Identification of Toll-like receptor signaling inhibitors based on selective activation of hierarchically acting signaling proteins

Sirish K. Ippagunta, Julie A. Pollock, Naina Sharma, Wenwei Lin, Taosheng Chen, Kazuki Tawaratsumida, Anthony A. High, Jaeki Min, Yizhe Chen, R. Kiplin Guy, Vanessa Redecke, John A. Katzenellenbogen, Hans Häcker

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Toll-like receptors (TLRs) recognize various pathogen- and host tissue-derived molecules and initiate inflammatory immune responses. Exaggerated or prolonged TLR activation, however, can lead to etiologically diverse diseases, such as bacterial sepsis, metabolic and autoimmune diseases, or stroke. Despite the apparent medical need, no small-molecule drugs against TLR pathways are clinically available. This may be because of the complex signaling mechanisms of TLRs, which are governed by a series of protein-protein interactions initiated by Toll/interleukin-1 receptor homology domains (TIR) found in TLRs and the cytoplasmic adaptor proteins TIRAP and MyD88. Oligomerization of TLRs with MyD88 or TIRAP leads to the recruitment of members of the IRAK family of kinases and the E3 ubiquitin ligase TRAF6. We developed a phenotypic drug screening system based on the inducible homodimerization of either TIRAP, MyD88, or TRAF6, that ranked hits according to their hierarchy of action. From a bioactive compound library, we identified methyl-piperidino-pyrazole (MPP) as a TLRspecific inhibitor. Structure-activity relationship analysis, quantitative proteomics, protein-protein interaction assays, and cellular thermal shift assays suggested that MPP targets the TIR domain of MyD88. Chemical evolution of the original MPP scaffold generated compounds with selectivity for distinct TLRs that interfered with specific TIR interactions. Administration of an MPP analog to mice protected them from TLR4-dependent inflammation. These results validate this phenotypic screening approach and suggest that the MPP scaffold could serve as a starting point for the development of anti-inflammatory drugs.

Original languageEnglish
Article numbereaaq1077
JournalScience Signaling
Issue number543
StatePublished - Aug 14 2018

Bibliographical note

Funding Information:
We acknowledge the staff of the Animal Resource Center at the St. Jude Children's Research Hospital and the Centers of the Department of Chemical Biology and Therapeutics. We also thank L. Tang and Y. Sun (St. Jude Children's Research Hospital) for support with statistical analyses, and R. Wu for technical contributions. This work was supported by the NIH (PHS 5R01 DK015556 to J.A.K. and T32ES007326 to J.A.P.), the St. Jude Children's Infection Defense Center, and the American Lebanese Syrian Associated Charities.

Publisher Copyright:
© 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science.

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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