Molecular mechanisms of posttranscriptional gene regulation in asthmatic airway inflammation

Asthma remains a difficult to treat disease that greatly impacts deployed military personnel and Veterans.
Currently used medications either: 1) are very expensive (biologics), placing enormous burdens on the VA
Healthcare System; 2) have significant side effects (oral steroids); or 3) do not work in some endotypes, e.g.,
steroid-resistant asthma. Due to discordance between steady-state mRNA levels and protein, transcriptomic
approaches may overlook genes regulated by RNA binding proteins (RBPs). Posttranscriptional gene regulation
by RBPs and microRNAs (miRNAs) is increasingly recognized as an important control mechanism for pro-
inflammatory genes but understudied. RBPs, such as HuR (Elavl1), which binds to mRNA AU-rich elements
(AREs), play critical roles by regulating mRNA stability and translation of key pro-inflammatory gene expression
in asthma. Our recently published data indicates that HuR ablation in mice ameliorates allergen-driven lung
inflammation. Furthermore, HuR is over-expressed in asthmatic CD4+ T cells and its inhibition reduces cytokine
expression. Using RNA Immunoprecipitation techniques (RIP-seq) combined with genetically engineered murine
models, we have demonstrated that HuR controls both Th2 and Th17 CD4+ T lineages. Without a better
understanding of posttranscriptional control of inflammation, the field will continue to have a limited insight into
molecular mechanisms, which likely contribute to asthma endotypes and unequal treatment responses and
outcomes in patients. Our long-term goal is to understand posttranscriptional gene regulation in different
endotypes of asthmatic airway inflammation. The objective of this application is to determine how HuR and TTP
family members regulate key pro-inflammatory molecules produced by CD4+ T cells in different asthma
endotypes. Our rationale is that investigation of HuR-driven gene expression will identify molecular mechanisms
that differ between asthma endotypes, especially type 2-high vs. non-type 2-high. The central hypothesis is
that the HuR-Gata3 interaction in CD4+ T cells controls airway inflammation in type 2-high asthma (driven by
Gata3) and in non-type 2-high asthma (driven by Il17). We plan to test the central hypothesis and accomplish
these objectives by the following three specific aims: 1) Define molecular mechanisms of HuR regulation in
murine models of type 2-high airway inflammation; 2) Elucidate human CD4+ T cell gene clusters permissive for
asthmatic lung inflammation and 3) Determine effects of HuR inhibition on T cell-mediated inflammation in type
2 high and non-type 2 high asthma. At the completion of the proposed research, our expected outcomes are to
identify how HuR controls CD4+ T cell differentiation and function, which are critical for the development of
allergic airway inflammation. These results are anticipated to have a sustained positive impact upon the field
because they will further define molecular mechanisms distinguishing type 2 high from non-type 2 high asthma
endotypes. The fundamentally important knowledge gained will provide opportunities to develop novel therapies
to treat asthmatic lung inflammation by interfering with HuR function, including in steroid-resistant asthma.

Grant Number: 5I01CX002491-02
NIH Institute/Center: VA
Principal Investigator: ULUS ATASOY