The cell-specific induction of CXC chemokine ligand 9 mediated by IFN-gamma in microglia of the central nervous system is determined by the myeloid transcription factor PU.1.
The IFN-gamma-inducible chemokines CXCL9 and CXCL10 are implicated in the pathogenesis of T cell-mediated immunity in the CNS. However, in various CNS immune pathologies the cellular localization of these chemokines differs, with CXCL9 produced by macrophage/microglia whereas CXCL10 is produced by both macrophage/microglia and astrocytes. In this study, we determined the mechanism for the microglial cell-restricted expression of the Cxcl9 gene induced by IFN-gamma. In cultured glial cells, the induction of the CXCL9 (in microglia) and CXCL10 (in microglia and astrocytes) mRNAs by IFN-gamma was not inhibited by cycloheximide. Of various transcription factors involved with IFN-gamma-mediated gene regulation, PU.1 was identified as a constitutively expressed NF in microglia but not in astrocytes. STAT1 and PU.1 bound constitutively to the Cxcl9 gene promoter in microglia, and this increased significantly following IFN-gamma treatment with IFN regulatory factor-8 identified as an additional late binding factor. However, in astrocytes, STAT1 alone bound to the Cxcl9 gene promoter. STAT1 was critical for IFN-gamma induction of both the Cxcl9 and Cxcl10 genes in microglia and in microglia and astrocytes, respectively. The small interfering RNA-mediated knockdown of PU.1 in microglia markedly impaired IFN-gamma-induced CXCL9 but not STAT1 or IFN regulatory factor-8. Cells of the D1A astrocyte line showed partial reprogramming to a myeloid-like phenotype posttransduction with PU.1 and, in addition to the expression of CD11b, acquired the ability to produce CXCL9 in response to IFN-gamma. Thus, PU.1 not only is crucial for the induction of CXCL9 by IFN-gamma in microglia but also is a key determinant factor for the cell-specific expression of this chemokine by these myeloid cells.
Ellis
Sally L
SL
School of Molecular Bioscience and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia.
Gysbers
Vanessa
V
Manders
Peter M
PM
Li
Wen
W
Hofer
Markus J
MJ
Müller
Marcus
M
Campbell
Iain L
IL
D000818:Animals; D002460:Cell Line; D019070:Cell Lineage / Q000276:immunology; D002478:Cells, Cultured; D002490:Central Nervous System / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D054357:Chemokine CXCL10 / Q000096:biosynthesis; D054370:Chemokine CXCL9 / Q000096:biosynthesis*; D007371:Interferon-gamma / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017628:Microglia / Q000276:immunology* / Q000378:metabolism*; D022423:Myeloid Cells / Q000276:immunology* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D050794:STAT1 Transcription Factor / Q000502:physiology; D015534:Trans-Activators / Q000502:physiology*; D000099232:Proto-Oncogene Protein Spi-1
D054357:Chemokine CXCL10; D054370:Chemokine CXCL9; D007371:Interferon-gamma; D011518:Proto-Oncogene Proteins; D050794:STAT1 Transcription Factor; D015534:Trans-Activators; D000099232:Proto-Oncogene Protein Spi-1; C485433:Cxcl10 protein, mouse; C485969:Cxcl9 protein, mouse; C494080:Stat1 protein, mouse