Ly6

Ly6 also known as lymphocyte antigen 6 or urokinase-type plasminogen activator receptor (uPAR) is family of proteins that share a common structure but differ in their tissue expression patterns and function. Ly6 are cysteine-rich proteins that form disulfide bridges and contain a LU domain. These proteins are GPI-anchored to the cell membrane or are secreted. A total of 35 human and 61 mouse Ly6 family members have been identified.^[1] Depending on which tissues they are expressed 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.^[1][2] For example, they are involved in cell proliferation, cell migration, cell–cell interactions, immune cell maturation, macrophage activation, and cytokine production.^[3][1] Their overexpression or dysregulation, for example due to point mutations, is associated with tumorogenesis and autoimmune diseases.^[4][5] This family was discovered in the 1970s,^[6] and these proteins are still used as markers of distinct stage of leukocyte differentiation.^[3]