The myristoylation of TRIF-related adaptor molecule is essential for Toll-like receptor 4 signal transduction.

Division of Infectious Disease and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 05/2006; 103(16):6299-304. DOI: 10.1073/pnas.0510041103
Source: PubMed

ABSTRACT TRIF-related adaptor molecule (TRAM) is the fourth Toll/IL-1 resistance domain-containing adaptor to be described that participates in Toll-like receptor (TLR) signaling. TRAM functions exclusively in the TLR4 pathway. Here we show by confocal microscopy that TRAM is localized in the plasma membrane and the Golgi apparatus, where it colocalizes with TLR4. Membrane localization of TRAM is the result of myristoylation because mutation of a predicted myristoylation site in TRAM (TRAM-G2A) brought about dissociation of TRAM from the membrane and its relocation to the cytosol. Further, TRAM, but not TRAM-G2A, was radiolabeled with [3H]myristate in vivo. Unlike wild-type TRAM, overexpression of TRAM-G2A failed to elicit either IFN regulatory factor 3 or NF-kappaB signaling. Moreover, TRAM-G2A was unable to reconstitute LPS responses in bone marrow-derived macrophages from TRAM-deficient mice. These observations provide clear evidence that the myristoylation of TRAM targets it to the plasma membrane, where it is essential for LPS responses through the TLR4 signal transduction pathway, and suggest a hitherto unappreciated manner in which LPS responses can be regulated.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Over the last twenty years, evidence has been provided that the plasma membrane is partitioned with microdomains, laterally mobile in the bilayer, providing the necessary microenvironment to specific membrane proteins for signalling pathways to be initiated. We discuss here the importance of such microdomains for Toll-like receptors (TLR) localization and function. First, lipid microdomains favour recruitment and clustering of the TLR machinery partners, i.e. receptors and co-receptors previously identified to be required for ligand recognition and signal transmission. Further, the presence of the so-called Cholesterol Recognition Amino-Acid Consensus (CRAC) sequences in the intracellular juxtamembrane domain of several Toll-like receptors suggests a direct role of cholesterol in the activation process. This article is part of a Special Issue entitled: Lipid-protein interactions. Copyright © 2015. Published by Elsevier B.V.
    Biochimica et Biophysica Acta 03/2015; DOI:10.1016/j.bbamem.2015.03.014 · 4.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The problem of recognizing and disposing of non-self-organisms, whether for nutrients or defense, predates the evolution of multicellularity. Accordingly, the function of the innate immune system is often intimately associated with fundamental aspects of cell biology. Here, we review our current understanding of the links between cell biology and pattern-recognition receptors of the innate immune system. We highlight the importance of receptor localization for the detection of microbes and for the initiation of antimicrobial signaling pathways. We discuss examples that illustrate how pattern-recognition receptors influence, and are influenced by, the general membrane trafficking machinery of mammalian cells. In the future, cell biological analysis likely will rival pure genetic analysis as a tool to uncover fundamental principles that govern host-microbe interactions.
    Cold Spring Harbor perspectives in biology 11/2014; DOI:10.1101/cshperspect.a016253 · 8.23 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Toll-like receptors (TLRs) are receptors involved in sensing invading microbes by host innate immunity. TLR2 recognizes bacterial lipoproteins/lipopeptides, while lipopolysaccharide (LPS) activates TLR4. TLR2 and TLR4 signal via the Toll/Interleukin-1 receptor (TIR) adaptors MyD88 and MAL, leading to NF-κB activation. TLR4 also utilizes the adaptors TRAM and TRIF, resulting in activation of interferon regulatory factor (IRF)3. Here we report a new role for TRAM and TRIF in TLR2 regulation and signaling. Interestingly, we observed that TLR2-mediated induction of the chemokine CCL5 was impaired in TRAM-/- or TRIF-/- macrophages. Inhibition of endocytosis reduced CCL5 release, and the data also suggested that TRAM and TLR2 co-localize in early endosomes, supporting the hypothesis that signaling may occur from an intracellular compartment. CCL5 release following lipoprotein challenge additionally involved the kinase TBK-1 and IRF3, as well as MyD88 and IRF1. Induction of interferon-β and CCL4 by lipoproteins were also partially impaired in TRIF-/- cells. Our results show a novel function of TRAM and TRIF in TLR2-mediated signal transduction, and the findings broaden our understanding of how TIR adaptor proteins may participate in signaling downstream from TLR2. Copyright © 2014, The American Society for Biochemistry and Molecular Biology.
    Journal of Biological Chemistry 12/2014; DOI:10.1074/jbc.M114.593426 · 4.60 Impact Factor

Full-text (2 Sources)

Available from
Jun 1, 2014