title: A reducing milieu renders cofilin insensitive to phosphatidylinositol 4,5-bisphosphate (PIP2) inhibition.
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.
authors.affiliation: From the Institute for Immunology, Ruprecht Karls University, D-69120 Heidelberg, Germany.
authors.forename: Bianca
authors.initials: B
authors.lastname: Schulte
authors.forename: Isabel
authors.initials: I
authors.lastname: John
authors.forename: Bernd
authors.initials: B
authors.lastname: Simon
authors.forename: Christoph
authors.initials: C
authors.lastname: Brockmann
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Oelmeier
authors.forename: Beate
authors.initials: B
authors.lastname: Jahraus
authors.forename: Henning
authors.initials: H
authors.lastname: Kirchgessner
authors.forename: Selina
authors.initials: S
authors.lastname: Riplinger
authors.forename: Teresa
authors.initials: T
authors.lastname: Carlomagno
authors.forename: Guido H
authors.initials: GH
authors.lastname: Wabnitz
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Samstag
mesh_terms: D051339:Actin Depolymerizing Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D003545:Cysteine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009154:Mutation; D010084:Oxidation-Reduction; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D058105:Polymerization; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013601:T-Lymphocytes / Q000378:metabolism*
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D019269:Phosphatidylinositol 4,5-Diphosphate; D003545:Cysteine
keywords: Cofilin; Oxidation-Reduction; Phosphatidylinositol Signaling; Redox Regulation; T Cell