Identification and Functional Characterization of Voltage-dependent Calcium Channels in T Lymphocytes

Abstract

In T lymphocytes, sustained calcium (Ca 2؉ ) influx through Ca 2؉ channels localized in the plasma membrane is critical for T cell activation and proliferation. Previous studies indicated that voltage-dependent Ca 2؉ channels (VDCCs) play a role in Ca 2؉ mobilization during T lymphocyte activation. However, the role of VDCCs in otherwise nonexcitable cells is still poorly understood. We used RT-PCR to identify a transcript encoding the pore-forming ␣ 1F -subunit of an L-type Ca 2؉ channel in T lymphocytes. Its identity was confirmed by DNA sequencing. To further investigate the contribution of Ca 2؉ influx through VDCCs, we assessed the effects of the 1,4-dihydropyridine L-type Ca 2؉ channel agonist, (؉/؊) Bay K 8644, and antagonist, nifedipine, on the human Jurkat T cell leukemia line, human peripheral blood T lymphocytes and mouse splenocytes. We found that treatment of T lymphocytes with (؉/؊) Bay K 8644 increased intracellular Ca 2؉ and induced the activation of phosphoextracellular-regulated kinase 1/2 (Erk1/2), whereas nifedipine blocked Ca 2؉ influx, the activity of Erk1/2 and nuclear factor of activated T cells (NFAT), interleukin-2 (IL-2) production, and IL-2 receptor expression. Nifedipine also significantly suppressed splenocyte proliferation in an in vitro mixed lymphocyte reaction and the proliferation of male antigen (H-Y)-specific T cell receptor-transgenic CD8 ؉ T cells in transplanted male mice in vivo. Taken together these novel findings indicate that an L-type Ca 2؉ channel plays a significant role in the Ca 2؉ influx pathways mediating T lymphocyte activation and proliferation in vitro and in vivo.

Non-voltage-gated L-type Ca2+ Channels in Human T Cells

“…Stimulation-A number of recent reports show that drugs active against L-type channels can inhibit Ca 2ϩ influx in nonexcitable cells (26,29). To eliminate the possibility of authentic voltage-gated Ca 2ϩ channels being expressed in Jurkat T lym-phocytes, cells were treated with 50 mM KCl to induce depolarization.…”

“…In our experiments, TCR cross-linking was initiated by the addition of OKT3, an anti-CD3⑀ antibody, which mimics the binding of foreign antigen to the TCR. Kotturi et al (29) found that the dihydropyridine L-type Ca 2ϩ channel antagonist nifedipine inhibited the anti-CD3-induced Ca 2ϩ flux in Jurkat T lymphocytes in a dose-dependent manner. We extended these observations using representative drugs from two other classes of L-type Ca 2ϩ channel antagonist.…”

“…Similar channels have been detected in T lymphocytes. Savignac et al (27) (29) showed the presence of an ␣ 1 1.4 transcript in Jurkat and provided some pharmacological data to indicate that a voltagegated Ca 2ϩ channel-related channel may have a role in T lymphocyte activation (29). These studies have not directly addressed the expression of a voltage-gated Ca 2ϩ channelrelated protein in human T lymphocytes.…”

Ca2+ signals and T lymphocytes “New mechanisms and functions in Ca2+ signalling”

“…This effect of dihydropyridine on lymphocytes K + channels, and the absence of any depolarisation-induced inward currents in lymphocytes is unfortunately frequently ignored (see e.g. (Kotturi et al, 2003)). More physiologically, it has been shown in human T lymphocytes as well as in T cell lines, that progesterone, by blocking voltage-dependent and Ca 2+ -dependent K + channels, depolarizes the cells and therefore reduces Ca 2+ rise after TCR stimulation, thereby inhibiting the calcineurindependent nuclear translocation of NFAT (Nuclear Factor of Activated T cells) (see below).…”

Dihydropyridine Receptors Are Selective Markers of Th2 Cells and Can Be Targeted to Prevent Th2-Dependent Immunopathological Disorders

“…Preliminary data indicate that the PCR products were related to ␣1C (cardiac-neuronal) and ␣ 1 D (neuroendocrine) subunits of L-type calcium channels in Th2 cells (M. Savignac, B. Gomes, D. Baup, C. Larroze, S. Narbonnet, M. Moreau, C. Leclerc, P. Paulet, D. Lagrange, B. Mariamé, et al, manuscript in preparation). Very recently, Kotturi et al (41) used nested RT-PCR to identify a transcript encoding the retinal ␣ 1 F subunit of L-type calcium channels in human and murine T cells. In addition, this study reported that DHPR agonist triggers a rise in [Ca 2ϩ ] i at concentrations equal or superior to 50 M and that nifedipine, a DHPR antagonist, reduced calcium signal, activation of the calcium-sensitive transcription factor NFAT, and IL-2 production by T cells.…”