Suppressor of Cytokine Signaling (SOCS)1 Regulates Interleukin-4 (IL-4)-activated Insulin Receptor Substrate (IRS)-2 Tyrosine Phosphorylation in Monocytes and Macrophages via the Proteasome

Abstract

Allergic asthma is a chronic lung disease initiated and driven by Th2 cytokines IL-4/-13. In macrophages, IL-4/-13 bind IL-4 receptors, which signal through insulin receptor substrate (IRS)-2, inducing M2 macrophage differentiation. M2 macrophages correlate with disease severity and poor lung function, although the mechanisms that regulate M2 polarization are not understood. Following IL-4 exposure, suppressor of cytokine signaling (SOCS)1 is highly induced in human monocytes. We found that siRNA knockdown of SOCS1 prolonged IRS-2 tyrosine phosphorylation and enhanced M2 differentiation, although siRNA knockdown of SOCS3 did not affect either. By co-immunoprecipitation, we found that SOCS1 complexes with IRS-2 at baseline, and this association increased after IL-4 stimulation. Because SOCS1 is an E3 ubiquitin ligase, we examined the effect of proteasome inhibitors on IL-4-induced IRS-2 phosphorylation. Proteasomal inhibition prolonged IRS-2 tyrosine phosphorylation, increased ubiquitination of IRS-2, and enhanced M2 gene expression. siRNA knockdown of SOCS1 inhibited ubiquitin accumulation on IRS-2, although siRNA knockdown of SOCS3 had no effect on ubiquitination of IRS-2. Monocytes from healthy and allergic individuals revealed that SOCS1 is induced by IL-4 in healthy monocytes but not allergic cells, whereas SOCS3 is highly induced in allergic monocytes. Healthy monocytes displayed greater ubiquitination of IRS-2 and lower M2 polarization than allergic monocytes in response to IL-4 stimulation. Here, we identify SOCS1 as a key negative regulator of IL-4-induced IRS-2 signaling and M2 differentiation. Our findings provide novel insight into how dysregulated expression of SOCS increases IL-4 responses in allergic monocytes, and this may represent a new therapeutic avenue for managing allergic disease.Allergic asthma is an immune disorder characterized by elevation of total and specific IgE and infiltration of monocytes, lymphocytes, mast cells, eosinophils, and basophils in the lungs that causes inflammation and wheezing, cough, and dyspnea (1-4). A complex interplay of genetic and environmental factors contributes to the onset and maintenance of these diseases. Mechanistically, it is known that cytokines secreted from Th2 cells, such as interleukin (IL)-4, IL-5, IL-9, and IL-13, have a pivotal role in dictating the pathology of allergic disease (1, 2, 5, 6). The pathways by which IL-4 and IL-13 exert their biological effects have been a major focus of research and development of therapeutics to block their action through type I and II IL-4 receptors. Previously, we showed that in macrophages, IL-4 engagement of the type I IL-4 receptor resulted in robust tyrosine phosphorylation of insulin receptor substrate (IRS)-2, recruitment of p85 regulatory subunit of PI3K and GRB2, and strong induction of a subset of hallmark M2, also known as M(IL-4) (7), macrophage genes (8, 9). In contrast, IL-13 binding to the type II receptor resulted in only modest IRS-2 phosphorylation. Increasing the concentration of IL-13 did n...

Mechanisms of Dupilumab

“…In addition to STAT6 activation, the IL‐4R complexes activate other signalling pathways that contribute to the regulation of allergic responses. One pathway involves the binding of the insulin receptor substrate 1/2 (IRS1/2) proteins at Y500 of the human IL‐4Rα, which then act to link the IL‐4R with several downstream signalling pathways, most notably the phosphoinositide 3‐kinases (PI3K)‐AKR mouse thymoma kinase (AKT) axis, relevant to M2 macrophage activation (Figure ). The latter appears to proceed via a PI3K‐ mTORC2 axis that activates the transcription factor IRF4 .…”

“…The latter appears to proceed via a PI3K‐ mTORC2 axis that activates the transcription factor IRF4 . In turn, IRS2‐dependent signalling is negatively regulated by suppressor of cytokine signalling 1 (Socs1)‐dependent ubiquitination (Figure ). Notwithstanding these results, a negative regulatory function of the IRS‐2 pathway in regulating the allergic response has been demonstrated using in vivo genetic approaches.…”

Nobiletin inhibits invasion via inhibiting AKT/GSK3β/β-catenin signaling pathway in Slug-expressing glioma cells

“…Chromatin immunoprecipitation (ChIP) assay. ChIP assay was performed as previously described with slight modification (17). β-catenin antibody was used, and qPCR was performed with specific primers to the slug promoter.…”

Nuclear Localization of Suppressor of Cytokine Signaling-1 Regulates Local Immunity in the Lung

“…They suggest that regulation of SOCS1 mainly affects hematopoietic cells, not epithelial cells. McCormick et al showed that reduced expression of SOCS1 has been shown to prolong IL-4-induced IRS-2 tyrosine phosphorylation and enhanced M2 differentiation (72). IRS-2 also plays a major role in allergic lung inflammation and remodeling (73).…”