| Research Abstract |
M161Ag is a 43 kDa surface lipopiotein of Mycoplasma frrmentans, sewing as a potent cytokine inducerin monocytes/macrophages, maturing dendritic cells (DCs) and activating host complement on aikcted cells. It possesses a unique N-terminal lipo-arnino acid, N-acyl-S-diacylglyceryl cysteine with a free N-terminus. MALP-2 recently identified as a ligand for Toll-like receptor 2 (TLR2) is derived fiom M16IAg. Here, we identified structural motifs sustaining the functions of M161Ag using wild-type and various forms of recombinant M16IAg (rMl6IAg) with (sp+) or without signal peptides (sp-). Since the sp+ rM161Ag formed dimer via 25Cys, we obtained a monomeric form by mutagenesis (sp+ C25S). Only wild-type accelerates maturation of DCs by the CD83/86 criteria, suggesting the importance of the N-terminal fatty acids for this function. Wild-type and the sp+ form of monomer allowed to secrete TNFα and IL-12 p4 monocytes and DCs. Monomeric form with N-terminal hydrophobic portion, either lipid or sp, is required fbr expression of this function, though high doses were needed in the sp+ form. Wild-type and both monomeric and dimeric sp+ forms possess the ability to activate complement via the alternative pathway. Again, the hydiophobic portion is associated with this function. These results, together with the finding that TLR2-deflcient macrophages did not pmduce any detectable levels of TNFα in response to MALP-2. infer that the lipid moiety of MI61Ag participates in TLR2-mediated cell activation. The three functions of MI61Ag can be independent, being sustained by either lipid, sp, or monomeric form.
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