Divergent Roles of Amino Acid Residues Inside and Outside the BB Loop Affect Human Toll-Like Receptor (TLR)2/2, TLR2/1 and TLR2/6 Responsiveness

Qiu, Yuan; Ding, Yan; Zou, Lingyun; Tan, Zhangping; Liu, Taiping; Fu, Xiaolan; Xu, Wenyue

doi:10.1371/journal.pone.0061508

Cited by 14 publications

(26 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our results show that both TLR2/1 and TLR2/6 yielded an inhibitory effect on SERT by triggering the same mechanism. These results may suggest a redundant effect of TLR2 in intestinal epithelial cells; this feature of TLR2 has also been found in other cell types [48], although recent results have concluded that TLR2/1 and TLR2/6 could exhibit specific signaling transduction [49]. In relation to the ability shown by TLR2 to inhibit SERT activity and expression by different pathways depending on the period of treatment, it might be considered an advantageous way of specialization to modulate 5-HT in different situations.…”

Section: Discussionmentioning

confidence: 90%

Intestinal Serotonin Transporter Inhibition by Toll-Like Receptor 2 Activation. A Feedback Modulation

et al. 2016

View full text Add to dashboard Cite

TLR2 is a microbiota recognition receptor that has been described to contribute to intestinal homeostasis and to ameliorate inflammatory intestinal injury. In this context, serotonin (5-HT) has shown to be an essential intestinal physiological neuromodulator that is also involved in intestinal inflammatory diseases. Since the interaction between TLR2 activation and the intestinal serotoninergic system remains non-investigated, our main aim was to analyze the effect of TLR2 on intestinal serotonin transporter (SERT) activity and expression and the intracellular pathways involved. Caco-2/TC7 cells were used to analyze SERT and TLR2 molecular expression and SERT activity by measuring 5-HT uptake. The results showed that apical TLR2 activation inhibits SERT activity in Caco-2/TC7 cells mainly by reducing SERT protein level either in the plasma membrane, after short-term TLR2 activation or in both the plasma membrane and cell lysate, after long-term activation. cAMP/PKA pathway appears to mediate short-term inhibitory effect of TLR2 on SERT; however, p38 MAPK pathway has been shown to be involved in both short- and long-term TLR2 effect. Reciprocally, 5-HT long-term treatment yielded TLR2 down regulation in Caco-2/TC7 cells. Finally, results from in vivo showed an augmented intestinal SERT expression in mice Tlr2-/-, thus confirming our inhibitory effect of TLR2 on intestinal SERT in vitro. The present work infers that TLR2 may act in intestinal pathophysiology, not only by its inherent innate immune role, but also by regulating the intestinal serotoninergic system.

show abstract

Section: Discussionmentioning

confidence: 90%

Intestinal Serotonin Transporter Inhibition by Toll-Like Receptor 2 Activation. A Feedback Modulation

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Here, we report a novel method of TIR domain alignment of MyD88-dependent pathwaymediated TLRs with MyD88-independent pathway-mediated TLR3 to identify essential residues in the TLR4 signaling pathway. This approach is simple and informative and was successful in the identification of three critical amino acids in TLR2 signaling [18]. Although both L696 and P714 were demonstrated in a previous study to be essential for TLR4 signaling using systemically alanine replacement [17], our approach also revealed an additional critical residue: N721.…”

Section: Discussionmentioning

confidence: 81%

Three conserved MyD88-recruiting TLR residues exert different effects on the human TLR4 signaling pathway

