The myristoylation of TRIF-related adaptor molecule is essential for Toll-like receptor 4 signal transduction.
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.
Rowe
Daniel C
DC
Division of Infectious Disease and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.
McGettrick
Anne F
AF
Latz
Eicke
E
Monks
Brian G
BG
Gay
Nicholas J
NJ
Yamamoto
Masahiro
M
Akira
Shizuo
S
O'Neill
Luke A
LA
Fitzgerald
Katherine A
KA
Golenbock
Douglas T
DT
D033942:Adaptor Proteins, Vesicular Transport / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001854:Bone Marrow Cells / Q000187:drug effects / Q000276:immunology; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002478:Cells, Cultured; D006801:Humans; D008070:Lipopolysaccharides / Q000276:immunology / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D008817:Mice, Mutant Strains; D008969:Molecular Sequence Data; D009154:Mutation; D019814:Myristic Acid / Q000378:metabolism; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000032:analysis / Q000378:metabolism*
D033942:Adaptor Proteins, Vesicular Transport; D008070:Lipopolysaccharides; C470409:TICAM1 protein, human; D051197:Toll-Like Receptor 4; D019814:Myristic Acid