TY - JOUR
T1 - Structural basis for TIR domain–mediated innate immune signaling by Toll-like receptor adaptors TRIF and TRAM
AU - Manik, Mohammad K.
AU - Pan, Mengqi
AU - Xiao, Le
AU - Gu, Weixi
AU - Kim, Hyoyoung
AU - Pospich, Sabrina
AU - Hedger, Andrew
AU - Vajjhala, Parimala R.
AU - Lee, Morris Y.L.
AU - Qian, Xiaoqi
AU - Landsberg, Michael J.
AU - Ve, Thomas
AU - Nanson, Jeffrey D.
AU - Raunser, Stefan
AU - Stacey, Katryn J.
AU - Wu, Hao
AU - Kobe, Bostjan
N1 - Publisher Copyright:
Copyright © 2025 the Author(s).
PY - 2025/1
Y1 - 2025/1
N2 - Innate immunity relies on Toll-like receptors (TLRs) to detect pathogen-associated molecular patterns. The TIR (Toll/interleukin-1 receptor) domain-containing TLR adaptors TRIF (TIR domain–containing adaptor-inducing interferon-β) and TRAM (TRIF-related adaptor molecule) are essential for MyD88-independent TLR signaling. However, the structural basis of TRIF and TRAM TIR domain–based signaling remains unclear. Here, we present cryo-EM structures of filaments formed by TRIF and TRAM TIR domains at resolutions of 3.3 Å and 5.6 Å, respectively. Both structures reveal two-stranded parallel helical arrangements. Functional studies underscore the importance of intrastrand interactions, mediated by the BB-loop, and interstrand interactions in TLR4-mediated signaling. We also report the crystal structure of the monomeric TRAM TIR domain bearing the BB loop mutation C117H, which reveals conformational differences consistent with its inactivity. Our findings suggest a unified signaling mechanism by the TIR domains of the four signaling TLR adaptors MyD88, MAL, TRIF, and TRAM and reveal potential therapeutic targets for immunity-related disorders.
AB - Innate immunity relies on Toll-like receptors (TLRs) to detect pathogen-associated molecular patterns. The TIR (Toll/interleukin-1 receptor) domain-containing TLR adaptors TRIF (TIR domain–containing adaptor-inducing interferon-β) and TRAM (TRIF-related adaptor molecule) are essential for MyD88-independent TLR signaling. However, the structural basis of TRIF and TRAM TIR domain–based signaling remains unclear. Here, we present cryo-EM structures of filaments formed by TRIF and TRAM TIR domains at resolutions of 3.3 Å and 5.6 Å, respectively. Both structures reveal two-stranded parallel helical arrangements. Functional studies underscore the importance of intrastrand interactions, mediated by the BB-loop, and interstrand interactions in TLR4-mediated signaling. We also report the crystal structure of the monomeric TRAM TIR domain bearing the BB loop mutation C117H, which reveals conformational differences consistent with its inactivity. Our findings suggest a unified signaling mechanism by the TIR domains of the four signaling TLR adaptors MyD88, MAL, TRIF, and TRAM and reveal potential therapeutic targets for immunity-related disorders.
KW - cryo-EM
KW - helical reconstruction
KW - MyD88-independent TLR signaling
KW - TIR domain
UR - https://www.scopus.com/pages/publications/85214929736
UR - https://www.scopus.com/pages/publications/85214929736#tab=citedBy
U2 - 10.1073/pnas.2418988122
DO - 10.1073/pnas.2418988122
M3 - Article
C2 - 39786929
AN - SCOPUS:85214929736
SN - 0027-8424
VL - 122
SP - 1
EP - 8
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 2
M1 - e2418988122
ER -