et al. 2015

Self Cite

View full text Add to dashboard Cite

Stimulation of Toll-like receptor (TLR) 4 leads to the activation of both MyD88-dependent and MyD88-independent pathways through the recruitment of adaptors TIRAP/MyD88 and TRIF/TRAM, respectively. However, the molecular basis of the TLR4 Toll/interleukin-1 receptor (TIR) domain in recruiting these downstream adaptors is still not entirely clear. Here, we identify three amino acid residues (714P in the BB loop, 696L in the αA helix and 721N in the αB sheet) conserved in all MyD88-recruited TLRs, but not the TLR3 TIR domain, as being critical for TLR4 responsiveness to LPS. These results were based on the substitution of each residue with a residue of the opposite type (hydrophilic/hydrophobic). However, the responsiveness of the TLR4 mutants to LPS was only partially decreased when each residue was replaced with a residue having the same hydrophilicity/hydrophobicity. This result is likely associated with an alteration in the BB-loop conformation of each TLR4 mutant and its ability to recruit the downstream adaptor TRAM. Thus, we identified three amino acids essential for TLR4 signaling, and their replacement with a residue of the same or opposite hydrophilicity/hydrophobicity greatly affected TLR4 signaling. This study furthers our understanding of the molecular mechanism by which the TLR4 TIR domain modulates TLR4 signaling and also provides new insight for the design of antisepsis therapy.

show abstract

“…However, in the P681H mutant, additional interactions are formed with residues from the αC helix (Supporting Information, Figure S11F). Residues 713C, 748R, 749F,752L, and 753R were identified to be crucial for TLR1‐TLR2 signaling using alanine‐scanning mutagenesis . Among these, 752L, 749F, and 712W are few residues mediating the network of interactions in Community 2.…”

Section: Resultsmentioning

confidence: 99%

“…Phosphorylation of Tyr 761 in the TIR domain of TLR2 is essential for its proper functioning . TLR2‐mediated signaling has been well‐studied and ample experimental information is known, including the effect of various mutations in its TIR domain on its function …”

Section: Introductionmentioning

confidence: 99%

Probing subtle conformational changes induced by phosphorylation and point mutations in the TIR domains of TLR2 and TLR3

Mahita

Sowdhamini

2018

Proteins

View full text Add to dashboard Cite

Extensive research performed on Toll-like receptor (TLR) signaling has identified residues in the Toll/interleukin-1 receptor (TIR) domains that are essential for its proper functioning. Among these residues, those in BB loop are particularly significant as single amino acid mutations in this region can cause drastic changes in downstream signaling. However, while the effect of these mutations on the function is well studied (like the P681H mutation in TLR2, the A795P mutation in TLR3, and the P714H mutation in TLR4), their influence on the dynamics and inter-residue networks is not well understood. The effects of local perturbations induced by these mutations could propagate throughout the TIR domain, influencing interactions with other TIR domain-containing proteins. The identification of these subtle changes in inter-residue interactions can provide new insights and structural rationale for how single-point mutations cause drastic changes in TIR-TIR interactions. We employed molecular dynamics simulations and protein structure network (PSN) analyses to investigate the structural transitions with special emphasis on TLR2 and TLR3. Our results reveal that phosphorylation of the Tyr 759 residue in the TIR domain of TLR3 introduces rigidity to its BB loop. Subtle differences in the intra BB loop hydrogen bonding network between TLR3 and TLR2 are also observed. The PSN analyses indicate that the TIR domain is highly connected and pinpoints key differences in the inter-residue interactions between the wild-type and mutant TIR domains, suggesting that TIR domain structure is prone to allosteric effects, consistent with the current view of the influence of allostery on TLR signaling.

show abstract

Divergent Roles of Amino Acid Residues Inside and Outside the BB Loop Affect Human Toll-Like Receptor (TLR)2/2, TLR2/1 and TLR2/6 Responsiveness

Cited by 14 publications

References 31 publications

Intestinal Serotonin Transporter Inhibition by Toll-Like Receptor 2 Activation. A Feedback Modulation

Intestinal Serotonin Transporter Inhibition by Toll-Like Receptor 2 Activation. A Feedback Modulation

Three conserved MyD88-recruiting TLR residues exert different effects on the human TLR4 signaling pathway

Probing subtle conformational changes induced by phosphorylation and point mutations in the TIR domains of TLR2 and TLR3

Contact Info

Product

Resources

About