Rhoh Is a Negative Regulator of Eosinophilopoiesis
Total Page:16
File Type:pdf, Size:1020Kb
Cell Death and Differentiation (2016) 23, 1961–1972 & 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved 1350-9047/16 www.nature.com/cdd RhoH is a negative regulator of eosinophilopoiesis Christina Stoeckle1,3, Barbara Geering1,4, Shida Yousefi1,SašaRožman1, Nicola Andina1, Charaf Benarafa2 and Hans-Uwe Simon*,1 Eosinophils are frequently elevated in pathological conditions and can cause tissue damage and disease exacerbation. The number of eosinophils in the blood is largely regulated by factors controlling their production in the bone marrow. While several exogenous factors, such as interleukin-5, have been described to promote eosinophil differentiation, comparatively little is known about eosinophil-intrinsic factors that control their de novo generation. Here, we report that the small atypical GTPase RhoH is induced during human eosinophil differentiation, highly expressed in mature blood eosinophils and further upregulated in patients suffering from a hypereosinophilic syndrome. Overexpression of RhoH increases, in a Rho-associated protein kinase- dependent manner, the expression of GATA-2, a transcription factor involved in regulating eosinophil differentiation. In RhoH−/− mice, we observed reduced GATA-2 expression as well as accelerated eosinophil differentiation both in vitro and in vivo. Conversely, RhoH overexpression in bone marrow progenitors reduces eosinophil development in mixed bone marrow chimeras. These results highlight a novel negative regulatory role for RhoH in eosinophil differentiation, most likely in consequence of altered GATA-2 levels. Cell Death and Differentiation (2016) 23, 1961–1972; doi:10.1038/cdd.2016.73; published online 14 October 2016 Eosinophils are short-lived effector and regulatory cells that their interaction partners or competitors. For example, are increasingly recognized as having key roles in the while GATA-2 expression is required for the proper differentia- immune system, including maintenance of long-term antibody tion of several haematopoietic lineages, including eosino- responses and defence against bacteria and viruses.1,2 On phils,8 high GATA-2 expression inhibits HPC proliferation.9,10 the other hand, their potentially destructive nature becomes Similarly, overexpression of GATA-2 in progenitor cells in the apparent in a number of eosinophilic diseases such as presence of C/EBPα drives eosinophil differentiation, while hypereosinophilic syndromes (HES), diseases characterized it promotes mast cell/basophil generation in the absence of by eosinophil-mediated tissue damage and organ dysfunc- C/EBPα.11 Furthermore, while GATA-2 induces the expres- tion.3,4 Eosinophils contribute to disease pathology directly sion of eosinophil-derived neurotoxin, it also antagonizes and indirectly by releasing cytotoxic molecules and by sup- GATA-1-mediated expression of other eosinophil-related porting an ongoing inflammation.1 Besides HES, eosinophilia genes, including major basic protein.12–14 These apparently can be observed in a wide range of infectious, allergic and discordant findings highlight the need for a better under- autoimmune diseases, as well as in cancer.3,5 Given the standing of the molecular mechanisms controlling eosinophil increasing incidence of such diseases and the often unsa- differentiation. tisfactory treatment options available, it is of considerable The best studied cytokines promoting eosinophil develop- importance to better understand factors governing eosinophil ment are interleukin (IL)-3, IL-5, and granulocyte/macrophage biology under both normal and inflammatory conditions. colony-stimulating factor (GM-CSF).6 In addition to their role in Eosinophil numbers are largely regulated by their produc- eosinophilopoiesis, they also enhance eosinophil survival.15 tion in the bone marrow where they differentiate from myeloid Of these eosinophil hematopoietins, IL-5 is the most specific precursors.6 Lineage commitment is controlled by GATA-1, for the eosinophil lineage. Transgenic overexpression of IL-5 in GATA-2, PU.1 and c/EBP transcription factors. For instance, mice results in eosinophilia, whereas deletion of the IL-5 gene mice lacking GATA-1 or c/EBP expression are devoid of strongly reduces eosinophil counts in blood and lungs eosinophils, and transduction of hematopoietic progenitor following allergen challenge.6,16 Furthermore, many eosino- cells (HPC) with either of these genes promotes differentiation philic diseases are associated with increased IL-5 levels.3,17 into eosinophils.7 However, the situation is not always These findings together with the knowledge of the critical role straightforward. Lineage specification and maturation strongly of IL-5 for eosinophil generation and