Elevated receptor for activated C kinase 1 expression is involved in intracellular Ca2+ influx and potentially associated with compromised regulatory T cell function in patients with asthma

Clin Exp Allergy. 2014 Sep;44(9):1154-69. doi: 10.1111/cea.12375.

Abstract

Background: Regulatory T cells (T(regs)) are activated during anergy in response to T cell receptor (TCR) activation and functional immune suppression. Anergy of paediatric T(regs) is partially dependent on intracellular calcium mobility; following TCR activation, T(regs) do not exhibit increased intracellular Ca(2+) concentration ([Ca(2+) ](i)).

Objective: We determined whether [Ca(2+) ](i) in adult T(regs) defined their anergy, if intracellular Ca(2+) movement was linked to regulatory functions, whether [Ca(2+)](i) was indicative of asthma pathology, and the potential molecular mechanism responsible for Ca(2+) movement in T(regs).

Methods: T(regs) were purified by the magnetic bead method, and their regulatory functions were assessed by monitoring carboxyfluorescein succinimidyl ester-labelled responder T cell proliferation. The Ca(2+) response of Fura-2-labelled cells was measured using a video image analysis system. To analyse the functions of T(regs) at the molecular level, we generated Jurkat Tet-On(®) clones with doxycycline (Dox)-induced forkhead box P3 (FOXP3) protein expression.

Results: CD4(+) CD25(+) CD127(-/low) T(regs) from participants without asthma did not elicit Ca(2+) influx in response to TCR activation, exhibited little proliferation and suppressed proliferation of CD4(+) CD25(-) T cells. In contrast, under similar conditions, T(regs) from patients with asthma exhibited increased [Ca(2+)](i) and robust proliferation with partial loss of regulatory functions. FOXP3 protein levels in Tet-On(®) clones were high after both 2- and 5-day Dox treatment; however, 5-day cells were comparable with T(regs) from patients with asthma, whereas 2-day cells were similar to T(regs) from participants without asthma. Increasing [Ca(2+)](i) induced a high level of receptor for activated C kinase 1 (RACK1) expression in 5-day cells.

Conclusions and clinical relevance: We confirmed that T(regs) in patients with asthma are functionally impaired and that the abnormal regulatory functions of these cells can be analysed by [Ca(2+)](i) following TCR engagement. Furthermore, the impaired functioning of T(regs) evident in patients with asthma may be due to a high level of RACK1.

Keywords: FOXP3; RACK1; asthma; calcium; regulatory T cell.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Cortex Hormones / administration & dosage
  • Adrenal Cortex Hormones / therapeutic use
  • Adult
  • Aged
  • Antigens, Surface / metabolism
  • Asthma / diagnosis
  • Asthma / drug therapy
  • Asthma / genetics
  • Asthma / immunology*
  • Asthma / metabolism*
  • Calcium / metabolism*
  • Case-Control Studies
  • Cell Line
  • Cell Proliferation
  • Female
  • Forkhead Transcription Factors / genetics
  • Forkhead Transcription Factors / metabolism
  • Gene Expression
  • Humans
  • Immunophenotyping
  • Intracellular Space / metabolism
  • Lymphocyte Activation
  • Male
  • Middle Aged
  • Phenotype
  • Receptors for Activated C Kinase
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism*
  • Risk Factors
  • T-Lymphocytes, Regulatory / immunology*
  • T-Lymphocytes, Regulatory / metabolism*

Substances

  • Adrenal Cortex Hormones
  • Antigens, Surface
  • FOXP3 protein, human
  • Forkhead Transcription Factors
  • Receptors for Activated C Kinase
  • Receptors, Cell Surface
  • Calcium