A reducing milieu renders cofilin insensitive to phosphatidylinositol 4,5-bisphosphate (PIP2) inhibition

Bianca Schulte, Isabel John, Bernd Simon, Christoph Brockmann, Stefan A Oelmeier, Beate Jahraus, Henning Kirchgessner, Selina Riplinger, Teresa Carlomagno, Guido H Wabnitz, Yvonne Samstag

Research output: Contribution to journalArticlepeer-review

Abstract

Oxidative stress can lead to T cell hyporesponsiveness. A reducing micromilieu (e.g. provided by dendritic cells) can rescue T cells from such oxidant-induced dysfunction. However, the reducing effects on proteins leading to restored T cell activation remained unknown. One key molecule of T cell activation is the actin-remodeling protein cofilin, which is dephosphorylated on serine 3 upon T cell costimulation and has an essential role in formation of mature immune synapses between T cells and antigen-presenting cells. Cofilin is spatiotemporally regulated; at the plasma membrane, it can be inhibited by phosphatidylinositol 4,5-bisphosphate (PIP2). Here, we show by NMR spectroscopy that a reducing milieu led to structural changes in the cofilin molecule predominantly located on the protein surface. They overlapped with the PIP2- but not actin-binding sites. Accordingly, reduction of cofilin had no effect on F-actin binding and depolymerization and did not influence the cofilin phosphorylation state. However, it did prevent inhibition of cofilin activity through PIP2. Therefore, a reducing milieu may generate an additional pool of active cofilin at the plasma membrane. Consistently, in-flow microscopy revealed increased actin dynamics in the immune synapse of untransformed human T cells under reducing conditions. Altogether, we introduce a novel mechanism of redox regulation: reduction of the actin-remodeling protein cofilin renders it insensitive to PIP2 inhibition, resulting in enhanced actin dynamics.

Original languageEnglish
Pages (from-to)29430-9
Number of pages10
JournalThe Journal of biological chemistry
Volume288
Issue number41
DOIs
Publication statusPublished - 11 Oct 2013

Keywords

  • Actin Depolymerizing Factors/chemistry
  • Actins/metabolism
  • Blotting, Western
  • Cell Line, Tumor
  • Cell Membrane/metabolism
  • Cells, Cultured
  • Cysteine/chemistry
  • Humans
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Molecular Dynamics Simulation
  • Mutation
  • Oxidation-Reduction
  • Phosphatidylinositol 4,5-Diphosphate/chemistry
  • Phosphorylation
  • Polymerization
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Tertiary
  • T-Lymphocytes/metabolism

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