UL16-binding protein 1 (ULBP1) (ULBP1)

UL16-binding protein 1 (ULBP1) is a cell surface glycoprotein encoded by the *ULBP1* gene on chromosome 6. Unlike conventional MHC class I molecules, ULBP1 is structurally distinct, containing only the α1α2 domain linked to the cell membrane via a GPI anchor rather than a transmembrane segment. ULBP1 functions as a stress-induced ligand for the NKG2D receptor, an activating immune receptor expressed on natural killer cells and CD8+ T cells. When ULBP1 binds to NKG2D, it triggers multiple signal transduction pathways including JAK2, STAT5, ERK, and PI3K/Akt, leading to NK cell cytotoxicity and enhanced T cell responses. ULBP1 expression is upregulated in response to cellular stress conditions such as viral infection (particularly HCMV infection), malignant transformation, and other forms of cellular damage. The protein localizes to lipid rafts at the cell surface where it accumulates at NK cell immune synapses. Notably, some viruses like HCMV have evolved immune evasion strategies targeting ULBP1, with the viral UL16 protein binding to ULBP1 to prevent its surface localization.

Other names

UL16 binding protein 1NKG2D ligand ULBP-1

Not applicable as ULBP1 is a ligand, not a drug target. However, ULBP1 activates NKG2D signaling through binding to the NKG2D receptor on NK and T cells, triggering downstream signaling cascades.