This information is current as To Regulate NK Cell Cytotoxicity ProteinTalin and Wiskott-Aldrich Syndrome Dedicator of Cytokinesis 8 Interacts with Lou and

Recently, patients with mutations in DOCK8 have been reported to have a combined immunodeficiency characterized by cuta-neous viral infections and allergies. NK cells represent a first-line defense against viral infections, suggesting that DOCK8 might participate in NK cell function. In this study, we demonstrate that DOCK8-suppressed human NK cells showed defects in natural cytotoxicity as well as specific activating receptor-mediated NK cytotoxicity. Additionally, compared with control NK cells, NK cells depleted of DOCK8 showed defective conjugate formation, along with decreased polarization of LFA-1, F-actin, and cytolytic granules toward the cytotoxic synapse. Using a proteomic approach, we found that DOCK8 exists in a macromolecular complex with the Wiskott-Aldrich syndrome protein, an actin nucleation-promoting factor activated by CDC42, as well as talin, which is required for integrin-mediated adhesion. Taken together, our results demonstrate an important role for DOCK8 in NK cell effector function and provide important new mechanistic insight into how DOCK8 regulates F-actin and integrin-mediated adhesion in immune cells. T he dedicator of cytokinesis (DOCK) 180 family of guanine nucleotide exchange factors (GEF), of which there are 11 known genes, participates in the activation of Rho family proteins and contributes to multiple cellular processes, including cell migration, phagocytosis, and immune homeostasis (1–3). In 2009, mutations in the DOCK8 gene were found to be associated with cases of autosomal recessive hyper-IgE syndrome (4, 5). The disease showed an autosomal recessive pattern of inheritance, and all reported patients harbored homozygous or compound hetero-zygous mutations on both alleles, leading to either null or non-functional expression of DOCK8. The main clinical symptoms of the patients were recurrent sinopulmonary and cutaneous infections and severe allergies. Immunologically, patients showed high IgE and eosinophil numbers in their sera, defects in generation of long-lasting humoral immunity, and T cells with limited cellular proliferation following activation (4–7). Direct killing by CTL or NK cells against target cells is required for clearance of intracellular pathogens, including virus-infected or transformed cells (8–10). The observation that most DOCK8-deficient patients are susceptible to recurrent viral infections suggests the existence of a general deficiency of cytotoxic lymphocytes. Supporting this hypothesis, one group reported T cell lymphopenia and impaired T cell expansion in DOCK8-deficient patients (5). However, another clinical report found that T cell numbers in patients were within normal range (4), and a recent study reported that mouse CTLs harboring a mutation within the DOCK8 DOCK homology region 2 (DHR2) domain had no killing defect …