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Osteopontin and protein kinase C regulate PDLIM2 activation and STAT1 ubiquitination in LPS-treated murine

Hongtao Guo1, Zhiyong Mi, Dawn E Bowles

  • 1Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA.

The Journal of Biological Chemistry
|October 5, 2010
PubMed

Insights

Osteopontin (OPN) promotes the degradation of Signal Transducer and Activator of Transcription 1 (STAT1) via PDLIM2. This OPN-PDLIM2 pathway is crucial for regulating STAT1-mediated inflammatory responses during sepsis.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cellular Signaling

Background:

  • STAT1 levels are critical in inflammation but its degradation pathways are unclear.
  • Existing mechanisms regulate STAT1 activity but not its degradation.
  • Osteopontin (OPN) was previously shown to induce STAT1 ubiquitination and proteasomal degradation via PDLIM2.

Purpose of the Study:

  • To further characterize OPN-dependent activation of PDLIM2 in macrophages.
  • To identify key regulatory sites and mechanisms in the OPN-PDLIM2-STAT1 axis.
  • To investigate the functional consequences of PDLIM2-mediated STAT1 degradation in vitro and in vivo.

Main Methods:

  • Utilized LPS-stimulated RAW264.7 murine macrophages and murine models.
  • Employed phospho-mutants and phospho-mimetic constructs of PDLIM2.
  • Performed ubiquitination assays, reporter assays, and chromatin immunoprecipitation.

Main Results:

  • Identified Serine 137 in PDLIM2 as a crucial phosphorylation site for STAT1 ubiquitination, dependent on OPN.
  • Confirmed PDLIM2's role in Ub-STAT1 formation and degradation using various constructs.
  • Demonstrated OPN's necessity for PDLIM2 phosphorylation and STAT1 ubiquitination in a murine sepsis model.

Conclusions:

  • OPN induces PDLIM2 phosphorylation at Serine 137, facilitating STAT1 ubiquitination and degradation.
  • The OPN-PDLIM2 pathway is essential for regulating STAT1-mediated inflammatory responses.
  • This pathway plays a significant role in inflammatory conditions, including sepsis.

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