2-CHLOROADENOSINE STIMULATES GRANULE EXOCYTOSIS FROM MOUSE NATURAL-KILLER-CELLS - EVIDENCE FOR SIGNAL-TRANSDUCTION THROUGH A NOVEL EXTRACELLULAR RECEPTOR

The effect of 2-chloroadenosine (2CA), an adenosine receptor agonist, on the activation status of mouse natural killer (NK) cells was determ ined. Splenic lymphocytes incubated with 2CA exocytosed an NH cell-ass ociated granzyme with N alpha-CBZ-L-lysine thiobenzyl ester (BLT) este rase activity in a dose- and time-dependent manner. Selective depletio n of NH cells by anti-asialoGM1 antibody plus complement pretreatment confirmed that NK cells were the source of the BLT esterase activity. 2CA-induced granule exocytosis was not reduced in the presence of the nucleoside uptake blockers NBTI, dilazep, or dipyridamole, indicating the involvement of an extracellular receptor. However, adenosine or ot her A(1),A(2), or A(3) cell-surface adenosine receptor agonists failed to trigger the exocytotic process. Furthermore, the nonselective aden osine receptor antagonist theophylline, as web as the selective A(1) r eceptor antagonist DPCPX and the selective A(2) receptor antagonist DM PX, did not interfere with 2CA-induced BLT esterase secretion. These d ata suggest that 2CA acts on NK cells via a novel (non-A(1)/A(2)/A(3)) cell-surface receptor. Grenistein, a protein tyrosine kinase inhibito r, and calphostin C, a protein kinase C inhibitor, both interfered wit h SCA-induced granule exocytosis. Pertussis toxin, an ADP-ribosylating toxin to which certain GTP-binding proteins are sensitive, also inhib ited 2CA-stimulated BLT esterase release. In addition, 2CA-induced gra nule exocytosis was reduced in the presence of cyclosporin A, an inhib itor of Ca2+-dependent signaling pathways, and the Ca2+-chelating agen t EGTA. We conclude that 2CA, acting through a novel extracellular rec eptor on mouse NK cells, triggers granule exocytosis via a Ca2+-depend ent signal transduction pathway that is coupled to GTP-binding protein s and involves protein tyrosine kinase and protein kinase C activation . (C) 1997 Academic Press.