Oxysterols direct immune cell migration via EBI2

Abstract

Epstein-Barr virus (EBV)-induced gene 2 (EBI2, aka GPR183) is a G protein-coupled receptor that is required for humoral immune responses and polymorphisms in the receptor have been associated with inflammatory autoimmune diseases1-3. The natural ligand for EBI2 has been unknown. Here we describe identification of 7α, 25-dihydroxycholesterol (5-cholesten-3β, 7α, 25-triol; 7α, 25-OHC) as a potent and selective agonist of EBI2. Functional activation of EBI2 by 7α, 25-OHC and closely related oxysterols was verified by monitoring second messenger readouts and saturable, high affinity radioligand binding. Furthermore we find that 7α, 25-OHC and closely related oxysterols act as chemoattractants for immune cells expressing EBI2 by directing cell migration in vitro and in vivo. A key enzyme required for the generation of 7α, 25-OHC is cholesterol 25-hydroxylase (Ch25h)4. Similar to EBI2 receptor knockout mice, mice deficient in Ch25h fail to position activated B cells within the spleen to the outer follicle and mount a reduced plasma cell response after an immune challenge. This demonstrates that Ch25h generates EBI2 bioactivity in vivo and suggests that the EBI2 − oxysterol signaling pathway plays an important role in the adaptive immune response.

Oxysterols and EBI2 promote osteoclast precursor migration to bone surfaces and regulate bone mass homeostasis

“…EBI2, like many other GPCRs, is internalized upon binding to cognate ligands (Hannedouche et al, 2011), although the internalization mechanism has not been defined. Autocrine EBI2 signaling and receptor internalization provide additional cell-intrinsic mechanisms for regulating OCP movement toward bone surfaces.…”

“…However, systemic RANKL administration has been shown to increase OCP homing back to BM and to promote local OC differentiation (Kotani et al, 2013). These studies suggest that OCP movement in and out of BM tissue is highly regulated and that balanced responsiveness to B lymphocyte migration in secondary lymphoid organs (Gatto et al, 2009(Gatto et al, , 2013Pereira et al, 2009b;Hannedouche et al, 2011;Kelly et al, 2011;Liu et al, 2011;Yi and Cyster, 2013), in controlling monocyte and OCP movement and positioning within BM. We show that EBI2 is highly expressed in OCPs and mature OCs and promotes OCP motility in vitro and in various chemoattractants regulates OCP movement and differentiation.…”

“…EBI2 signaling in OCPs in vivo. EBI2 is sensitive to ligandinduced receptor internalization (Hannedouche et al, 2011). Thus, we considered the possibility that autocrine EBI2 signaling in OCPs attenuates the sensing of EBI2 ligand gradients in vivo.…”

“…EBI2 and its oxysterol ligands control immune cell migration (Gatto et al, 2009;Pereira et al, 2009bPereira et al, , 2010aHannedouche et al, 2011;Liu et al, 2011). We hypothesized that EBI2 promotes BMDM and OCP migration, thereby influencing cell-cell interaction and cell fusion.…”

Naive B-cell trafficking is shaped by local chemokine availability and LFA-1–independent stromal interactions

“…[8][9][10] Naive B cells also express moderate levels of Ebi2 (ie, GPR183), a GPCR binding 7a,25-dihydroxycholesterol (7a,25-OHC) produced by the cholesterol 25-hydroxylase (CH25H) and that mediates accumulation of B cells to the outer rim of B-cell follicles. [11][12][13][14] Despite these insights, there are remarkably few data that describe how chemokine receptors control active B-cell motility within lymphoid tissue. Since naive B cells express chemokine receptors for both the T-cell area and B-cell follicles, an attractive hypothesis is that the balanced responsiveness to CCR7 ligands of the T-cell area and CXCL13 in B-cell follicles shapes dynamic B-cell motility and restrains entry of CXCR5 2/2 B cells into follicles.…”