CpG-DNA-specific activation of antigen-presenting cells requires stress kinase activity and is preceded by non-specific endocytosis and endosomal maturation.
Unmethylated CpG motifs in bacterial DNA, plasmid DNA and synthetic oligodeoxynucleotides (CpG ODN) activate dendritic cells (DC) and macrophages in a CD40-CD40 ligand-independent fashion. To understand the molecular mechanisms involved we focused on the cellular uptake of CpG ODN, the need for endosomal maturation and the role of the stress kinase pathway. Here we demonstrate that CpG-DNA induces phosphorylation of Jun N-terminal kinase kinase 1 (JNKK1/SEK/MKK4) and subsequent activation of the stress kinases JNK1/2 and p38 in murine macrophages and dendritic cells. This leads to activation of the transcription factor activating protein-1 (AP-1) via phosphorylation of its constituents c-Jun and ATF2. Moreover, stress kinase activation is essential for CpG-DNA-induced cytokine release of tumor necrosis factor alpha (TNFalpha) and interleukin-12 (IL-12), as inhibition of p38 results in severe impairment of this biological response. We further demonstrate that cellular uptake via endocytosis and subsequent endosomal maturation is essential for signalling, since competition by non-CpG-DNA or compounds blocking endosomal maturation such as chloroquine or bafilomycin A prevent all aspects of cellular activation. The data suggest that endosomal maturation is required for translation of intraendosomal CpG ODN sequences into signalling via the stress kinase pathway, where p38 kinase activation represents an essential step in CpG-ODN-triggered activation of antigen-presenting cells.
Häcker
H
H
Institute of Medical Microbiology, Immunology and Hygiene, Technische Universität München, Trogerstrasse 9, D-81675 Munich, Germany.
Mischak
H
H
Miethke
T
T
Liptay
S
S
Schmid
R
R
Sparwasser
T
T
Heeg
K
K
Lipford
G B
GB
Wagner
H
H
D051698:Activating Transcription Factor 2; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D002738:Chloroquine / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D019175:DNA Methylation; D004269:DNA, Bacterial / Q000276:immunology / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism*; D004789:Enzyme Activation / Q000235:genetics; D048031:JNK Mitogen-Activated Protein Kinases; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases; D009843:Oligoribonucleotides / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation; D015398:Signal Transduction / Q000235:genetics; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases
D051698:Activating Transcription Factor 2; C497106:Atf2 protein, mouse; D017362:Cyclic AMP Response Element-Binding Protein; D016207:Cytokines; D004269:DNA, Bacterial; D009843:Oligoribonucleotides; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D002738:Chloroquine; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases