A leucine-rich repeat assembly approach for homology modeling of the human TLR5-10 and mouse TLR11-13 ectodomains

Abstract

So far, 13 groups of mammalian Toll-like receptors (TLRs) have been identified. Most TLRs have been shown to recognize pathogen-associated molecular patterns from a wide range of invading agents and initiate both innate and adaptive immune responses. The TLR ectodomains are composed of varying numbers and types of leucine-rich repeats (LRRs). As the crystal structures are currently missing for most TLR ligand-binding ectodomains, homology modeling enables first predictions of their three-dimensional structures on the basis of the determined crystal structures of TLR ectodomains. However, the quality of the predicted models that are generated from full-length templates can be limited due to low sequence identity between the target and templates. To obtain better templates for modeling, we have developed an LRR template assembly approach. Individual LRR templates that are locally optimal for the target sequence are assembled into multiple templates. This method was validated through the comparison of a predicted model with the crystal structure of mouse TLR3. With this method, we also constructed ectodomain models of human TLR5, TLR6, TLR7, TLR8, TLR9, and TLR10 and mouse TLR11, TLR12, and TLR13 that can be used as first passes for a computational simulation of ligand docking or to design mutation experiments. This template assembly approach can be extended to other repetitive proteins.

Recognition of CpG oligodeoxynucleotides by human Toll-like receptor 9 and subsequent cytokine induction

“…The Toll-like receptors (TLRs) are a class of pattern recognition receptors that recognize pathogen-associated molecular patterns (PAMPs), as well as play a critical role in the innate immune response to invading pathogens [1][2][3][4]. TLR9 is activated by DNA from invasive bacteria and by synthetic oligodeoxynucleotides (ODNs) containing unmethylated cytosine-phosphate-guanosine (CpG) motifs [5].…”

Micoses superficiais e os elementos da resposta imune

“…Thus, it is believed that human LC express functional TLRs, which are more active to stimulation with TLR2, 3, 7 and 8 ligands. 38 In vitro studies with other fungi or yeast, such as C. albicans, have shown that TLR2 recognizes the glycopeptide phospholipmannan on the surface of the cell wall of the micro-organism and TLR4 recognizes the polysaccharide mannan, also on the fungal cell wall. 43,44 That is, the expression of TLR2 and TLR4 in keratinocytes is important for the host defense against C. albicans.…”

“…39 Several studies have proved that these receptors are functional and participate in immune responses. 38,39 In vitro studies found that the supernatant from keratinocytes stimulated via TLR3 may stimulate immature DC derived from monocytes toward cell differentiation and, consequently, production of TNFα and type I IFNγ (type I interferon gamma), developing Th1 cell responses from wild-type T cells. 40 This indicates that keratinocytes can direct Th1-type adaptive immune responses.…”

“…These data demonstrate, in human keratinocytes, that functional TLRs may be important in the induction of different defense responses against various pathogens invading the skin. 38 There are several studies on the expression and function of TLRs in human LC. 38.39 Comparative studies showed that LC-type DC express the messenger RNA (mRNA) of TLRs 1 to 10 in a way similar to monocyte-derived DC.…”

“…37 Although TLRs belong to the innate immune system, they present specificity of response and participate in controlling the activation of the acquired immune response. 37 Currently, at least 13 different TLR(s) are known, 38 which recognize a wide variety of exogenous and endogenous antigens. The nature of the offending antigen and the TLR to which it binds will determine a specific repertoire of cytokines that is produced by antigen-presenting cells and polarize the acquired immune responses into Th1 or Th2 patterns (type 2 T-helper lymphocytes).…”