PI3K links NKG2D signaling to a CrkL pathway involved in natural killer cell adhesion, polarity, and granule secretion.
The NK cell-activating receptor NKG2D plays a critical role in the destruction of malignant cells, but many of the cell-signaling mechanisms governing NKG2D-mediated cellular cytotoxicity are unknown. We have identified an NKG2D-mediated signaling pathway that governs both conjugate formation and cytotoxic granule polarization. We demonstrate that an interaction between the regulatory subunit of PI3K, p85, and the adaptor protein CrkL is required for efficient NKG2D-mediated cellular cytotoxicity. We show decreased NK cell-target cell conjugate formation in NK cells treated with PI3K inhibitors or depleted of CrkL. Independent of adhesion, we find that microtubule organization center polarization toward target cells expressing the NKG2D ligand MICA or toward anti-NKG2D-coated beads is impaired in the absence of CrkL. Ab-stimulated granule release is also impaired in NK cells depleted of CrkL. Furthermore, our data indicate that the small Ras family GTPase Rap1 is activated downstream of NKG2D engagement in a PI3K- and CrkL-dependent manner and is required for conjugate formation, MTOC (microtubule organizing center) polarization, and NKG2D-dependent cellular cytotoxicity. Taken together, our data identify an NKG2D-activated signaling pathway that collectively orchestrates NK cell adhesion, cell polarization, and granule release.
Segovis
Colin M
CM
Department of Immunology, .College of Medicine,Mayo Clinic, Rochester, MN 55905, USA
Schoon
Renee A
RA
Dick
Christopher J
CJ
Nacusi
Lucas P
LP
Leibson
Paul J
PJ
Billadeau
Daniel D
DD
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D002448:Cell Adhesion; D002460:Cell Line; D016764:Cell Polarity; D006801:Humans; D007694:Killer Cells, Natural / Q000166:cytology* / Q000276:immunology; D022101:Microtubule-Organizing Center; D055655:NK Cell Lectin-Like Receptor Subfamily K / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000276:immunology*; D022142:Secretory Vesicles; D015398:Signal Transduction / Q000276:immunology*; D020827:rap1 GTP-Binding Proteins
D048868:Adaptor Proteins, Signal Transducing; C082869:CRKL protein; D055655:NK Cell Lectin-Like Receptor Subfamily K; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases; D020827:rap1 GTP-Binding Proteins