Fine-tuning levels of filamins A and B as a specific mechanism sustaining Th2 lymphocyte functions

Abstract

Introduction

Asthma is a chronic inflammatory disease of lower airways that affects nearly 400 million people worldwide. Nearly half of asthmatic patients present a high type-2 inflammation characterized by a massive recruitment of T helper 2 (Th2) lymphocytes producing type 2 cytokines, eosinophilia and high levels of IgE. Treatments targeting type 2 cytokines and their receptors but also targeting IgE are already used in clinics. An attractive therapy would consist in targeting the recruitment of Th2 lymphocytes to inflammatory sites. We previously showed that the ASB2 gene that encodes the specificity subunit of an E3 ubiquitin ligase belongs to the core set of Th2-specific genes (Cancer Immunol Res 2019.7: 1332–1344).

Methods

ASB2 knockout mice and small molecules were used to modulate the levels of ASB2α and its substrates, filamins a and b (FLNa/b), in mouse primary Th2 lymphocytes and/or PBMC from healthy donors. In vitro experiments including global transcriptomic and proteomic approaches, high content and live imaging, as well as several immunological techniques were used to decipher the role of ASB2α in Th2 lymphocytes. In vivo mouse models of airway inflammation and asthma were used to investigate the role of the ASB2α in type 2 inflammation and determine whether the ASB2α-FLNa/b axis represents a therapeutic opportunity in Th2-driven diseases.

Results

Here, we show that ASB2α triggers ubiquitylation and proteasomal degradation of FLNa/b in Th2 lymphocytes. As a consequence, Th2 lymphocytes exhibit lower levels of FLNa/b proteins compared to naïve CD₄ ⁺ T lymphocytes or other T helper subsets, associated with an elongated shape and a specific dynamic migration pattern depending on integrin αVß3 activation. Furthermore, we show decreased recruitment of Th2 lymphocytes in inflamed lungs of ASB2α-deficient mice submitted to ovalbumin or house dust mite induced airway inflammation, associated with decreased eosinophilia and decreased type 2 cytokine production. Using a model of passive asthma that relies on the injection of ovalbumin-specific Th2 lymphocytes and ovalbumin inhalations, we show that mice that received ASB2α-deficient or accumulating FLNa/b Th2 lymphocytes exhibit decreased airway inflammation but also mucus secretion and remodeling of the airways compared to mice receiving control Th2 lymphocytes.

Conclusion

In conclusion, our study highlights the key role of a fine regulation of FLNa/b levels in Th2 lymphocyte functions as a driver of Th2-dependent airway inflammation. Our results show that augmenting FLNa/b levels in Th2 lymphocytes benefits in asthma features, indicating that ASB2α and its substrates FLNa/b may represent novel pharmacological targets in type 2 pathologies (Preprint (v1) Res. Square, [https://doi.org/10.21203/rs.3.rs-3878460/v1]).