Related Experiment Video

Updated: Jun 24, 2026

Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling
09:51

Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling

Published on: July 26, 2017

TLR4/MyD88/PI3K interactions regulate TLR4 signaling

Michelle H W Laird1, Sang Hoon Rhee, Darren J Perkins

  • 1University of Maryland, Baltimore, 660 W. Redwood Street, Room 324, Baltimore, MD 21201, USA.

Journal of Leukocyte Biology
|March 18, 2009
PubMed

Insights

Toll-like receptor 4 (TLR4) signaling, crucial for immune responses, involves MyD88 and PI3K. Sustained interaction negatively regulates signaling, suggesting a feedback mechanism.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cell Signaling

Background:

  • Toll-like receptors (TLRs) initiate immune responses by detecting microbial and endogenous danger signals.
  • MyD88 is a key adapter protein mediating signal transduction for most TLRs, leading to NF-kappaB and MAPK activation.
  • TLR4 signaling specifically activates PI3K, regulating cell growth and apoptosis, and LPS stimulates Akt phosphorylation.

Purpose of the Study:

  • To investigate the role of the MyD88-PI3K interaction in TLR4-mediated signaling.
  • To determine the functional significance of a YXXM motif within the MyD88 TIR domain for PI3K binding.
  • To elucidate the impact of sustained PI3K activity on TLR4 signaling regulation.

Main Methods:

  • Co-immunoprecipitation analyses were used to assess binding between MyD88 variants, PI3K p85, and TLR4.
  • MyD88 variants with mutations in the YXXM motif, TIR domain, or death domain were expressed and tested.
  • LPS-induced Akt phosphorylation was measured in wild-type and MyD88(-/-) macrophages.

Main Results:

  • LPS-induced Akt phosphorylation was TLR4-dependent and blunted in MyD88(-/-) macrophages.
  • A YXXM to YXXA mutant MyD88 showed increased binding to p85, TLR4, and WT MyD88.
  • This YXXA mutant exhibited significantly reduced signaling activity compared to WT MyD88.

Conclusions:

  • Sustained interaction of MyD88/PI3K with the TLR4 signaling platform negatively regulates TLR4 signaling.
  • A hypothetical model suggests that sustained PI3K activity limits substrate availability, downregulating signaling.
  • This finding provides insights into the negative feedback mechanisms governing TLR4 immune responses.

More Related Videos

Using RNA-interference to Investigate the Innate Immune Response in Mouse Macrophages12:47

Using RNA-interference to Investigate the Innate Immune Response in Mouse Macrophages

Published on: November 3, 2014

Fluorescence Assays for the Study of Mycobacterium tuberculosis Interaction with the Immune Receptor SLAMF107:42

Fluorescence Assays for the Study of Mycobacterium tuberculosis Interaction with the Immune Receptor SLAMF1

Published on: February 28, 2025

Related Concept Videos

The JAK-STAT Signaling Pathway01:20

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...
PI3K/mTOR/AKT Signaling Pathway01:22

PI3K/mTOR/AKT Signaling Pathway

The mammalian target of rapamycin  (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1  (mTORC1) and mTOR complex 2  (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast,  mTORC2 consists of a rapamycin-insensitive companion...
TGF - β Signaling Pathway01:16

TGF - β Signaling Pathway

The TGF-β signaling pathway regulates cell growth, differentiation, adhesion, motility, and development. TGF-β ligands that induce TGF-β signaling are synthesized in their latent form. Several proteases or cell surface receptors such as integrins act upon the latent form, releasing the active ligand. There are three types of mammalian TGF-βs: (TGF-β1, TGF-β2, and TGF-β3) that bind as homodimers or heterodimers to TGF-β receptors. The TGF-β receptors are of three kinds RI, RII, and RIII. The RI...
Interactions Between Signaling Pathways01:19

Interactions Between Signaling Pathways

Signaling cascades usually lack linearity. Multiple pathways interact and regulate one another, allowing cells to integrate and respond to diverse environmental stimuli.
Convergence and divergence, and cross-talk between signaling pathways
Two distinct signaling pathways can converge on a single functional unit, which may either be a single protein or a complex of proteins. The response is either functionally distinct or synergistic between the two pathways but different from the response...
Formation of Lipopolysaccharides01:19

Formation of Lipopolysaccharides

Lipopolysaccharides (LPS) are crucial components of the outer membrane of Gram-negative bacteria, serving both structural and functional roles. It contributes to membrane stability and protects bacteria from host immune responses. LPS is composed of three major regions—lipid A, a core oligosaccharide, and an O antigen. The biosynthesis and assembly of LPS involve a highly coordinated set of enzymatic reactions and transport mechanisms. Additionally, LPS is recognized as an endotoxin, triggering...
Regulation of the Unfolded Protein Response01:31

Regulation of the Unfolded Protein Response

Inositol-requiring kinase one or IRE1 is the most conserved eukaryotic unfolded protein response (UPR) receptor. It is a type I transmembrane protein kinase receptor with a distinctive site-specific RNase activity. As the binding mechanics of the misfolded proteins with the N-terminal domain of IRE-1 are unclear, three binding models — direct, indirect, and allosteric -- are proposed for receptor activation. Nevertheless, it is known that once a misfolded protein associates with IRE1, it...