Functional Coupling of NKR-P1 Receptors to Various Heterotrimeric G Proteins in Rat Interleukin-2-activated Natural Killer Cells

NKR-P1 molecules constitute a family of type II membrane receptors in natural killer (NK) cells that preferentially activate NK cell killing and release of interferon-γ from these cells. Here, we demonstrate that anti-NKR-P1 enhances GTP binding in rat interleukin-2-activated NK cell membranes; GTP binding to Gi3α, Gsα, Gq,11α, and Gzα increased noticeably in these cell membranes after treatment with anti-NKR-P1. Western blot analysis of membrane proteins prepared from interleukin-2-activated NK cells reveals the presence of Gi1,2α, Gi3α, Goα, Gsα, Gq,11α, Gzα, and G12α, but not G13α. However, only αi3, αs, αq,11, and αz, but not αi1,2, αo, α12, or α13 subunits when immunoprecipitated with the appropriate anti-G protein antibodies, are associated with NKR-P1 when immunoblotted with anti-NKR-P1. Reciprocally, NKR-P1 immunoprecipitated with anti-NKR-P1 is associated with αi3, αs, αq,11, and αz immunoblotted with anti-G proteins. These results are the first to demonstrate the physical and functional coupling of NKR-P1 to the heterotrimeric G proteins in NK cells.