Specific Inhibitors of p38 and Extracellular Signal‐Regulated Kinase Mitogen‐Activated Protein Kinase Pathways Block Inducible Nitric Oxide Synthase and Tumor Necrosis Factor Accumulation in Murine Macrophages Stimulated with Lipopolysaccharide and Interferon‐γ

STAT1 (signal transducer and activator of transcription 1) is a critical mediator of IFN-γ (interferon-γ)-induced gene responses, and its function is regulated through phosphorylation of Tyr701 and Ser727. MAPK (mitogen-activated protein kinase) pathways mediate phosphorylation of Ser727 in response to microbial infections, stress stimuli and growth factors. Recently, STAT1 was found to become modified by PIAS (protein inhibitor of activated STAT)-mediated SUMO-1 (small ubiquitin-related modifier-1) conjugation at Lys703, but the regulation of this modification is largely unknown. Here, we have investigated the role of MAPK-induced Ser727 phosphorylation in regulation of STAT1 SUMOylation. Activation of the p38MAPK pathway by upstream activating kinase, MKK6 (MAPK kinase-6) or osmotic stress enhanced the SUMOylation of STAT1, which was counteracted by the p38MAPK inhibitor SB202190 or by dominant-negative p38MAPK. Activation of the ERK1/2 (extracellular-signal-regulated kinase 1/2) pathway by Raf-1 also enhanced Ser727 phosphorylation and SUMOylation of STAT1, and this induction was counteracted by PD98059 inhibitor. Mutation of Ser727 to alanine abolished the p38MAPK-induced SUMOylation. Furthermore, S727D and S727E mutations, which mimic the phosphorylation of Ser727, enhanced the basal SUMOylation of STAT1 and interaction between PIAS1 and STAT1. Taken together, these results identify Ser727 phosphorylation as a regulator of STAT1 SUMOylation and highlight the central role of Ser727 in co-ordination of STAT1 functions in cellular responses.

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p38 mitogen-activated protein kinase mediates lipopolysaccharide, not interferon-γ, -induced inducible nitric oxide synthase expression in mouse BV2 microglial cells

Neuroscience Letters ◽

10.1016/s0304-3940(02)00218-5 ◽

2002 ◽

Vol 325 (1) ◽

pp. 9-12 ◽

Cited By ~ 55

Author(s):

Inn-Oc Han ◽

Ki-Wan Kim ◽

Jong Hoon Ryu ◽

Won-Ki Kim

Keyword(s):

Nitric Oxide ◽

Protein Kinase ◽

Nitric Oxide Synthase ◽

Inducible Nitric Oxide Synthase ◽

Interferon Γ ◽

Mitogen Activated Protein Kinase ◽

Mitogen Activated Protein ◽

Oxide Synthase ◽

Bv2 Microglial Cells ◽

Inducible Nitric Oxide

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Extracellular Signal-regulated Kinase Phosphorylates Tumor Necrosis Factor α-converting Enzyme at Threonine 735: A Potential Role in Regulated Shedding

Molecular Biology of the Cell ◽

10.1091/mbc.01-11-0561 ◽

2002 ◽

Vol 13 (6) ◽

pp. 2031-2044 ◽

Cited By ~ 211

Author(s):

Elena Dı́az-Rodrı́guez ◽

Juan Carlos Montero ◽

Azucena Esparı́s-Ogando ◽

Laura Yuste ◽

Atanasio Pandiella

Keyword(s):

Tumor Necrosis Factor ◽

Tumor Necrosis ◽

Tumor Necrosis Factor Α ◽

Converting Enzyme ◽

Erk Activation ◽

Extracellular Signal Regulated Kinase ◽

Extracellular Signal ◽

Mitogen Activated Protein ◽

Factor Α ◽

Necrosis Factor

The ectodomain of certain transmembrane proteins can be released by the action of cell surface proteases, termed secretases. Here we have investigated how mitogen-activated protein kinases (MAPKs) control the shedding of membrane proteins. We show that extracellular signal-regulated kinase (Erk) acts as an intermediate in protein kinase C-regulated TrkA cleavage. We report that the cytosolic tail of the tumor necrosis factor α-converting enzyme (TACE) is phosphorylated by Erk at threonine 735. In addition, we show that Erk and TACE associate. This association is favored by Erk activation and by the presence of threonine 735. In contrast to the Erk route, the p38 MAPK was able to stimulate TrkA cleavage in cells devoid of TACE activity, indicating that other proteases are also involved in TrkA shedding. These results demonstrate that secretases are able to discriminate between the different stimuli that trigger membrane protein ectodomain cleavage and indicate that phosphorylation by MAPKs may regulate the proteolytic function of membrane secretases.

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