Macrophage stimulation with Murabutide, an HIV-suppressive muramyl peptide derivative, selectively activates extracellular signal-regulated kinases 1 and 2, C/EBPbeta and STAT1: role of CD14 and Toll-like receptors 2 and 4.
The smallest unit of bacterial peptidoglycans known to be endowed with biological activities is muramyl dipeptide (MDP). A clinically acceptable synthetic derivative of MDP, namely murabutide (MB), has been found to present interesting pharmacological properties and to suppress HIV-1 replication in monocyte-derived macrophages (MDM). We have addressed the signaling events activated in MDM following stimulation with either MB or the potent immunostimulant LPS. We also examined whether signaling by muramyl peptides involves the use of cell surface receptors, including CD14 and Toll-like receptor 2 (TLR2) or TLR4 that are known to be signal-transducing receptors for other bacterial cell wall components. We demonstrate that, unlike LPS, the safe immunomodulator MB selectively activates extracellular signal-regulated kinases (Erk) 1/2, in the absence of detectable Jun N-terminal kinase (JNK) or p38 mitogen-activated kinase activation. Furthermore, STAT1 activation but weak or no activation of STAT3 or STAT5 respectively, could be detected in MB-stimulated MDM. Using MonoMac6 cells, we observed high C/EBPbeta and AP-1 but weaker and transient NF-kappaB activation by MB.Moreover, the truncated form of C/EBPbeta, known to repress HIV-1 transcription, was detected in extracts from MB-treated THP-1 cells. Surprisingly, neither MB nor MDP were able to transduce signals via CD14 and TLR2 or 4. These findings present major differences in the early cell activation process between LPS and muramyl peptides, and strongly argue for the implication of co-receptors other than TLR2 and TLR4 in mediating the signaling events induced by defined subunits of bacterial peptidoglycans.
Vidal
V F
VF
Laboratory of Molecular Immunology of infection and Inflammation, Institut Pasteur de Lille, Lille, France.
Castéran
N
N
Riendeau
C J
CJ
Kornfeld
H
H
Darcissac
E C
EC
Capron
A
A
Bahr
G M
GM
D000119:Acetylmuramyl-Alanyl-Isoglutamine / Q000031:analogs & derivatives / Q000494:pharmacology*; D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D019380:Anti-HIV Agents / Q000494:pharmacology*; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism*; D016466:CHO Cells; D002460:Cell Line; D002478:Cells, Cultured; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000378:metabolism*; D029721:Drosophila Proteins; D004789:Enzyme Activation; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000502:physiology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009000:Monocytes / Q000276:immunology; D010766:Phosphorylation; D011956:Receptors, Cell Surface / Q000502:physiology; D050794:STAT1 Transcription Factor; D015398:Signal Transduction; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D015534:Trans-Activators / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism
D000276:Adjuvants, Immunologic; D019380:Anti-HIV Agents; D022782:CCAAT-Enhancer-Binding Protein-beta; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018950:Lipopolysaccharide Receptors; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D015534:Trans-Activators; D018808:Transcription Factor AP-1; D000119:Acetylmuramyl-Alanyl-Isoglutamine; C033575:murabutide; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases