HEM1 deficiency disrupts mTORC2 and F-actin control in inherited immunodysregulatory disease
Sarah A. Cook, William A. Comrie, M. Cecilia Poli, Morgan Similuk, Andrew J. Oler, Aiman Faruqi, Douglas B. Kuhns, Sheng Yang, Alexander Vargas‐Hernández, Alexandre F. Carisey, Benjamin Fournier, David E. Anderson, Susan Price, Margery Smelkinson, Wadih Abou Chahla, Lisa R. Forbes, Emily M. Mace, Tram N. Cao, Zeynep Coban‐Akdemir, Shalini N. Jhangiani, Donna M. Muzny, Richard A. Gibbs, James R. Lupski, Jordan S. Orange, Geoff D.E. Cuvelier, Moza Al Hassani, Nawal Al Kaabi, Zain Al Yafei, Soma Jyonouchi, Nikita Raje, Jason W. Caldwell, Yanping Huang, Janis K. Burkhardt, Sylvain Latour, Baoyu Chen, Gehad ElGhazali, V. Koneti Rao, Iván K. Chinn, Michael J. Lenardo
Abstract
, which encodes the hematopoietic-specific HEM1 protein. These mutations cause the loss of the HEM1 protein and the WAVE regulatory complex (WRC) or disrupt binding to the WRC regulator, Arf1, thereby impairing actin polymerization, synapse formation, and immune cell migration. Diminished cortical actin networks caused by WRC loss led to uncontrolled cytokine release and immune hyperresponsiveness. HEM1 loss also blocked mechanistic target of rapamycin complex 2 (mTORC2)-dependent AKT phosphorylation, T cell proliferation, and selected effector functions, leading to immunodeficiency. Thus, the evolutionarily conserved HEM1 protein simultaneously regulates filamentous actin (F-actin) and mTORC2 signaling to achieve equipoise in immune responses.