The myristoylation of TRIF-related adaptor molecule is essential for Toll-like receptor 4 signal transduction
Department of Medicine, Division of Infectious Diseases and Immunology
Medical Subject Headings
Adaptor Proteins, Vesicular Transport; Amino Acid Sequence; Animals; Bone Marrow Cells; Cell Membrane; Cells, Cultured; Humans; Lipopolysaccharides; Macrophages; Mice; Mice, Mutant Strains; Molecular Sequence Data; Mutation; Myristic Acid; Signal Transduction; Toll-Like Receptor 4
Immunology and Infectious Disease | Life Sciences | Medicine and Health Sciences
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.
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Citation: Proc Natl Acad Sci U S A. 2006 Apr 18;103(16):6299-304. Epub 2006 Apr 7. Link to article on publisher's site