TLR2 dimer‐specific ligands selectively activate protein kinase C isoforms in Leishmania infection

Abstract

Of the thirteen Toll-like receptors (TLRs) in mice, TLR2 has a unique ability of forming heterodimers with TLR1 and TLR6. Such associations lead to selective cellular signalling and cellular responses such as cytokine expression. One of the signalling intermediates is protein kinase C (PKC); of which, eight isoforms are expressed in macrophages.Leishmania-a protozoan parasite that resides and replicates in macrophages-selectively modulates PKC-α, PKC-β, PKC-δ and PKC-ζ isoforms in macrophages. As TLR2 plays significant roles in Leishmania infection, we examined whether these PKC isoforms play selective roles in TLR2 signalling and TLR2-induced anti-leishmanial functions.We observed that the TLR2 ligands-Pam 3 CSK 4 (TLR1/2), PGN (TLR2/2) and FSL (TLR2/6)-differentially phosphorylated and translocated PKC-α, PKC-β, PKC-δ and PKC-ζ isoforms to cell membrane in uninfected and L. major-infected macrophages. The PKC isoform-specific inhibitors differentially altered IL-10 and IL-12 expression, Th1 and Th2 responses and anti-leishmanial effects in macrophages and in BALB/c mice.While PKC isoforms' inhibitors had insignificant effects on the Pam3CSK4-induced anti-leishmanial functions, PGN-induced pro-leishmanial effects were enhanced by PKC-(α + β) inhibitors, whereas PKC-(δ + ζ) inhibitors enhanced the anti-leishmanial effects of FSL. These results indicated that the ligand-induced TLR2 dimerization triggered differential dose-dependent and kinetic profiles of PKC isoform activation and that selective targeting of PKC isoforms using their respective inhibitors in combination significantly modulated TLR2-induced anti-leishmanial functions. To the best of our knowledge, this is the first demonstration of TLR2 dimer signalling through PKC isoforms and TLR2-induced PKC isoform-targeted anti-leishmanial therapy.

Leishmania surface molecule lipophosphoglycan‐TLR2 interaction moderates TPL2‐mediated TLR2 signalling for parasite survival

“…Cumulatively, the results connect TLR2 with TPL2 in the signalling chain. Visceral leishmaniasis has reported TLR2 mediated TNF‐α production as well as our lab has reported TLR2‐induced IL‐12 expression upon stimulation [36, 37]. In current work, with L. donovani infection the TLR2 blocking did not essentially affect either the pro‐inflammatory cytokine gene expression spike or the IL‐10 expression, rather did severely impair the TGF‐β expression.…”

Targeting of GSDMD sensitizes HCC to anti-PD-1 by activating cGAS pathway and downregulating PD-L1 expression

“… 33 We first found that K + concentration had no effect on the HCC cell viability ( online supplemental figure S4G ). We then used the TLR2 ligand Pam3CSK4 34 to stimulate the Huh7-GSDMD cells with or without KCl. The results found that KCl itself might not induce IFN-β after the stimulation of Pam3CSK4 ( online supplemental figure S4H ).…”

Anti-Leishmania major Properties of Nuphar lutea (Yellow Water Lily) Leaf Extracts and Purified 6,6′ Dihydroxythiobinupharidine (DTBN)

“…Cysteine proteases are omnipresent enzymes that are critically implicated in the pathogenesis of protozoic infections. Despite their significance, cysteine proteases as therapeutic targets have not yet been translated into clinical practice [36,37]. Both parasite and host proteinases are involved in the clinical manifestation of leishmaniasis [38].…”