Mycobacterium tuberculosis Lipoprotein and Lipoglycan Binding to Toll-Like Receptor 2 Correlates with Agonist Activity and Functional Outcomes

Abstract

causes persistent infection due to its ability to evade host immune responses. induces Toll-like receptor 2 (TLR2) signaling, which influences immune responses to TLR2 agonists expressed by include lipoproteins (e.g., LprG), the glycolipid phosphatidylinositol mannoside 6 (PIM6), and the lipoglycan lipomannan (LM). Another lipoglycan, mannose-capped lipoarabinomannan (ManLAM), lacks TLR2 agonist activity. In contrast, PILAM, from , does have TLR2 agonist activity. Our understanding of how lipoproteins and lipoglycans interact with TLR2 is limited, and binding of these molecules to TLR2 has not been measured directly. Here, we directly measured lipoprotein and lipoglycan binding to TLR2 and its partner receptor, TLR1. LprG, LAM, and LM were all found to bind to TLR2 in the absence of TLR1, but not to TLR1 in the absence of TLR2. Trimolecular interactions were revealed by binding of TLR2-LprG or TLR2-PIM6 complexes to TLR1, whereas binding of TLR2 to TLR1 was not detected in the absence of the lipoprotein or glycolipid. ManLAM exhibited low affinity for TLR2 in comparison to PILAM, LM, and LprG, which correlated with reduced ability of ManLAM to induce TLR2-mediated extracellular-signal-regulated kinase (ERK) activation and tumor necrosis factor alpha (TNF-α) secretion in macrophages. We provide the first direct affinity measurement and kinetic analysis of lipoprotein and lipoglycan binding to TLR2. Our results demonstrate that binding affinity correlates with the functional ability of agonists to induce TLR2 signaling.

Increased drug permeability of a stiffened mycobacterial outer membrane in cells lacking MFS transporter Rv1410 and lipoprotein LprG

“…Surface plasmon resonance (SPR) studies using purified LprG and triacylated lipids including LAM further confirmed this molecular interaction and revealed a secondary sugar‐binding site outside of the hydrophobic pocket, resulting in a particularly high affinity of LprG for LAMs (Shukla et al , ). Very recent studies in addition revealed molecular interactions of purified LprG with TLR2 (Shukla et al , ). Virulence of M. tuberculosis Δ lprG in BALB/c mice was clearly attenuated and the mutant exhibits impaired macrophage entry and fails to inhibit phagosome–lysosome fusion (Bigi et al , ).…”

Antibiotics and resistance: the two-sided coin of the mycobacterial cell wall

“…LAM and LM both play an important role in the modulation of the host’s immune defences ( Schlesinger et al, 1994 , Shukla et al, 2018 ). A variety of LAM caps exist, each affecting the immune response in different ways.…”

Host Immune Response and Novel Diagnostic Approach to NTM Infections

“…TLRs 2, 4, and 9 reportedly recognize mycobacteria [14][15][16][17]. TLR2 recognizes lipoproteins, peptidoglycan, and glycolipids (e.g., LAM, LM, and PIMs) [18,19]. With respect to NTM infection, TLR2 (not TLR4) has been reported to recognize Mycobacterium avium in vitro [20].…”