LY9

LY9 (also known as Lymphocyte antigen 9) is a protein that in humans is encoded by the LY9 gene. LY9 is a member of the SLAM family of immunomodulatory receptors, and functions in T cell activation. It plays an essential role in regulation of immune responses.

Structure

The LY9 protein is a type I transmembrane protein that belongs to the signaling lymphocytic activation molecule (SLAM) family. It is characterized by the presence of an immunoglobulin (Ig) variable domain, a C2-type Ig domain, a transmembrane region, and a cytoplasmic tail containing four immunoreceptor tyrosine-based switch motifs (ITSMs).

Function

LY9 is expressed on the surface of T cells, B cells, and natural killer (NK) cells. It functions as a self-ligand, binding to other LY9 molecules on the surface of adjacent cells. This interaction leads to the recruitment and activation of Src family kinases, which then phosphorylate the ITSMs in the cytoplasmic tail of LY9. This phosphorylation serves as a docking site for SH2 domain-containing proteins, leading to the activation of downstream signaling pathways that regulate T cell activation, proliferation, and cytokine production.

Clinical significance

Alterations in the expression or function of LY9 have been associated with various autoimmune diseases, including systemic lupus erythematosus (SLE) and rheumatoid arthritis. In addition, LY9 has been implicated in the regulation of tumor immunity, with decreased expression of LY9 associated with poor prognosis in certain types of cancer.

See also

• SLAM family
• T cell
• B cell
• Natural killer cell
• Autoimmune disease
• Systemic lupus erythematosus
• Rheumatoid arthritis