Dynamics on human Toll‐like receptor 4 complexation to MD‐2: The coreceptor stabilizing function

Abstract

The interaction between human Toll-like receptor 4 (hTLR4) and its coreceptor, myeloid differentiation factor 2 (MD-2), is important in Gram-negative bacteria lipopolysaccharide (LPS) recognition. In this process, MD-2 recognizes LPS and promotes the dimerization of the complex hTLR4-MD-2-LPS, triggering an intracellular immune signaling. In this study, we employed distinct computational methods to explore the dynamical properties of the hTLR4-MD-2 complex and investigated the implications of the coreceptor complexation to the structural biology of hTLR4. We characterized both global and local dynamics of free and MD-2 complexed hTLR4, in both (hTLR4-MD-2)1 and (hTLR4-MD-2)2 states. Both molecular dynamics and normal mode analysis reveled a stabilization of the terminal regions of hTLR4 upon complexation to MD-2. We are able to identify conserved important residues involved on the hTLR4-MD-2 interaction dynamics and disclose C-terminal motions that may be associated to the signaling process upon oligomerization.

Molecular Basis of Artemisinin Derivatives Inhibition of Myeloid Differentiation Protein 2 by Combined in Silico and Experimental Study

“…This observation may suggest that the binding of artemisinin and its derivatives to MD-2 reduces the conformational changes of the 7– 8 loop thereby inhibiting TLR4-MD-2 dimerization and preventing immune response. Although the loop region 3– 4 does not interact directly with TLR4, decreased fluctuations were observed upon ligand binding, suggesting that this region also had an influence on the dimerizaiton activity of TLR4-MD-2, which is consistent with previous TLR4-MD-2 simulations [ 37 , 38 ]. In contrast, the loop region bridging 6 and 7 (residue C95–T112) showed a increased fluctuations upon ligand binding, which is located at the primary contact interface between TLR4 and MD-2.…”

Insights into the dynamic nature of the dsRNA-bound TLR3 complex

“…Unlike other TLRs, endosomal TLRs may exist as pre-formed dimers, as suggested for human TLR9 25 , and TLR3 ECD dimerization is required for effective ligand binding 24 . In our simulations, apo_dTLR3 WT (dsRNA-unbound TLR3-ECD dimer) showed large RMSD fluctuations compared to dsRNA bound TLR3 complexes, which is similar to the previous results obtained for apo TLR4 dimer 27 . However, the MD-2 binds to the concave region of TLR4 and acts as co-receptor whereas dsRNA binds to TLR3 at the N-terminal (LRR-NT and LRR1-3) and C-terminal (LRR 19–21) site of individual TLR3 monomers in the lateral convex surface.…”

“…We investigated the dynamic behavior of all five TLR3 complexes using molecular dynamic (MD) simulations to elucidate the initial mechanism of dsRNA binding to TLR3 at the extracellular surface. Computational approaches and MD simulations are often used to determine protein structure-function relationships via ligand- and mutation-induced conformational changes 26,27 . Subsequently, we employed a principal component analysis (PCA) and residue network centrality analysis 28 to investigate the global motions and the distribution of crucial residues for signal transmission within the TLR3 complexes, respectively.…”

Computational Approaches to Toll-Like Receptor 4 Modulation

“…The TLR4 ectodomain and its dimerization mechanism have been the main subject of several computational studies. MD simulations have been reported by de Aguiar et al of TLR4 alone, MD-2 alone, TLR4/MD-2 complex and TLR4/MD-2/TLR4*/MD-2* complex [21]. The simulations of the TLR4 ectodomain revealed pronounced conformation and structure alterations in the N- and C-terminal domains, showing higher RMSD values compared to the full protein RMSD values.…”