PU.1 is involved in the immune response to Aspergillus fumigatus through upregulating Dectin-1 expression.

Min Wang,Yi Shi,Zhicheng Liu,Quan Wang,Ting Wu,Feng Cai,Xin Su,Chenyang Liu

doi:10.1186/s12879-016-1632-x

Abstract

BackgroundInvasive aspergillosis is a life-threatening disease, and its incidence has increased in the recent past. Dectin-1 recognizes β-glucans and mediates innate immune responses to Aspergillus fumigatus. Transcription factor PU.1 has been the focus of recent research due to its role in inflammation and infection. However, its role in Dectin-1 regulation during A. fumigatus infection remains to be elucidated.MethodsTHP-1 cells were stimulated with A. fumigatus conidia. We then used real-time RT-PCR, Western blot, and immunofluorescence assays to analyze the mRNA and protein levels and cellular distribution, respectively, of Dectin-1 and PU.1 in stimulated THP-1 cells. Additionally, we used the luciferase reporter assays, chromatin immunoprecipitation (ChIP) assays, electrophoretic mobility shift assays (EMSA), and RNA interference experiments to investigate the role of PU.1 in Dectin-1 regulation.ResultsOur results revealed that Dectin-1 mRNA and protein levels as well as the PU.1 protein level were increased in THP-1 cells stimulated with A. fumigatus conidia, while the mRNA expression level did not significantly change between the stimulated and control groups. We also observed that PU.1 translocated into the nucleus in stimulated THP-1 cells. The results of the luciferase reporter assay showed that PU.1 promoted human Dectin-1 (hDectin-1) gene activity. ChIP and EMSA indicated that PU.1 could bind with hDectin-1 gene promoter at three potential transcription factor-binding sites (TFBSs). In addition, knockdown of PU.1 significantly decreased Dectin-1 expression.ConclusionsThis study demonstrated the novel role of PU.1 in the immune response to A. fumigatus through upregulation of Dectin-1 expression and its translocation to the nucleus in A. fumigatus-stimulated THP-1 cells.

Highlights

Invasive aspergillosis is a life-threatening disease, and its incidence has increased in the recent past
Dectin-1 and PU.1 mRNA and protein expression levels in A. fumigatus conidia-stimulated THP-1 cells In order to study the PU.1 and Dectin-1 expression patterns in the antifungal immune response, THP-1 cells were exposed to A. fumigatus conidia at an multiplicity of infection (MOI) of 1 for 2, 8, and 12 h
The results found that PU.1 mRNA levels remained unchanged in THP-1 cells; the PU.1 protein expression was higher in the stimulated cells than in the control cells (Fig. 1b and d)

Summary

Introduction

Invasive aspergillosis is a life-threatening disease, and its incidence has increased in the recent past. Dectin-1 recognizes β-glucans and mediates innate immune responses to Aspergillus fumigatus. Transcription factor PU. has been the focus of recent research due to its role in inflammation and infection. Its role in Dectin-1 regulation during A. fumigatus infection remains to be elucidated. Invasive aspergillosis (IA) is a life-threatening disease whose incidence is growing worldwide due to the increasing number of immunocompromised patients over the last decades [1]. The innate immune system serves as the first line of defense against fungal infection, as it is capable of recognizing and initiating an effective response to eliminate invading A. fumigatus [4]. There is limited knowledge of the regulation and detailed immune mechanism involved in the defense against A. fumigatus infection. Further investigation of the mechanism would help develop effective immunoprophylaxis and to improve patient prognosis

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Conclusion