Interactome Networks of FOSL1 and FOSL2 in Human Th17 Cells.

Ankitha Shetty,Sanjeev Galande,Robert Moulder,Tanja Buchacher,Santosh D Bhosale,Subhash Kumar Tripathi,Rahul Biradar,Omid Rasool,Riitta Lahesmaa

doi:10.1021/acsomega.1c03681

Abstract

Dysregulated function of Th17 cells has implications in immunodeficiencies and autoimmune disorders. Th17 cell differentiation is orchestrated by a complex network of transcription factors, including several members of the activator protein (AP-1) family. Among the latter, FOSL1 and FOSL2 modulate the effector functions of Th17 cells. However, the molecular mechanisms underlying these effects are unclear, owing to the poorly characterized protein interaction networks of FOSL factors. Here, we establish the first interactomes of FOSL1 and FOSL2 in human Th17 cells, using affinity purification–mass spectrometry analysis. In addition to the known JUN proteins, we identified several novel binding partners of FOSL1 and FOSL2. Gene ontology analysis found a significant fraction of these interactors to be associated with RNA-binding activity, which suggests new mechanistic links. Intriguingly, 29 proteins were found to share interactions with FOSL1 and FOSL2, and these included key regulators of Th17 fate. We further validated the binding partners identified in this study by using parallel reaction monitoring targeted mass spectrometry and other methods. Our study provides key insights into the interaction-based signaling mechanisms of FOSL proteins that potentially govern Th17 cell differentiation and associated pathologies.

Highlights

Th17 cells are pro-inflammatory players that protect mucosal surfaces from extracellular pathogens
Th17 cell differentiation is initiated by the coordinated action of early expressed transcription factors (TFs), such as BATF, STAT3, and IRF4.9 This process is modulated by members of the activator protein (AP-1) family, which includes the JUN (JUNB10,11), FOS (FOSL1,12 FOSL29), and ATF (BATF,[13] ATF314) proteins
To study the interactomes of FOSL1 and FOSL2 in early Th17 cells, we first determined their expression in naive CD4+ T cells that were in vitro activated and differentiated toward Th17 fate for

Summary

Introduction

Th17 cells are pro-inflammatory players that protect mucosal surfaces from extracellular pathogens They can be derived in vitro by activating naive CD4+ T cells in the presence of IL-6, transforming growth factor-β (TGF-β), and interleukin (IL)1β (or IL-23). These cells are mainly characterized by the expression of IL-17A and IL17F; they secrete other cytokines, such as IL-21, IL-22, and GM-CSF.[1−6] Deficiency of Th17 cells causes susceptibility to mucocutaneous candidiasis,[7] whereas their uncontrolled activity can result in autoimmune conditions such as rheumatoid arthritis, multiple sclerosis, and systemic lupus erythematosus.[8] To investigate the incidence of these associated diseases and design suitable therapeutic measures, it is crucial to first understand the molecular basis of Th17 cell function. The molecular mechanisms that mediate these effects are not understood

Results

Discussion

Conclusion