Co-clustering of CD16 and NKG2D receptors augments degranulation of NK cells 2259276

Introduction It has been shown that CD16 and NKG2D receptors act synergistically to activate resting NK cells’ cytotoxicity and cytokine secretion. The molecular mechanism underlying the communication between the two receptors remains to be elucidated. Methods To study cooperativity between CD16 and NKG2D receptors, we exposed human primary polyclonal NK cells with CD16 176V/V-genotype to planar lipid bilayers presenting ICAM-1 adhesion molecules with activating Herceptin and/or NKG2D ligands. The interface formation, receptor clustering, recruitment of signaling molecules, MTOC polarization, and release of cytolytic granules were analyzed using confocal, TIRF, and super-resolution imaging. Results Exposure of NK cells to the bilayer containing only one ligand induced the emergence of Herceptin- or anti-NKG2D microclusters. Simultaneous engagement of the two receptors resulted in merging of Herceptin and anti-NKG2D clusters into mixed co-clusters. These mixed co-clusters have been found to accumulate PLC gamma-2 but not PLC-gamma-1 isoform. Our results demonstrated that co-clustering of the receptors resulted in a decrease of the motility of NK cells that was accompanied by the formation of a classical immunological synapse and a sustained Ca2+ influx, which led to augmented degranulation. Conclusion These data led us to propose a molecular mechanism that regulates the synergy between CD16 and NKG2D receptors. Funding Source UO1AI148117 NIH grant to Yuri Sykulev and Kerry S Campbell Topic Categories Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)