survival have prompted depend on the relative levels of these transcription factors and the development of therapeutic anti-IL-5 and anti-IL-5 receptor 1Institute of Pharmacology, University of Bern, Bern, Switzerland and 2Theodor Kocher Institute, University of Bern, Bern, Switzerland *Corresponding author: HU Simon, Institute of Pharmacology, University of Bern, Inselspital, INO-F, CH-3010 Bern, Switzerland. Tel: +41 31 632 3281; Fax: +41 31 632 4992; E-mail: [email protected] 3Current address: Novartis Institutes for Biomedical Research, Novartis Pharma AG, Basel, Switzerland 4Current address: Roche Pharma Research & Early Development, Roche Innovation Center Basel, Basel, Switzerland Abbreviations: ECP, eosinophil cationic protein; EDN, eosinophil-derived neurotoxin; FACS, fluorescence-activated cell sorting; Flt3L, Fms-related tyrosine kinase 3 ligand; G-CSF, granulocyte colony-stimulating factor; GM-CSF, granulocyte/macrophage colony-stimulating factor; HES, hypereosinophilic syndrome; HPC, hematopoietic progenitor cells; 4-OHT, 4-hydroxytamoxifen; IL, interleukin; MEK, mitogen/extracellular signal-regulated kinase; PBMC, peripheral blood mononuclear cells; PCR, polymerase chain reaction; PI3K, phosphoinositide 3-kinase; ROCK, Rho-associated protein kinase; SCF, stem cell factor; STAT, signal transducer and activator of transcription; WT, wild-type Received 11.1.16; revised 16.6.16; accepted 27.6.16; Edited by P Salomoni; published online 14 October 2016 RhoH in eosinophil differentiation C Stoeckle et al 1962 n o i s s e r p x e Monocytes Neutrophils Eosinophils NK cells PBMC T cells Bcells A N 20 RhoH R m e 38 GAPDH v i t a l e R Eosinophils + IL-5 0 2h 3h 18h 24h -IL-5 IL-3 GM-CSF 20 RhoH 20 RhoH 38 GAPDH 38 GAPDH Healthy HES HES eosinophils + IL-5 donors patients 0 2h 3h 18h 24h 20 RhoH 86 20 RhoH 79 p-STAT3 38 GAPDH 38 GAPDH Figure 1 RhoH expression in peripheral blood eosinophils. Leukocyte subsets were isolated from peripheral blood and RhoH expression was measured by qPCR (a)or immunoblotting (b). Representative immunoblots of eosinophils from healthy donors stimulated with 10 ng/ml IL-5 (c) or 10 ng/ml of IL-5, IL-3 or GM-CSF for 3 h (d), freshly isolated eosinophils from healthy donors or HES patients (e), or IL-5 stimulated eosinophils from HES patients (f), are presented. Values in panel (a) represent means +/ − S.D. Data in panels (b–f) are representative for at least three independent experiments antibodies, which are currently being investigated in eosino- production in neutrophils,29 but its function in eosinophils is philic disorders.1,18 unknown. RhoH belongs to the family of small GTPases that are In this study, we report that RhoH deficiency promotes, and involved in diverse cellular processes, including signalling, RhoH overexpression reduces, eosinophil differentiation in vitro vesicle transport, migration, proliferation and differentiation. In and in vivo. Moreover, RhoH induces the developmentally contrast to most family members, RhoH is GTPase deficient important transcription factor GATA-2 through a Rho-associated and, therefore, its activity is assumed to be regulated at the protein kinase (ROCK)-dependent mechanism. In addition, level of protein expression rather than by switching between RhoH appears to promote cellular quiescence in a manner 10 active (GTP-bound) and inactive (GDP-bound) forms.19 RhoH similar to what has been reported for GATA-2. Furthermore, is exclusively expressed in the hematopoietic system and is our data suggest that IL-5 induces RhoH in immature mutated in a number of lymphomas and leukemias, but the eosinophils, a pathway that also remains functional following mechanisms by which dysregulated RhoH contributes to maturation. Taken together, our data suggest that IL-5 not only malignancy remain unclear. drives eosinophil differentiation, but also induces an inhibitory With respect to its physiological functions, RhoH is involved pathway limiting this process in which RhoH has a major role. in T-cell receptor (TCR) signalling, where it regulates the – subcellular localization of ZAP70 and LCK.20 22 Following Results TCR stimulation, RhoH is degraded.23 RhoH−/− mice have reduced T-cell numbers due to a failure of positive selection, RhoH is expressed in human eosinophils and upregu- 21,24 and impaired peripheral T-cell responses. This phenotype lated upon IL-5 stimulation. To investigate whether RhoH is is similar to that of two recently described natural RhoH- expressed in eosinophils under physiological conditions, we deficient siblings, in which impaired T-cell function resulted in isolated eosinophils from peripheral blood of healthy donors 25 susceptibility to certain viral infections. In mast cells, RhoH is and found that eosinophils expressed higher levels of RhoH critical for FcεRI-dependent