NKR-P1, an activating molecule on rat natural killer cells, stimulates phosphoinositide turnover and a rise in intracellular calcium.
NKR-P1 is a 60-kDa homodimer expressed on all rat NK cells. Previous studies by others suggest that NKR-P1 may play a role in NK cell activation because antibody to NKR-P1 stimulates the release of granules from NK cells, and anti-NKR-P1 causes redirected lysis by activated NK cells against targets that express FcR. To examine the mechanism of transmembrane signaling by NKR-P1, we studied the rat NK cell line, RNK-16. We here demonstrate that F(ab')2 antibody to NKR-P1 stimulates phosphoinositide turnover and a rise in intracellular calcium within RNK-16 cells. The response is augmented by cross-linking the F(ab')2 antibody. The phosphoinositide/calcium pathway is also stimulated by NKR-P1 in activated rat NK cells, although no response is detectable in polymorphonuclear cells, which also express NKR-P1. We also demonstrate that RNK-16 cells kill the anti-NKR-P1 (3.2.3) hybridoma and that exposure to the hybridoma target cells stimulates phosphoinositide turnover in RNK-16 cells. Both killing and phosphoinositide turnover are inhibited by F(ab')2 anti-NKR-P1, implicating NKR-P1 in both responses. In contrast, neither cytotoxicity nor phosphoinositide turnover is appreciably blocked by F(ab')2 anti-NKR-P1 in response to YAC-1 targets. Thus, with either target, killing is linked to phosphoinositide turnover, but killing of YAC-1 involves pathways that differ from those that direct killing of the anti-NKR-P1 hybridoma. Our studies support the hypothesis that NKR-P1 may serve as an activating cell-surface receptor on NK cells, and they clarify the mechanisms by which it activates NK cells.
Department of Medicine, San Francisco Veterans Administration Medical Center, CA 94121.
J C
JC
Ryan
E C
EC
Niemi
R D
RD
Goldfien
J C
JC
Hiserodt
W E
WE
Seaman
D000818:Animals; D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D003602:Cytotoxicity, Immunologic; D007111:Immunity, Cellular; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism; D007694:Killer Cells, Natural / Q000276:immunology*; D037181:Lectins, C-Type; D055651:NK Cell Lectin-Like Receptor Subfamily B; D009504:Neutrophils / Q000502:physiology; D051381:Rats; D011971:Receptors, Immunologic / Q000502:physiology*; D015398:Signal Transduction
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D007295:Inositol Phosphates; D037181:Lectins, C-Type; D055651:NK Cell Lectin-Like Receptor Subfamily B; D011971:Receptors, Immunologic; D002118:Calcium