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. Issue 9 (September 2014)

• Record Type: Journal Article
• Authors: Negoro, T.; Shimizu, S.; Narushima, M.; Banham, A. H.; Wakabayashi, H.; Takayanagi, R.; Hagiwara, T.; Roncador, G.; Osabe, T.; Yanai, T.; Kin, M.; Ikeda, K.; Endo, A.; Akiyama, H.; Nakano, Y.
• Is Part Of: Clinical & experimental allergy. Volume 44:Issue 9(2014:Sep.)
• Page Start: 1154
• Page End: 1169
• Publication Date: 2014-09
• Subjects: Allergy -- Periodicals; Immunology -- Periodicals; 616.97
• DOI: 10.1111/cea.12375
• Languages: English
• ISSNs: 0954-7894

Abstract

<abstract abstract-type="main" id="cea12375-abs-0001"> <title>Summary</title> <sec id="cea12375-sec-0001" sec-type="section"> <title>Background</title> <p>Regulatory T cells (T<sub>regs</sub>) are activated during anergy in response to T cell receptor (TCR) activation and functional immune suppression. Anergy of paediatric T<sub>regs</sub> is partially dependent on intracellular calcium mobility; following TCR activation, T<sub>regs</sub> do not exhibit increased intracellular Ca<sup>2+</sup> concentration ([Ca<sup>2+</sup>]<sub>i</sub>).</p> </sec> <sec id="cea12375-sec-0002" sec-type="section"> <title>Objective</title> <p>We determined whether [Ca<sup>2+</sup>]<sub>i</sub> in adult T<sub>regs</sub> defined their anergy, if intracellular Ca<sup>2+</sup> movement was linked to regulatory functions, whether [Ca<sup>2+</sup>]<sub>i</sub> was indicative of asthma pathology, and the potential molecular mechanism responsible for Ca<sup>2+</sup> movement in T<sub>regs</sub>.</p> </sec> <sec id="cea12375-sec-0003" sec-type="section"> <title>Methods</title> <p>T<sub>regs</sub> 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<sup>2+</sup> response of Fura‐2‐labelled cells was measured using a video image analysis system. To analyse the functions of T<sub>regs</sub> at the molecular level, we generated Jurkat Tet‐On<sup>®</sup> clones with doxycycline (Dox)‐induced forkhead box P3 (FOXP3) protein expression.</p> </sec> <sec id="cea12375-sec-0004" sec-type="section"> <title>Results</title> <p>CD4<sup>+</sup>CD25<sup>+</sup>CD127<sup>−/low</sup> T<sub>regs</sub> from participants without asthma did not elicit Ca<sup>2+</sup> influx in response to TCR activation, exhibited little proliferation and suppressed proliferation of CD4<sup>+</sup>CD25<sup>−</sup> T cells. In contrast, under similar conditions, T<sub>regs</sub> from patients with asthma exhibited increased [Ca<sup>2+</sup>]<sub>i</sub> and robust proliferation with partial loss of regulatory functions. FOXP3 protein levels in Tet‐On<sup>®</sup> clones were high after both 2‐ and 5‐day Dox treatment; however, 5‐day cells were comparable with T<sub>regs</sub> from patients with asthma, whereas 2‐day cells were similar to T<sub>regs</sub> from participants without asthma. Increasing [Ca<sup>2+</sup>]<sub>i</sub> induced a high level of receptor for activated C kinase 1 (RACK1) expression in 5‐day cells.</p> </sec> <sec id="cea12375-sec-0005" sec-type="section"> <title>Conclusions and Clinical Relevance</title> <p>We confirmed that T<sub>regs</sub> in patients with asthma are functionally impaired and that the abnormal regulatory functions of these cells can be analysed by [Ca<sup>2+</sup>]<sub>i</sub> following TCR engagement. Furthermore, the impaired functioning of T<sub>regs</sub> evident in patients with asthma may be due to a high level of RACK1.</p> </sec> </abstract>