Abstract Despite extensive research, asthma remains a difficult to treat disease with staggering economic costs. Mechanisms in different asthmatic endotype are poorly understood. Posttranscriptional gene regulation by RNA- binding proteins (RBPs) and microRNAs (miRNAs) is increasingly recognized as important control mechanisms for pro-inflammatory genes but is understudied. RBPs, such as HuR (Elavl1), tristetraprolin (TTP) family members which bind to mRNA AU-rich elements (ARE), play critical roles in regulating mRNA stability and expression of key pro-inflammatory genes in asthma. HuR is a stabilizer RBP, whereas TTP family members are destabilizer RBPs. Due to the discordance between steady-state mRNA levels and protein, purely transcriptomic approaches may overlook critical inflammatory genes regulated by RBPs such as HuR and TTP. Yet, much of immunity and inflammation is controlled at the posttranscriptional level by RBPs and miRNAs. Many cytokine genes in CD4+ T cells are controlled by the balance between HuR and TTP family members. The field cannot move forward unless we better understand how RBPs posttranscriptionally regulate pro-inflammatory gene expression in different asthmatic endotypes. Our long-term goal is to understand posttranscriptional gene regulation in different endotypes of asthmatic airway inflammation. The objective of this application, which is our next step in pursuit of that goal, is to determine how HuR and TTP family members competitively regulate HuR expression, which in turn controls CD4+ T produced cytokines in asthma. Our central hypothesis is that HuR overproduction in type 2 high asthma is driven by an imbalance between stabilizing and destabilizing RBPs acting upon Elavl1 mRNA to affect its stability and translation. Our data indicate that HuR is over-expressed in type 2 high asthmatic CD4+ T cells, compared with normal controls and non-type 2 high. Furthermore, we have shown that conditional HuR KO in T cells significantly ameliorates allergen-induced lung inflammation in murine models. We have also demonstrated that HuR inhibition blocks Th2/Th17 secretion in asthmatic CD4+ T cells. Up to the present, the field has focused mostly on downstream HuR targets genes. In contrast, HuR regulation is not as well understood. The rationale for this research is that the proposed research will enable us to identify molecular mechanisms which drive HuR over-production in the context of type 2 high asthmatic lung inflammation. We plan to test the central hypothesis and accomplish these objectives by the following two specific aims: 1) Determine normal mechanisms of HuR expression in airway inflammation; 2) Determine molecular mechanisms underlying HuR dysregulation in type 2 high asthma. At the completion of the proposed research, our expected outcomes are to identify how HuR and TTP cooperate to normally control HuR expression and how they become dysfunctional in type 2 high asthmatic CD4+ T cells. These results are expe...