Discovery of an exosite on the SOCS2-SH2 domain that enhances SH2 binding to phosphorylated ligands

Suppressor of cytokine signaling (SOCS)2 protein is a key negative regulator of the growth hormone (GH) and Janus kinase (JAK)-Signal Transducers and Activators of Transcription (STAT) signaling cascade. The central SOCS2-Src homology 2 (SH2) domain is characteristic of the SOCS family proteins and is an important module that facilitates recognition of targets bearing phosphorylated tyrosine (pTyr) residues. Here we identify an exosite on the SOCS2-SH2 domain which, when bound to a non-phosphorylated peptide (F3), enhances SH2 affinity for canonical phosphorylated ligands. Solution of the SOCS2/F3 crystal structure reveals F3 as an α-helix which binds on the opposite side of the SH2 domain to the phosphopeptide binding site. F3:exosite binding appears to stabilise the SOCS2-SH2 domain, resulting in slower dissociation of phosphorylated ligands and consequently, enhances binding affinity. This biophysical enhancement of SH2:pTyr binding affinity translates to increase SOCS2 inhibition of GH signaling

Mediators of lifestyle behaviour changes in obese pregnant women. Secondary analyses from the DALI lifestyle randomised controlled trial

A better understanding of what drives behaviour change in obese pregnant overweight women is needed to improve the effectiveness of lifestyle interventions in this group at risk for gestational diabetes (GDM). Therefore, we assessed which factors mediated behaviour change in the Vitamin D and Lifestyle Intervention for GDM Prevention (DALI) Lifestyle Study. A total of 436 women, with pre-pregnancy body mass index ≥29 kg/m 2 , ≤19 + 6 weeks of gestation and without GDM, were randomised for counselling based on motivational interviewing (MI) on healthy eating and physical activity, healthy eating alone, physical activity alone, or to a usual care group. Lifestyle was measured at baseline, and at 24–28 and 35–37 weeks of gestation. Outcome expectancy, risk perception, task self-efficacy and social support were measured at those same time points and considered as possible mediators of intervention effects on lifestyle. All three interventions resulted in increased positive outcome expectancy for GDM reduction, perceived risk to the baby and increased task self-efficacy. The latter mediated intervention effects on physical activity and reduced sugared drink consumption. In conclusion, our MI intervention was successful in increasing task self-efficacy, which was related to improved health behaviours

State of the structure address on MET receptor activation by HGF

The MET receptor tyrosine kinase (RTK) and its cognate ligand hepatocyte growth factor (HGF) comprise a signaling axis essential for development, wound healing and tissue homeostasis. Aberrant HGF/MET signaling is a driver of many cancers and contributes to drug resistance to several approved therapeutics targeting other RTKs, making MET itself an important drug target. In RTKs, homeostatic receptor signaling is dependent on autoinhibition in the absence of ligand binding and orchestrated set of conformational changes induced by ligand-mediated receptor dimerization that result in activation of the intracellular kinase domains. A fundamental understanding of these mechanisms in the MET receptor remains incomplete, despite decades of research. This is due in part to the complex structure of the HGF ligand, which remains unknown in its full-length form, and a lack of high-resolution structures of the complete MET extracellular portion in an apo or ligand-bound state. A current view of HGF-dependent MET activation has evolved from biochemical and structural studies of HGF and MET fragments and here we review what these findings have thus far revealed

Structure and Functional Characterization of the Conserved JAK Interaction Region in the Intrinsically Disordered N‑Terminus of SOCS5

SOCS5 can negatively regulate both JAK/STAT and EGF-receptor pathways and has therefore been implicated in regulating both the immune response and tumorigenesis. Understanding the molecular basis for SOCS5 activity may reveal novel ways to target key components of these signaling pathways. The N-terminal region of SOCS5 coordinates critical protein interactions involved in inhibition of JAK/STAT signaling, and a conserved region within the N-terminus of SOCS5 mediates direct binding to the JAK kinase domain. Here we have characterized the solution conformation of this conserved JAK interaction region (JIR) within the largely disordered N-terminus of SOCS5. Using nuclear magnetic resonance (NMR) chemical shift analysis, relaxation measurements, and NOE analysis, we demonstrate the presence of preformed structural elements in the JIR of mouse SOCS5 (mSOCS5_175–244), consisting of an α-helix encompassing residues 224–233, preceded by a turn and an extended structure. We have identified a phosphorylation site (Ser211) within the JIR of mSOCS5 and have investigated the role of phosphorylation in modulating JAK binding using site-directed mutagenesis

Elevated cytokine and chemokine production in lungs of <i>Socs4^R108X/R108X</i> is associated with an increased influx of T cells.

