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Protein kinase Cδ oxidation contributes to ERK inactivation in lupus T cells

Gabriela J Gorelik1, Sushma Yarlagadda, Dipak R Patel

  • 1University of Michigan, Ann Arbor, MI 48109-2200, USA. ggorelik@umich.edu

Arthritis and Rheumatism
|May 3, 2012
PubMed
Abstract

Insights

Nitration of protein kinase Cδ (PKCδ) by oxidative stress impairs T cell signaling in lupus. This nitration prevents PKCδ phosphorylation, contributing to the immune dysregulation seen in lupus patients.

Area of Science:

  • Immunology
  • Molecular Biology
  • Biochemistry

Background:

  • Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by immune system dysregulation.
  • Impaired ERK pathway signaling in CD4+ T cells from lupus patients leads to decreased DNA methyltransferase expression, DNA demethylation, and overexpression of immune genes, driving autoimmunity.
  • The precise mechanisms causing impaired ERK pathway signaling, specifically the defect in protein kinase Cδ (PKCδ) T505 phosphorylation, in lupus T cells remain unclear.

Purpose of the Study:

  • To investigate the hypothesis that nitration of PKCδ inactivates the enzyme, contributing to impaired ERK pathway signaling in T cells from lupus patients.
  • To elucidate the role of oxidative stress, specifically protein nitration, in the pathogenesis of lupus T cell dysfunction.

Main Methods:

  • CD4+ T cells were isolated from patients with active lupus and healthy controls.
  • Cells were stimulated with phorbol myristate acetate (PMA) and analyzed for signaling protein levels, nitration, and phosphorylation using immunoprecipitation and immunoblotting.
  • Peroxynitrite was used to induce PKCδ nitration in vitro to mimic conditions observed in lupus.

Main Results:

  • In vitro treatment of CD4+ T cells with peroxynitrite led to PKCδ nitration, inhibiting T505 phosphorylation and ERK pathway signaling, mirroring findings in lupus T cells.
  • Patients with active lupus exhibited elevated levels of nitrated PKCδ in their T cells compared to controls, with levels correlating with disease activity.
  • Antinitrotyrosine immunoprecipitation confirmed that nitrated PKCδ, unlike unmodified PKCδ, was resistant to PMA-induced T505 phosphorylation.

Conclusions:

  • Oxidative stress-induced nitration of PKCδ is a key mechanism that prevents its phosphorylation, leading to decreased ERK signaling in lupus T cells.
  • These findings establish PKCδ as a critical molecular link connecting oxidative stress to T cell epigenetic alterations and immune dysregulation in lupus.
  • Targeting oxidative stress pathways may offer a therapeutic strategy for lupus by restoring T cell signaling and function.

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