A phosphorylation site in the Toll-like receptor 5 TIR domain is required for inflammatory signalling in response to flagellin.
Flagellin, the major structural subunit of bacterial flagella, potently induces inflammatory responses in mammalian cells by activating Toll-like receptor (TLR) 5. Like other TLRs, TLR5 recruits signalling molecules to its intracellular TIR domain, leading to inflammatory responses. Phosphatidylinositol 3-kinase (PI3K) has been reported to play a role in early TLR signalling. We identified a putative binding site for PI3K at tyrosine 798 in the TLR5 TIR domain, at a site analogous to the PI3K recruitment domain in the interleukin-1 receptor. Mutation of this residue did not affect homodimerization, but prevented inflammatory responses to flagellin. While we did not detect direct interaction of PI3K with TLR5, we demonstrated by mass spectrometry that Y798 is phosphorylated in flagellin-treated HEK 293T cells. Together, these results suggest that phosphorylation of Y798 in TLR5 is required for signalling, but not for TLR5 dimerization.
Ivison
Sabine M
SM
Division of Infectious Diseases, University of British Columbia/Vancouver Coastal Health Research Institute, Canada.
Khan
Mohammed A S
MA
Graham
Nicholas R
NR
Bernales
Cecily Q
CQ
Kaleem
Arnawaz
A
Tirling
Chelsea O
CO
Cherkasov
Artem
A
Steiner
Theodore S
TS
D000595:Amino Acid Sequence; D002460:Cell Line; D018360:Crystallography, X-Ray; D019281:Dimerization; D005408:Flagellin / Q000494:pharmacology*; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D051198:Toll-Like Receptor 5 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism
D051198:Toll-Like Receptor 5; D005408:Flagellin; D014443:Tyrosine