BST2 Facilitates Activation of Hematopoietic Stem Cells Through ERK Signaling

Abstract

The proinflammatory cytokine interferon-gamma (IFNγ) is upregulated in a variety of infections and contributes to bone marrow failure through hematopoietic stem cell (HSC) activation and subsequent exhaustion. The cell surface protein, bone marrow stromal antigen 2 (BST2), is a key mediator of this process, as it is induced upon interferon stimulation and required for interferon-dependent HSC activation. To identify the mechanism by which BST2 promotes interferon-dependent HSC activation, we evaluated its role in niche localization, immune cell function, lipid raft formation, and intracellular signaling. Our studies indicated that knock out (KO) of BST2 in a murine model does not disrupt immune cell responses to interferon-inducing mycobacterial infection. Furthermore, intravital imaging studies indicate that BST2 KO does not disrupt localization of HSCs relative to endothelial or osteoblastic niches in the bone marrow. However, using imaging-based flow cytometry, we found that IFNγ treatment shifts the lipid raft polarity of WT but not Bst2−/− hematopoietic stem and progenitor cells (HSPCs). Furthermore, RNAseq analysis, reverse phase protein array and western blot analysis of HSPCs indicate that BST2 promotes ERK1/2 phosphorylation during IFNγ-mediated stress. Overall, we find that BST2 facilitates HSC division by promoting cell polarization and ERK activation, thus elucidating a key mechanism of interferon-dependent HSPC activation. These findings inform future approaches in the treatment of cancer and bone marrow failure.