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

Published

Journal Article

The molecular pathways regulating signal transducer and activator of transcription 1 (STAT1) levels in states of inflammation are incompletely understood. The suppressor of cytokine signaling, protein inhibitor of STAT, and SHP-1/2 tyrosine phosphatases ultimately regulate activity of STAT molecules. However, these mechanisms do not degrade STAT proteins. In this regard, using a murine macrophage model of LPS stimulation, we previously demonstrated that osteopontin (OPN) increased STAT1 ubiquitination and 26 S proteasome degradation via the ubiquitin E3 ligase, PDLIM2. In this study, we further characterize OPN-dependent activation of PDLIM2 in a model of LPS-stimulated RAW264.7 murine macrophages. We identify serine 137 as a protein kinase C-phosphorylation site in PDLIM2 that is required for ubiquitination of STAT1. PDLIM2 phosphorylation requires OPN expression. Using phospho-mutants and phospho-mimetic constructs of PDLIM2, our in vivo and in vitro ubiquitination studies confirm the role of PDLIM2 in formation and degradation of Ub-STAT1. The functional consequences of PDLIM2-mediated STAT1 degradation were confirmed using an IFN-γ-regulated transcription factor STAT1α reporter construct and chromatin immunoprecipitation assay for the inducible nitric-oxide synthase promoter. In a murine cecal ligation and puncture model of sepsis in wild-type and OPN (-/-) animals, OPN was necessary for PDLIM2 serine phosphorylation and STAT1 ubiquitination in bone marrow macrophages. We conclude that OPN and PDLIM2 are important regulators of STAT1-mediated inflammatory responses.

Full Text

Duke Authors

Cited Authors

  • Guo, H; Mi, Z; Bowles, DE; Bhattacharya, SD; Kuo, PC

Published Date

  • November 26, 2010

Published In

Volume / Issue

  • 285 / 48

Start / End Page

  • 37787 - 37796

PubMed ID

  • 20889505

Pubmed Central ID

  • 20889505

Electronic International Standard Serial Number (EISSN)

  • 1083-351X

Digital Object Identifier (DOI)

  • 10.1074/jbc.M110.161869

Language

  • eng

Conference Location

  • United States