<p>(A) Cytokine and chemokine levels were analysed by ELISA and Bioplex in lung homogenates at day 3 post-infection with X31 virus. Mean data ± S.E.M. are shown for biological replicates (n = 4 for Balb/c, n = 5 for <i>Socs4^R108X/R108X</i>), * indicates p<0.05, **<0.005. (B) Phenotypic analysis of lung hematopoietic subsets in <i>Socs4^R108X/R108X</i> and Balb/c mice at day 3 post-infection. Flow cytometry analysis was performed on homogenized lungs and extracted BAL. Data plotted include combined cell numbers from lungs and BAL, * indicates p<0.05, **<0.005. (C) Expression of <i>Socs4</i> mRNA in immune cells recovered from BAL and in the lungs of Balb/c mice infected with X31 virus. Mean data ± S.E.M. are shown for n = 3 biological replicates, u/inf = uninfected.</p

Reduced downregulation of CD62L expression on <i>Socs4^R108X/R108X</i> CD8 cells in following X31 influenza infection.

<p>(A) Flow cytometric analysis showing the gating strategy and percentages of CD62L^hi and CD62L^l°CD8 T cells on day 5 post-infection with X31 influenza virus. Representative dot plots are shown from control Balb/c and <i>Socs4^R108X/R108X</i> mice. (B) Total CD8 T cell numbers in the lymph node (MLN), lungs (BAL) and spleen (SPL) of <i>Socs4^R108X/R108X</i> and Balb/C mice on day d5, d6 and d7 following infection with X31 influenza virus. (C) Total number and percentages of CD62L^hi and CD62L^l°CD8 cells in the MLN of <i>Socs4^R108X/R108X</i> and Balb/C mice following X31 influenza virus infection.</p

Altered tissue distribution of virus-specific CD8 T cells in <i>Socs4^R108X/R108X</i> mice.

<p>(A) Total numbers (BAL+MLN+SPL) of virus-specific (K^dNP₁₄₇ positive) CD8 T cells following X31 influenza virus infection. Mean values (n = 5) are plotted, error bars represent SEM. (B) Significant differences were observed in the distribution of K^dNP₁₄₇ positive CD8 T cells in lungs (BAL) and spleens of <i>Socs4^R108X/R108X</i> and Balb/c control mice following infection. *p<0.05, **<0.005, ***<0.001 (C) Percentage of GzmB positive K^dNP₁₄₇ positive CD8 T cells in various tissues on d10 post-infection (left hand panel); percentage of CD107a positive (middle panel) or GzmB positive (right hand panel) IFN-γ positive CD8 T cells on d10 post-infection following <i>ex vivo</i> stimulation with K^dNP₁₄₇ peptide. Mean values (n = 5) are plotted, error bars represent SD.</p

Defective TCR responses in <i>Socs4^R108X/R108X</i> CD8 T cells.

<p>CD4 or CD8 T cells were purified from <i>Socs4^R108X/R108X</i> or wild-type spleens by negative selection, plated onto anti-CD3 coated plates in the presence of IL-2 and analysed at the indicated timepoints. (A) Q-PCR analysis showing increased expression of <i>Socs4</i> mRNA in purified T cells from Balb/c mice following TCR engagement (mean±SEM, n = 3). (B) Cells were analysed by flow cytometry for the expression of the T cell activation marker, CD62L (mean±S.D.), n = cells derived from 3 mice. (C–D) Cells were labelled with Cell Trace Violet (CTV) for analysis of proliferative responses. Cell numbers per division are shown in the left hand panels; total cell numbers in the centre panels, (C) CD4 T cells, (D) CD8 T cells. Results are shown as the mean±S.E.M. using pooled data from 2 independent experiments (n = 5 mice per group per experiment). Representative histograms are plotted for each subset (day 4; right hand panels).</p

Suppressor of cytokine signaling (SOCS)5 ameliorates influenza infection via inhibition of EGFR signaling

Influenza virus infections have a significant impact on global human health. Individuals with suppressed immunity, or suffering from chronic inflammatory conditions such as COPD, are particularly susceptible to influenza. Here we show that suppressor of cytokine signaling (SOCS) five has a pivotal role in restricting influenza A virus in the airway epithelium, through the regulation of epidermal growth factor receptor (EGFR). Socs5-deficient mice exhibit heightened disease severity, with increased viral titres and weight loss. Socs5 levels were differentially regulated in response to distinct influenza viruses (H1N1, H3N2, H5N1 and H11N9) and were reduced in primary epithelial cells from COPD patients, again correlating with increased susceptibility to influenza. Importantly, restoration of SOCS5 levels restricted influenza virus infection, suggesting that manipulating SOCS5 expression and/or SOCS5 targets might be a novel therapeutic approach to influenza. DOI: http://dx.doi.org/10.7554/eLife.20444.00