Association of TREM2-DAP12 with DAP10 is required for the regulation of PI3K in macrophages (98.18)

Abstract

Abstract The regulation of PI3K following TREM2 ligation in macrophages is unclear and was the focus of this study. Immunoprecipitation studies show that DAP10 signaling adapter protein is required for recruitment of PI3K (p85 subunit) to a TREM2-DAP12 complex following TREM2 ligation. Once recruited to the complex, PI3K mediates TREM2-DAP12 dependent activation of AKT and ERK1/2. Compared to wild type macrophages, TREM2 stimulation failed to induce p85 recruitment to DAP12 in DAP10-deficient macrophages leading to a significant reduction in activated AKT and ERK1/2. Calcium flux induced by TREM2 ligation remained intact in DAP10-deficient macrophages, indicating that it is DAP10-independent. Both DAP10 and DAP12 could associate with TREM2 and each other in macrophages suggesting a tri-molecular complex of TREM2-DAP12-DAP10. We further show that the recruitment of PI3K to TREM2-DAP12 complexes is negatively regulated by the lipid phosphatase, SHIP1, in a DAP12 ITAM- dependent manner. Confocal study showed that DAP10 is not required for the translocation of SHIP1 or DAP12 to the membrane. Thus, our data suggests that DAP10 is required for the recruitment and activation of PI3K induced by TREM2-DAP12 signaling but not for calcium flux. Experiments are now being done to further understand the role of this tri- molecular complex (TREM2-DAP12-DAP10) leading to optimal functioning of bone marrow- derived macrophages.