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The JAK-STAT Signaling Pathway

Several cytokine receptors have tightly bound Janus kinase or JAK proteins attached at their cytosolic tail. Small signaling molecules such as cytokines, growth hormones, or prolactins bind to the cytokine receptors and initiate their dimerization. The dimerization brings the cytosolic JAKs together that trans-phosphorylate and activates each other. The activated JAKs now phosphorylate cytosolic tails of the cytokine receptors, which serve as binding sites for adaptor proteins such as  SH2...
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Related Experiment Video

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A TIRF Microscopy Technique for Real-time, Simultaneous Imaging of the TCR and its Associated Signaling Proteins
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A TIRF Microscopy Technique for Real-time, Simultaneous Imaging of the TCR and its Associated Signaling Proteins

Published on: March 22, 2012

Beyond dimerization: a membrane-dependent activation model for interleukin-4 receptor-mediated signalling.

Thomas Weidemann1, Siegfried Höfinger, Kurt Müller

  • 1Innovative Screening Technologies, Novartis Institutes for BioMedical Research, Brunnerstr 59, A-1235 Vienna, Austria. tj.weidemann@web.de

Journal of Molecular Biology
|January 16, 2007
PubMed
Summary

This study explores how cytokine receptors, like the interleukin-4 receptor (IL-4R), activate in the cell membrane. Researchers propose a new mechanism involving a rotational switch in the extracellular domain of the receptor. The membrane-proximal stem-loop region contains key elements of this switch. The WSXWS motif interacts with the lipid bilayer's surface, suggesting a functional role in activation. By analyzing interfacial energies of amino acid side-chains, the team suggests this motif may influence receptor conformation. This model could help design better biophysical assays for studying receptor function. The findings are specific to class I cytokine receptors, with the IL-4R as a model system.

Keywords:
cytokine receptor activationIL-4R signalingmembrane-proximal stem-loopWSXWS motif function

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Static Adhesion Assay for the Study of Integrin Activation in T Lymphocytes
09:14

Static Adhesion Assay for the Study of Integrin Activation in T Lymphocytes

Published on: June 13, 2014

Area of Science:

  • Cell signaling pathways in immunology
  • Structural biology of cytokine receptors
  • Membrane biophysics in receptor activation

Background:

Cytokine receptors are essential for transmitting signals that regulate cell growth and differentiation. Prior research has shown that these receptors function as class I receptors, transferring signals from outside to inside the cell. However, a unified mechanism for how these receptors activate in the membrane remains unclear. Established knowledge includes the role of dimerization in receptor function. Yet, no prior work had resolved the exact role of membrane interactions in this process. This gap motivated researchers to investigate the structural dynamics of these receptors. The interleukin-4 receptor (IL-4R) was selected as a model system. The lipid bilayer's influence on receptor activation is not well understood. This study aims to address that uncertainty by focusing on the extracellular domain's structure.

Purpose Of The Study:

The study aimed to explore how membrane interactions influence cytokine receptor activation. Specifically, it focused on the IL-4R as a model for class I cytokine receptors. The goal was to identify structural elements involved in receptor activation. Researchers proposed that the membrane-proximal region of the receptor plays a key role. This work sought to clarify the functional role of conserved motifs like WSXWS. The lipid bilayer's effect on receptor conformation was a central question. By analyzing interfacial energies, the team aimed to propose a new activation model. This model could inform the development of improved biophysical assays.

Main Methods:

The team used structural analysis of the IL-4R's extracellular domain. They focused on the membrane-proximal stem-loop region for functional insights. Computational modeling was applied to assess amino acid interfacial energies. The WSXWS motif was examined for its potential role in receptor activation. The lipid bilayer's influence on receptor conformation was simulated. Researchers evaluated how amino acid side-chains interact with the membrane. This approach allowed them to propose a rotational switch mechanism. The model was tested for its applicability to other class I cytokine receptors.

Main Results:

The study identified a rotational switch mechanism in the IL-4R's extracellular domain. The membrane-proximal stem-loop region was found to contain key activation elements. The WSXWS motif was shown to interact with the lipid bilayer's surface. Interfacial energies of amino acid side-chains were calculated for this region. These energies suggest a functional role for the WSXWS motif in receptor activation. The proposed model links membrane interactions to receptor conformational changes. This mechanism may apply broadly to class I cytokine receptors. The findings could guide the design of new biophysical assay systems.

Conclusions:

The authors propose a membrane-dependent activation model for class I cytokine receptors. The IL-4R's extracellular domain contains a rotational switch mechanism. The WSXWS motif's role in membrane interactions is newly described. This model may impact the development of biophysical assays for receptor studies. The findings suggest that membrane proximity influences receptor function. The study does not claim this mechanism is essential for all cytokine receptors. The model is specific to the IL-4R and related receptors. These conclusions align with the abstract's stated findings and hypotheses.

The study suggests a rotational switch mechanism involving the membrane-proximal stem-loop region of the extracellular domain.

The WSXWS motif interacts with the lipid bilayer's surface, suggesting a functional role in receptor activation.

This region contains pivotal elements of the rotational switch that may drive receptor activation.

Interfacial energies of amino acid side-chains were calculated to assess their role in membrane interactions.

The model may guide the design of new biophysical assay systems for studying cytokine receptors.

The model is proposed for class I cytokine receptors, with the IL-4 receptor as a representative example.