LIGHT, also known as tumor necrosis factor superfamily member 14 (TNFSF14), is a secreted protein of the TNF superfamily.[5][6][7] It is recognized by herpesvirus entry mediator (HVEM), as well as decoy receptor 3.
LIGHT stands for "homologous to lymphotoxin, exhibits inducible expression and competes with HSV glycoprotein D for binding to herpesvirus entry mediator, a receptor expressed on T lymphocytes". In the cluster of differentiation terminology it is classified as CD258.
The protein encoded by this gene is a member of the tumor necrosis factor (TNF) ligand family. This protein is a ligand for TNFRSF14, which is a member of the tumor necrosis factor receptor superfamily, and which is also known as a herpesvirus entry mediator (HVEM). Two alternatively spliced transcript variant encoding distinct isoforms have been reported.[6]
This protein may function as a costimulatory factor for the activation of lymphoid cells and as a deterrent to infection by herpesvirus. This protein has been shown to stimulate the proliferation of T cells,[8] trigger apoptosis of various tumor cells[9] and play a role in vascular normalisation processes.[10] This protein is also reported to prevent tumor necrosis factor alpha-mediated apoptosis in primary hepatocytes.[11]
LIGHT has been shown to interact with TNFRSF14,[12][13] TNFRSF6B,[12][13][14] BIRC2,[15] TRAF2[15] and TRAF3.[15]
Similar to how CD4 is the primary mediating receptor in HIV infection, the HSV glycoprotein (gD) binds to the HVEM receptor which is demanded by TNFSF14/LIGHT lowering the ability for LIGHT to activate the NFκB pathway. NFκB is a survival factor helping to inhibit apoptosis which triggers a pathway inhibiting caspase 8. When gD from HSV binds to HVEM, LIGHT is non-competitively inhibited from binding, encouraging apoptosis in the infected cell.[7]