CRAC channels are required for [Ca2 +]i oscillations and c-fos gene expression after muscarinic acetylcholine receptor activation in leukemic T cells.

Aims T lymphocytes express muscarinic acetylcholine receptors (mAChRs) involved in regulating their proliferation, differentiation and cytokine release. Activation of M 1 , M 3 or M 5 mAChRs increases the intracellular Ca 2 + concentration ([Ca 2 + ] i ) through inositol-1,4,5-phosphate (IP 3 )-mediated Ca 2 + release from endoplasmic reticulum Ca 2 + stores. In addition, T lymphocytes express Ca 2 + -release activated Ca 2 + (CRAC) channels to induce Ca 2 + influx and to regulate diverse immune functions. Our aim in the present study was to assess the role of CRAC channels during mAChR activation in the Ca 2 + -dependent transduction that contributes to the regulation of T cell function. Main methods Changes in [Ca 2 + ] i following mAChR activation on human leukemic T cells, CCRF-CEM (CEM), were monitored using fura-2, based on the ratio of 510 nm fluorescences elicited by excitation at 340 nm and 380 nm ( R 340/380 ). Key findings We demonstrate that CEM cells express mainly M 3 and M 5 mAChRs, but little the M 1 subtype, and that oxotremorine-M (Oxo-M), an mAChR agonist, induces an initial transient increase in [Ca 2 + ] i followed by repetitive [Ca 2 + ] i oscillations. Removing extracellular Ca 2 + or pharmacological blockade of CRAC channels abolished the [Ca 2 + ] i oscillations without affecting the initial [Ca 2 + ] i transient induced by Oxo-M. Moreover, CRAC channel blockade also suppressed Oxo-M-induced c-fos and interleukin-2 expression. Significance These results suggest that upon M 3 or M 5 mAChR activation, IP 3 -mediated Ca 2 + release induces extracellular Ca 2 + influx through CRAC channels, which generates repetitive [Ca 2 + ] i oscillations and, in turn, enhances c-fos gene expression in T lymphocytes. [ABSTRACT FROM AUTHOR]