Asthma is a chronic inflammatory disease of the airways where T cells manifest a biased Th2/Th17 differentiation and a hyperactive phenotype. The latter is associated with sustained intracellular signaling. Signaling processes are usually transient due to negative homeostatic regulation. There is a knowledge gap in our understanding of mechanisms that induce sustained signaling. We propose to delineate the mechanism of induction of sustained signaling in T cells from asthma. We have reported that the signaling molecule sprouty 2 (spry 2) plays an essential role in establishing a self-sustained signaling mechanism for ERK1/2. To address this further we have generated CD4 targeted spry 2 knockout mice. Spry2-/- T cells have increased Cbl-b and decreased Nedd4. The foregoing ubiquitin ligases antagonistically regulate TCR ubiquitylation, endocytosis, degradation and thereby, control TCR signaling output. As a consequence of these receptor proximal abnormalities spry2-/-T cells have impaired signaling and proliferation. These impairments become more pronounced following CD28 engagement. Spry2-/- T cells have impaired Th2/Th17 differentiation. They are unable to mount airway inflammation, hyperreactivity and remodeling in a mouse model of asthma. Based upon these preliminary results we hypothesize that spry 2 amplifies and prolongs T cell signaling by forming a tripartite regulatory network where spry 2 and Nedd4 antagonize the signal terminating action of Cbl-b. Spry2- driven amplification and sustenance of signaling is important for co-stimulation, Th2/Th17 differentiation and development of asthma.
Under specific aim 1 we will examine the role of spry 2 in generating sustained signaling in T cells. We will define the scope of CD3- and especially CD28-induced signaling pathways that are regulated by spry 2. We will examine the contribution of Cbl-b and Nedd4 to the spry2 knockout phenotype.
Specific aim 2 will study the importance of spry 2 for Th2 and Th17 cell differentiation in vitro and in vivo in spry2-/- mice. We will delineate the signaling mechanism by which spry 2 regulates Th2/Th17 differentiation.
Under specific aim 3 we will delineate the role of spry 2 in inducing and sustaining inflammation in a mouse model of chronic asthma. We will examine if Cbl-b knockout reverses the spry2 knockout phenotype.
Under specific aim 4 we will study the expression of spry 2 in CD4 T cells from asthmatic patients and examine its contribution to the hyperactive T cell phenotype and biased differentiation in asthma. These studies are important because they have uncovered a hitherto unknown regulatory network involving spry2, Cbl-b and Nedd4, which controls Th2/Th17 differentiation and development of asthma.
Asthma is a major public health problem. This chronic illness is associated with persistent inflammation. The mechanism of persistence of inflammation is unknown. We will examine a novel mechanism that allows persistence of inflammation. The proposed studies will advance knowledge in our understanding of the mechanism of sustained activation of inflammatory cells and persistence of asthma. The outcome of this project will help develop novel therapeutic targets.
|Alam, Rafeul; Good, James; Rollins, Donald et al. (2017) Airway and serum biochemical correlates of refractory neutrophilic asthma. J Allergy Clin Immunol 140:1004-1014.e13|
|Verma, Mukesh; Liu, Sucai; Michalec, Lidia et al. (2017) Experimental asthma persists in IL-33 receptor knockout mice because of the emergence of thymic stromal lymphopoietin-driven IL-9+ and IL-13+ type 2 innate lymphoid cell subpopulations. J Allergy Clin Immunol :|
|Liu, Weimin; Liu, Sucai; Verma, Mukesh et al. (2017) Mechanism of TH2/TH17-predominant and neutrophilic TH2/TH17-low subtypes of asthma. J Allergy Clin Immunol 139:1548-1558.e4|
|Gelfand, Erwin W; Alam, Rafeul (2015) The other side of asthma: Steroid-refractory disease in the absence of TH2-mediated inflammation. J Allergy Clin Immunol 135:1196-8|
|Christianson, Christina A; Goplen, Nicholas P; Zafar, Iram et al. (2015) Persistence of asthma requires multiple feedback circuits involving type 2 innate lymphoid cells and IL-33. J Allergy Clin Immunol 136:59-68.e14|
|Alam, Rafeul (2015) Reply: To PMID 25042748. J Allergy Clin Immunol 135:291|
|Germinaro, Matthew; Reynolds, Paul; Knight, Vijaya et al. (2015) Association of B-cell activating factor receptor deficiency with the P21R polymorphism and common variable immunodeficiency. Ann Allergy Asthma Immunol 115:82-3|
|Schulten, Véronique; Tripple, Victoria; Sidney, John et al. (2014) Association between specific timothy grass antigens and changes in TH1- and TH2-cell responses following specific immunotherapy. J Allergy Clin Immunol 134:1076-83|
|Irvin, Chaoyu; Zafar, Iram; Good, James et al. (2014) Increased frequency of dual-positive TH2/TH17 cells in bronchoalveolar lavage fluid characterizes a population of patients with severe asthma. J Allergy Clin Immunol 134:1175-1186.e7|
|Alam, Rafeul (2014) Obesity and asthma--is there a causal association? Immunol Allergy Clin North Am 34:xi-xii|