NKG2D ligand 1 (UL16-binding protein 1, NKG2DL1, N2DL-1, ALCAN-beta, retinoic acid early transcript 1I, ULBP1, N2DL1, RAET1I)
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Function
- ligand for NKG2D receptor, together with at least ULBP2 & ULBP3
- ULBPs activate multiple signaling pathways in primary NK cells, resulting in production of cytokines & chemokines
- binding of ULBPs ligands to NKG2D induces Ca+2 mobilization & activation of JAK2, STAT5, ERK & PI3K kinase/Akt signal transduction pathway
- does not bind to beta2-microglobulin
Structure
- belongs to the MHC class I family
- ULBPs are unusual members of the extended MHC class 1 superfamily, because they do not contain the alpha 3 domain & they lack a transmembrane domain
Compartment
cell membrane, GPI-anchor, secreted
Expression
- expressed in T-cells, B-cells, heart, brain, lung, liver, testis, lymph node, thymus, tonsil, bone marrow & in fetal heart, brain, lung & liver
Pathology
- in CMV infected cells, interacts with soluble CMV glycoprotein UL16.
- interaction with UL16 blocked the interaction with NKG2D receptor, providing a mechanism by which CMV infected cells might escape the immune system
- UL16 also causes ULBP2 to be retained in the ER & cis-Golgi so that it does not reach the cell surface
- expressed in erythroleukemia cell lines