A family of human receptors structurally related to Drosophila Toll

Fernando L. Rock, Gary Hardiman, Jackie C. Timans, Robert A. Kastelein, J. Fernando Bazan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1404 Citations (Scopus)


The discovery of sequence homology between the cytoplasmic domains of Drosophila Toll and human interleukin 1 receptors has sown the conviction that both molecules trigger related signaling pathways tied to the nuclear translocation of Rel-type transcription factors. This conserved signaling scheme governs an evolutionarily ancient immune response in both insects and vertebrates. We report the molecular cloning of a class of putative human receptors with a protein architecture that is similar to Drosophila Toll in both intra- and extracellular segments. Five human Toll-like receptors-named TLRs 1-5-are probably the direct homologs of the fly molecule and, as such, could constitute an important and unrecognized component of innate immunity in humans. Intriguingly, the evolutionary retention of TLRs in vertebrates may indicate another role-akin to Toll in the dorsoventralization of the Drosophila embryo-as regulators of early morphogenetic patterning. Multiple tissue mRNA blots indicate markedly different patterns of expression for the human TLRs. By using fluorescence in situ hybridization and sequence-tagged site database analyses, we also show that the cognate Tlr genes reside on chromosomes 4 (TLRs 1, 2, and 3), 9 (TLR4), and 1 (TLR5). Structure prediction of the aligned Toll-homology domains from varied insect and human TLRs, vertebrate interleukin 1 receptors and MyD88 factors, and plant disease-resistance proteins recognizes a parallel β/α fold with an acidic active site; a similar structure notably recurs in a class of response regulators broadly involved in transducing sensory information in bacteria.

Original languageEnglish
Pages (from-to)588-593
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number2
Publication statusPublished - 20 Jan 1998
Externally publishedYes

ASJC Scopus subject areas

  • General


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