Requirement of Mitogen-Activated Protein Kinases and IκB Phosphorylation for Induction of Proinflammatory Cytokines Synthesis by Macrophages Indicates Functional Similarity of Receptors Triggered by Glycosylphosphatidylinositol Anchors from Parasitic Protozoa and Bacterial Lipopolysaccharide

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Abstract
In the present study, we evaluated the ability of GPI-anchored mucin-like glycoproteins purified from Trypanosoma cruzi trypomastigotes (tGPI-mucin) to trigger phosphorylation of different mitogen-activated protein kinases (MAPKs) and related transcription factors in inflammatory macrophages. Kinetic experiments show that the peak of extracellular signal-related kinase (ERK)-1/ERK-2, stress-activated protein kinase (SAPK) kinase-1/mitogen-activated protein kinase (MAPK) kinase-4, and p38/SAPK-2, phosphorylation occurs between 15 and 30 min after macrophage stimulation with tGPI-mucin or GPI anchors highly purified from tGPI-mucins (tGPI). The use of the specific inhibitors of ERK-1/ERK-2 (PD 98059) and p38/SAPK-2 (SB 203580) phosphorylation also indicates the role of MAPKs, with possible involvement of cAMP response element binding protein, in triggering TNF-α and IL-12 synthesis by IFN-γ-primed-macrophages exposed to tGPI or tGPI-mucin. In addition, tGPI-mucin and tGPI were able to induce phosphorylation of IκB, and the use of SN50 peptide, an inhibitor of NF-κB translocation, resulted in 70% of TNF-α synthesis by macrophages exposed to tGPI-mucin. Finally, the similarity of patterns of MAPK and IκB phosphorylation, the concentration of drugs required to inhibit cytokine synthesis, as well as cross-tolerization exhibited by macrophages exposed to tGPI, tGPI-mucin, or bacterial LPS, suggest that receptors with the same functional properties are triggered by these different microbial glycoconjugates.

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