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A voltage-gated sodium channel is essential for the positive selection of CD4(+) T cells.

ABSTRACT: The sustained entry of Ca(2+) into CD4(+)CD8(+) double-positive thymocytes is required for positive selection. Here we identified a voltage-gated Na(+) channel (VGSC) that was essential for positive selection of CD4(+) T cells. Pharmacological inhibition of VGSC activity inhibited the sustained Ca(2+) influx induced by positively selecting ligands and the in vitro positive selection of CD4(+) but not CD8(+) T cells. In vivo short hairpin RNA (shRNA)-mediated knockdown of the gene encoding a regulatory ?-subunit of a VGSC specifically inhibited the positive selection of CD4(+) T cells. Ectopic expression of VGSC in peripheral AND CD4(+) T cells bestowed the ability to respond to a positively selecting ligand, which directly demonstrated that VGSC expression was responsible for the enhanced sensitivity. Thus, active VGSCs in thymocytes provide a mechanism by which a weak positive selection signal can induce the sustained Ca(2+) signals required for CD4(+) T cell development.

SUBMITTER: Lo WL

PROVIDER: S-EPMC3426661 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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A voltage-gated sodium channel is essential for the positive selection of CD4(+) T cells.

Lo Wan-Lin WL Donermeyer David L DL Allen Paul M PM

Nature immunology 20120729 9

The sustained entry of Ca(2+) into CD4(+)CD8(+) double-positive thymocytes is required for positive selection. Here we identified a voltage-gated Na(+) channel (VGSC) that was essential for positive selection of CD4(+) T cells. Pharmacological inhibition of VGSC activity inhibited the sustained Ca(2+) influx induced by positively selecting ligands and the in vitro positive selection of CD4(+) but not CD8(+) T cells. In vivo short hairpin RNA (shRNA)-mediated knockdown of the gene encoding a regu ...[more]

PMID: 22842345

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Project description:Background:Voltage-gated sodium (NaV) channels are heteromeric proteins consisting of a single pore forming ?-subunit associated with one or two auxiliary ?-subunits. These channels are classically known for being responsible of action potential generation and propagation in excitable cells; but lately they have been reported as widely expressed and regulated in several human cancer types. We have previously demonstrated the overexpression of NaV1.6 channel in cervical cancer (CeCa) biopsies and primary cultures, and its contribution to cell migration and invasiveness. Here, we investigated the expression of NaV channels ?-subunits (NaV?s) in the CeCa cell lines HeLa, SiHa and CaSki, and determined their contribution to cell proliferation, migration and invasiveness. Methods:We assessed the expression of NaV?s in CeCa cell lines by performing RT-PCR and western blotting experiments. We also evaluated CeCa cell lines proliferation, migration, and invasion by in vitro assays, both in basal conditions and after inducing changes in NaV?s levels by transfecting specific cDNAs or siRNAs. The potential role of NaV?s in modulating the expression of NaV ?-subunits in the plasma membrane of CeCa cells was examined by the patch-clamp whole-cell technique. Furthermore, we investigated the role of NaV?1 on cell cycle in SiHa cells by flow cytometry. Results:We found that the four NaV?s are expressed in the three CeCa cell lines, even in the absence of functional NaV ?-subunit expression in the plasma membrane. Functional in vitro assays showed differential roles for NaV?1 and NaV?4, the latter as a cell invasiveness repressor and the former as a migration abolisher in CeCa cells. In silico analysis of NaV?4 expression in cervical tissues corroborated the downregulation of this protein expression in CeCa vs normal cervix, supporting the evidence of NaV?4's role as a cell invasiveness repressor. Conclusions:Our results contribute to the recent conception about NaV?s as multifunctional proteins involved in cell processes like ion channel regulation, cell adhesion and motility, and even in metastatic cell behaviors. These non-canonical functions of NaV?s are independent of the presence of functional NaV ?-subunits in the plasma membrane and might represent a new therapeutic target for the treatment of cervical cancer.

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A voltage-gated sodium channel is essential for the positive selection of CD4(+) T cells.

Publications

A voltage-gated sodium channel is essential for the positive selection of CD4(+) T cells.

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