Lytic granule convergence depends on Src kinase but occurs independently of PI3K, MEK, and PLCγ activity. Time-lapse frames of lytic granule movement in YTS GFP-tubulin cells pretreated with (A) LY294002, (B) PD98059, or (C) U73122 on an anti-CD28– or an anti-CD11a–coated surface. In each image, confocal immunofluorescence in the plane of the MTOC is shown. Green, GFP-tubulin; red, LysoTracker-loaded acidified organelles. Zero minutes represents the time at which the NK cell appeared to contact the glass surface. (D) Cytotoxicity assay (4-hour ⁵¹Cr release) of YTS cells against 721.221 target cells showing loss of function after treatment with various inhibitors. AZM 475271 provided 75% inhibition at a 10:1 E:T ratio. (E-F) Quantitative analyses of lytic granule distance from the MTOC as a function of time (initial vs final) as measured by mean MTOC to granule distance in 9 to 10 cells per condition in DMSO-treated or inhibitor-treated YTS GFP-tubulin cells on (E) anti-CD28– or (F) anti-CD11a–coated surfaces. Error bars show ±SD. Excepting PP2, mean distance of lytic granules from the MTOC was not significantly different in any inhibitor-treated NK cells compared with DMSO-treated NK cells; distance of lytic granules from the MTOC was significantly greater at time point zero than at the end of the assay (*P < .05).