Structural modelling and dynamics of full-length of TLR10 sheds light on possible modes of dimerization, ligand binding and mechanism of action

Toll like receptors (TLRs) play a pivotal role in innate and adaptive immunity. There are 10 TLRs in the human genome, of which TLR10 is the least characterized. Genetic polymorphism of TLR10 has been shown to be associated with multiple diseases including tuberculosis and rheumatoid arthritis. TLR10 consists of an extracellular domain (ECD), a single-pass transmembrane (TM) helix and intracellular TIR (Toll/Interleukin-1 receptor) domain. ECD is employed for ligand recognition and the intracellular domain interacts with other TIR domain-containing adapter proteins for signal transduction. Experimental structure of ECD or TM domain is not available for TLR10. In this study, we have modelled multiple forms of TLR10-ECD dimers, such as closed and open forms, starting from available structures of homologues. Subsequently, multiple full-length TLR10 homodimer models were generated by utilizing homology modelling and protein-protein docking. The dynamics of these models in membrane-aqueous environment revealed the global motion of ECD and TIR domain towards membrane bilayer. The TIR domain residues exhibited high root mean square fluctuation compared to ECD. The ‘closed form’ model was observed to be energetically more favorable than ‘open form’ model. The evaluation of persistent interchain interactions, along with their conservation score, unveiled critical residues for each model. Further, the binding of dsRNA to TLR10 was modelled by defined and blind docking approaches. Differential binding of dsRNA to the protomers of TLR10 was observed upon simulation that could provide clues on ligand disassociation. Dynamic network analysis revealed that the ‘open form’ model can be the functional form while ‘closed form’ model can be the apo form of TLR10.