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Stress-induced phosphorylation of STAT1 at Ser727 requires p38 mitogen-activated protein kinase whereas IFN-gamma uses a different signaling pathway.

Abstract：

:STAT1 is an essential transcription factor for macrophage activation by IFN-gamma and requires phosphorylation of the C-terminal Ser727 for transcriptional activity. In macrophages, Ser727 phosphorylation in response to bacterial lipopolysaccharide (LPS), UV irradiation, or TNF-alpha occurred through a signaling path sensitive to the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580 whereas IFN-gamma-mediated Ser727 phosphorylation was not inhibited by the drug. Consistently, SB203580 did not affect IFN-gamma-mediated, Stat1-dependent transcription but inhibited its enhancement by LPS. Furthermore, LPS, UV irradiation, and TNF-alpha caused activation of p38 MAPK whereas IFN-gamma did not. An essential role for p38 MAPK activity in STAT1 Ser727 phosphorylation was confirmed by using cells expressing an SB203580-resistant p38 MAPK. In such cells, STAT1 Ser727 phosphorylation in response to UV irradiation was found to be SB203580 insensitive. Targeted disruption of the mapkap-k2 gene, encoding a kinase downstream of p38 MAPK with a key role in LPS-stimulated TNF-alpha production and stress-induced heat shock protein 25 phosphorylation, was without a significant effect on UV-mediated Ser727 phosphorylation. The recombinant Stat1 C terminus was phosphorylated in vitro by p38MAPKalpha and beta but not by MAPK-activated protein kinase 2. Janus kinase 2 activity, previously reported to be required for IFN-gamma-mediated Ser727 phosphorylation, was not needed for LPS-mediated Ser727 phosphorylation, and activation of Janus kinase 2 did not cause the appearance of STAT1 Ser727 kinase activity. Our data suggest that STAT1 is phosphorylated at Ser727 by a stress-activated signaling pathway either through p38 MAPK directly or through an unidentified kinase downstream of p38MAPK.

journal_name

Proc Natl Acad Sci U S A

journal_title

Proceedings of the National Academy of Sciences of the United States of America

authors

Kovarik P,Stoiber D,Eyers PA,Menghini R,Neininger A,Gaestel M,Cohen P,Decker T

doi

10.1073/pnas.96.24.13956

keywords:

subject

Has Abstract

pub_date

1999-11-23 00:00:00

pages

13956-61

issue

eissn

0027-8424

issn

1091-6490

journal_volume

pub_type

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Stress-induced phosphorylation of STAT1 at Ser727 requires p38 mitogen-activated protein kinase whereas IFN-gamma uses a different signaling pathway.