Lamprey TLRs with Properties Distinct from Those of the Variable Lymphocyte Receptors

Abstract

Fish express mammalian-type (M-type) TLRs consisting of leucine-rich repeats (LRRs) and Toll-IL-1R (TIR) homology domain for immunity, whereas invertebrates in deuterostomes appear to have no orthologs of M-type TLRs. Lampetra japonica (lamprey) belongs to the lowest class of vertebrates with little information about its TLRs. We have identified two cDNA sequences of putative TLRs in the lamprey (laTLRs) that contain LRRs and TIR domains. The two laTLRs were 56% homologous to each other, and their TIRs were similar to those of members of the human TLR2 subfamily, most likely orthologs of fish TLR14. We named them laTLR14a and laTLR14b. We raised a rabbit polyclonal Ab against laTLR14b and identified a 85-kDa protein in a human HEK293 transfectant by immunoblotting using the Ab. FACS, histochemical, and confocal analyses showed that laTLR14b is expressed intracellularly in lamprey gill cells and that the overexpressed protein resides in the endoplasmic reticulum of human and fish (medaka) cell lines. Because natural agonists of TLR14 remained unidentified, we made a chimera construct of extracellular CD4 and the cytoplasmic domain of laTLR14. The chimera molecule of laTLR14b, when expressed in HEK293 cells, elicited activation of NF-κB and, consequently, weak activation of the IFN-β promoter. laTLR14b mRNA was observed in various organs and leukocytes. This lamprey species expressed a variable lymphocyte receptor structurally independent of laTLR14 in leukocytes. Thus, the jawless vertebrate lamprey possesses two LRR-based recognition systems, the variable lymphocyte receptor and TLR, and the M-type TLRs are conserved across humans, fish, and lampreys.

Combinational recognition of bacterial lipoproteins and peptidoglycan by chicken Toll-like receptor 2 subfamily

“…In contrast, fish and xenopus have unique TLR2 subfamilies of TLR1, TLR2 and TLR14 (2,8,16). Even the lamprey appears to have the TLR2 subfamily (17).…”

Cloning and expression of Toll-like receptors 1 and 2 from a teleost fish, the orange-spotted grouper Epinephelus coioides

“…In mammal, TLR2 is involved in the recognition of a wide range of PAMPs, such as lipopeptides from bacteria, and peptidoglycan and lipoteichoic acid from Gram-positive bacteria, through the interaction with other receptors, such as TLR1 and TLR6, and also CD36 and CD14 (Kawai and Akira, 2010). In teleost fish, TLR6 and TLR10 are not identified, and TLR4 is only found in pufferfish and zebrafish as well as in lamprey (Lampetra japonica) (Ishii et al, 2007). But unlike in mammal, TLR4 in zebrafish does not recognize LPS (Sepulcre et al, 2009); and recent research has shown that TLR2 in fish may be incorporated with PGRP (Chang and Nie, 2008), and can indeed bind lipoteichoic acid and peptidoglycan, as mammalian TLR2 (Ribeiro et al, 2010).…”

Arabidopsis thaliana Pattern Recognition Receptors for Bacterial Elongation Factor Tu and Flagellin Can Be Combined to Form Functional Chimeric Receptors

“…Anchoring to the plasma membrane might be important to keep the pre- EFR-FLS2 Chimeras-To study the elf binding properties and EFR functionality, we substituted parts of the receptor by corresponding parts of the closely related LRR receptor kinase FLS2. Chimeric constructions with domain swaps between different receptors have previously been used to investigate specificity of ligand interaction and signal output of Toll-like receptors in humans and animals (29,30). In plants, a much-noticed first example was reported for a chimera of the pattern recognition receptor XA21 from rice and the brassinolide receptor BRI1 from A. thaliana (31).…”