TRAF6 Mediates Basal Activation of NF-κB Necessary for Hematopoietic Stem Cell Homeostasis
2018
Jing Fang | Tomoya Muto | Maria Kleppe | Lyndsey C. Bolanos | Kathleen M. Hueneman | Callum S. Walker | Leesa Sampson | Ashley M. Wellendorf | Kashish Chetal | Kwangmin Choi | Nathan Salomonis | Yongwon Choi | Yi Zheng | Jose A. Cancelas | Ross L. Levine | Daniel T. Starczynowski
Summary: Basal nuclear factor κB (NF-κB) activation is required for hematopoietic stem cell (HSC) homeostasis in the absence of inflammation; however, the upstream mediators of basal NF-κB signaling are less well understood. Here, we describe TRAF6 as an essential regulator of HSC homeostasis through basal activation of NF-κB. Hematopoietic-specific deletion of Traf6 resulted in impaired HSC self-renewal and fitness. Gene expression, RNA splicing, and molecular analyses of Traf6-deficient hematopoietic stem/progenitor cells (HSPCs) revealed changes in adaptive immune signaling, innate immune signaling, and NF-κB signaling, indicating that signaling via TRAF6 in the absence of cytokine stimulation and/or infection is required for HSC function. In addition, we established that loss of IκB kinase beta (IKKβ)-mediated NF-κB activation is responsible for the major hematopoietic defects observed in Traf6-deficient HSPC as deletion of IKKβ similarly resulted in impaired HSC self-renewal and fitness. Taken together, TRAF6 is required for HSC homeostasis by maintaining a minimal threshold level of IKKβ/NF-κB signaling. : Fang et al. identify TRAF6 as an essential regulator of hematopoietic stem cell (HSC) self-renewal and quiescence. TRAF6 preserves HSC homeostasis by maintaining a minimal threshold level of NF-κB signaling in the absence of inflammation. Keywords: TRAF6, hematopoietic stem cell, NF-kB, innate immune signaling, toll-like receptor, IKKbeta
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