Brief Definitive Report 817 Differential Requirements for Vav Proteins in DAP 10-and ITAM-mediated NK Cell Cytotoxicity

Natural killer (NK) cells express multiple activating receptors that initiate signaling cascades through DAP10or immunoreceptor tyrosine-based activation motif–containing adapters, including DAP12 and FcR . Among downstream signaling mediators, the guanine nucleotide exchange factor Vav1 carries out a key role in activation. However, whether Vav1 regulates only some or all NK cell–activating pathways is matter of debate. It is also possible that two other Vav family molecules, Vav2 and Vav3, are involved in NK cell activation. Here, we examine the relative contribution of each of these exchange factors to NK cell–mediated cytotoxicity using mice lacking one, two, or all three Vav proteins. We found that Vav1 deficiency is sufficient to disrupt DAP10-mediated cytotoxicity, whereas lack of Vav2 and Vav3 profoundly impairs FcR and DAP12-mediated cytotoxicity. Our results provide evidence that these three Vav proteins function specifically in distinct pathways that trigger NK cell cytotoxicity.