title: Interleukin-1 receptor-associated kinase 2- and protein kinase D1-dependent regulation of IRAK-monocyte expression by CpG DNA.
abstract: As a part of the negative feedback mechanism, CpG DNA induces IRAK-M expression in monocytic cells. In the present study we investigated a biochemical signaling pathway and the transcription factors responsible for CpG DNA-mediated Irak-m gene expression. CpG DNA-induced Irak-m expression did not require new protein synthesis and was regulated at the transcriptional level through an endosomal pH-sensitive TLR9/MyD88 signaling pathway. Over-expression of the dominant negative (DN) form of or gene-specific knockdown of signaling modulators in the TLR9 pathway demonstrated that IRAK4, IRAK1, IRAK2, and PKD1 are required for Irak-m transcription induced by CpG DNA. Over-expression of DN-IRAK1 only partially, but significantly, inhibited CpG DNA-induced Irak-m promoter activity. While IRAK1 was critical for the initial phase, IRAK2 was required for the late phase of TLR9 signaling by sustaining activation of PKD1 that leads to activation of NF-κB and MAPKs. Irak-m promoter-luciferase reporters with alterations in the predicted cis-acting transcriptional regulatory elements revealed that the NF-κB consensus site in the Irak-m promoter region is absolutely required for Irak-m gene expression. AP-1 and CREB binding sites also contributed to the optimal Irak-m expression by CpG DNA. Collectively, our results demonstrate that IRAK2 plays a key role in the TLR9-mediated transcriptional regulation of Irak-m expression by sustaining activation of PKD1 and NF-κB.
authors.affiliation: Children's Foundation Research Institute at Le Bonheur Children's Hospital and Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America.
authors.forename: Young-In
authors.initials: YI
authors.lastname: Kim
authors.forename: Jeoung-Eun
authors.initials: JE
authors.lastname: Park
authors.forename: Ki Han
authors.initials: KH
authors.lastname: Kwon
authors.forename: Cheol Yi
authors.initials: CY
authors.lastname: Hong
authors.forename: Ae-Kyung
authors.initials: AK
authors.lastname: Yi
mesh_terms: D000818:Animals; D002460:Cell Line; D018899:CpG Islands; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004247:DNA / Q000235:genetics*; D005786:Gene Expression Regulation / Q000235:genetics*; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011493:Protein Kinase C / Q000378:metabolism*; D015398:Signal Transduction; D051217:Toll-Like Receptor 9 / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D008024:Ligands; D016328:NF-kappa B; D051217:Toll-Like Receptor 9; D018808:Transcription Factor AP-1; D004247:DNA; C089212:protein kinase D; D053592:Interleukin-1 Receptor-Associated Kinases; C507772:Irak3 protein, mouse; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases