The tyrosine kinase PYK-2/RAFTK regulates natural killer (NK) cell cytotoxic response, and is translocated and activated upon specific target cell recognition and killing

The compartmentalization of plasma membrane proteins has a key role in regu lation of lymphocyte activation and development of immunity. We found that the proline-rich tyrosine kinase-2 (PYK-2/RAFTK) colocalized with the micro tubule-organizing center (MTOC) at the trailing edge of migrating natural k iller (NK) cells. When polyclonal NK cells bound to K562 targets, PYK-2 tra nslocated to the area of NK-target cell interaction. The specificity of thi s process was assessed with NK cell clones bearing activatory or inhibitory forms of CD94/NKG2, The translocation of PYK-2. MTOC, and paxillin to the area of NK-target cell contact was regulated upon specific recognition of t arget cells through NK cell receptors, controlling target cell killing. Fur thermore, parallel in vitro kinase assays showed that PYK-2 was activated i n response to signals that specifically triggered its translocation and NK cell mediated cytotoxicity. The overexpression of both the wt and a dominan t-negative mutant of PYK-2, but not ZAP-70 wt, prevented the specific trans location of the MTOC and paxillin, and blocked the cytotoxic response of NK cells. Our data indicate that subcellular compartmentalization of PYK-2 co rrelates with effective signal transduction. Furthermore, they also suggest an important role for PYK-2 on the assembly of the signaling complexes tha t regulate the cytotoxic response.