{cite journal | vauthors = Lee PY, Wang JX, Parisini E, Dascher CC, Nigrovic PA | title = Ly6 family proteins in neutrophil biology | journal = Journal of Leukocyte Biology | volume = 94 | issue = 4 | pages = 585–94 | date = October 2013 | pmid = 23543767 | doi = 10.1189/jlb.0113014 | s2cid = 1252351 }} For example, they are involved in [cell proliferation](/source/cell_growth), [cell migration](/source/cell_migration), [cell–cell interaction](/source/cell%E2%80%93cell_interaction)s, immune cell maturation, [macrophage](/source/macrophage) activation, and [cytokine](/source/cytokine) production. Their overexpression or dysregulation, for example due to [point mutation](/source/point_mutation)s, is associated with [tumorogenesis](/source/carcinogenesis) and [autoimmune disease](/source/autoimmune_disease)s.{{cite journal | vauthors = Upadhyay G | title = Emerging Role of Lymphocyte Antigen-6 Family of Genes in Cancer and Immune Cells | journal = Frontiers in Immunology | volume = 10 | pages = 819 | date = 2019 | pmid = 31068932 | pmc = 6491625 | doi = 10.3389/fimmu.2019.00819 | doi-access = free }}{{cite journal | vauthors = Sidenius N, Blasi F | title = The urokinase plasminogen activator system in cancer: recent advances and implication for prognosis and therapy | journal = Cancer and Metastasis Reviews | volume = 22 | issue = 2–3 | pages = 205–22 | date = June 2003 | pmid = 12784997 | doi = 10.1023/A:1023099415940 | s2cid = 5765336 }} This family was discovered in the 1970s,{{cite journal | vauthors = McKenzie IF, Gardiner J, Cherry M, Snell GD | title = Lymphocyte antigens: Ly-4, Ly-6, and Ly-7 | journal = Transplantation Proceedings | volume = 9 | issue = 1 | pages = 667–9 | date = March 1977 | pmid = 68598 }} and these proteins are still used as markers of distinct stage of [leukocyte](/source/White_blood_cell) [differentiation](/source/Cellular_differentiation).{{cite journal | vauthors = Kong HK, Park JH | title = Characterization and function of human Ly-6/uPAR molecules | journal = BMB Reports | volume = 45 | issue = 11 | pages = 595–603 | date = November 2012 | pmid = 23186997 | pmc = 4133805 | doi = 10.5483/bmbrep.2012.45.11.210 }} == Gene organization == [Gene](/source/Gene)s encoding human Ly6 family members are located in clusters on [chromosome](/source/chromosome)s 6, 8, 11 and 19. In the murine [genome](/source/genome) family members are located on chromosomes 17, 15, 9 and 7, respectively. Genes encoding Ly6 proteins with one [LU domain](/source/LU_domain) consist of 3 [exon](/source/exon)s and 2 [intron](/source/intron)s. The first exon encodes the [signal peptide](/source/signal_peptide), Exons 2 and 3 encode the LU domain, and exon 3 also encodes the [GPI anchor](/source/GPI_anchor). == Protein structure == Ly6 proteins are characterized by the [LU domain](/source/LU_domain). Typically, they contain one [LU domain](/source/LU_domain), but some members of the family have multiple LU domains. The LU domain consists of 60-80 [AA](/source/Amino_acid) and contains 10 [cysteine](/source/cysteine)s arranged in a specific pattern that allows the creation of 5 [disulfide bridges](/source/disulfide_bridges) which in turn allow the formation of a [three-fingered](/source/Three-finger_superfamily) (3F) structural motif. Based on their [subcellular localization](/source/subcellular_localization), these proteins are classified as [GPI-anchor](/source/GPI-anchor)ed to the [cell membrane](/source/cell_membrane) or secreted. == Expression == Although the Ly6 family members share a common structure, their [expression](/source/Gene_expression) varies in different [tissues](/source/Tissue_(biology)) and is regulated depending on the stage of cell [differentiation](/source/Cellular_differentiation). Many Ly6 family members are expressed in [hematopoietic](/source/Haematopoietic_system) precursors and differentiated [hematopoietic cells](/source/Hematopoietic_stem_cell) in a lineage-specific manner and making them useful [cell surface markers](/source/cell_surface_markers) for [leukocytes](/source/White_blood_cell), facilitating identification of distinct [leukocyte](/source/White_blood_cell) sub-population. Further, the Ly6 family proteins are also expressed, for example, by [sperm](/source/sperm), [neuron](/source/neuron)s, [keratinocyte](/source/keratinocyte)s and [epithelial cell](/source/epithelial_cell)s. == Function == Ly6 family proteins have different functions depending on [expression](/source/Gene_expression) in different [tissue](/source/Tissue_(biology))s. They play an important role in the [immune](/source/Immune_system) response to [infection](/source/infection) and maintaining [homeostasis](/source/homeostasis) in response to varying environmental conditions. It is involved in [cell proliferation](/source/cell_growth), [cell migration](/source/cell_migration), [cell–cell interaction](/source/cell%E2%80%93cell_interaction)s, immune cell maturation, [macrophage](/source/macrophage) activation, and [cytokine](/source/cytokine) production. It is also involved in [complement](/source/Complement_system) activity, neuronal activity, [angiogenesis](/source/angiogenesis), [tumorogenesis](/source/carcinogenesis) and wound healing. == Clinical relevance == Many Ly6 family proteins (with the notable exception of [SLURP1](/source/SLURP1)) are over-expressed in [inflamed](/source/inflammation) tissues and in [tumor](/source/tumor)s. They are therefore used as [tumor marker](/source/tumor_marker)s and are also potential [therapeutic target](/source/Biological_target)s. Some point [mutation](/source/mutation)s in Ly6 family proteins are associated with [autoimmune disease](/source/autoimmune_disease)s, such as [psoriasis vulgaris](/source/psoriasis_vulgaris). ==Ly6 proteins== Examples of Ly6 proteins include: *[LY6E](/source/LY6E) *[LYNX1](/source/LYNX1) *[LYPD1](/source/LYPD1) *[LYPD3](/source/LYPD3) *[LYPD5](/source/Ly6%2Fplaur_domain_containing_5) *[LYPD8](/source/LYPD8) *[LYPD6B](/source/LYPD6B) ==References == {{reflist}} Category:Protein families --- Adapted from the Wikipedia article [Ly6](https://en.wikipedia.org/wiki/Ly6) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Ly6?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.