Expression of Transient Receptor Potential Vanilloid Channels TRPV5 and TRPV6 in Human Blood Lymphocytes and Jurkat Leukemia T Cells

Abstract

Regulation of Ca(2+) entry is a key process for lymphocyte activation, cytokine synthesis and proliferation. Several members of the transient receptor potential (TRP) channel family can contribute to changes in [Ca(2+)](in); however, the properties and expression levels of these channels in human lymphocytes continue to be elusive. Here, we established and compared the expression of the most Ca(2+)-selective members of the TRPs, Ca(2+) channels transient receptor potential vanilloid 5 and 6 (TRPV5 and TRPV6), in human blood lymphocytes (HBLs) and leukemia Jurkat T cells. We found that TRPV6 and TRPV5 mRNAs are expressed in both Jurkat cells and quiescent HBLs; however, the levels of mRNAs were significantly higher in malignant cells than in quiescent lymphocytes. Western blot analysis showed TRPV5/V6 proteins in Jurkat T cells and TRPV5 protein in quiescent HBLs. However, the expression of TRPV6 protein was switched off in quiescent HBLs and turned on after mitogen stimulation of the cells with phytohemagglutinin. Inwardly directed monovalent currents that displayed characteristics of TRPV5/V6 currents were recorded in both Jurkat cells and normal HBLs. In outside-out patch-clamp studies, currents were reduced by ruthenium red, a nonspecific inhibitor of TRPV5/V6 channels. In addition, ruthenium red downregulated cell-cycle progression in both activated HBLs and Jurkat cells. Thus, we identified TRPV5 and TRPV6 calcium channels, which can be considered new candidates for Ca(2+) entry into human lymphocytes. The correlation between expression of TRPV6 channels and the proliferative status of lymphocytes suggests that TRPV6 may be involved in the physiological and/or pathological proliferation of lymphocytes.

Functional expression of TRPV channels in T cells and their implications in immune regulation

“…In this work, we demonstrate that TRPV1, TRPV2, TRPV3 and TRPV4, all thermosensitive in nature, are endogenously expressed in Jurkat cells (human T cell line), primary T cells from human PBMCs and murine splenocytes. Our results are also in line with recent reports where it has been shown that functional TRPV5 and TRPV6 are expressed in T cells and that expression of these channels increases upon mitogenic activation. In this work, we show that TRPV1 and TRPV4 activation by specific ligands leads to Ca 2+ influx in purified murine T cells, indicating that these channels are present and functional even in resting T cells.…”

TRPV5/V6 Channels Mediate Ca2+ Influx in Jurkat T Cells Under the Control of Extracellular pH

“…Voltage‐current relations obtained from unitary currents recorded at different voltages displayed typical for calcium channels TRPV5/V6 inward rectification and a single channel conductance of 38 pS. The endogenous expression of TRPV5/V6 were confirmed by real‐time PCR and Western blot analysis [Vassilieva et al, ]. Here, we investigated the mechanisms of regulation of TRPV5/V6 channels in Jurkat T cells.…”

“…Earlier, in patch–clamp experiments on human blood lymphocytes (HBLs) and Jurkat T cell [Vassilieva et al, ], we showed the sensitivity of TRPV5/V6 channels in these cells to ruthenium red, a widely used, although not completely selective, inhibitor of TRPV5 and TRPV6 channels [Hoenderop et al, ; Schoeber et al, ]. In order to test if TRPV5/V6 channels mediate the Ca 2+ influx in these cells, ruthenium red was used in Ca 2+ measurements.…”

Transient Receptor Potential (TRP) channels in T cells

“…The functional expression of the Ca 2+ -selective TRPV5 and TRPV6 channels was reported in mouse and human primary T cells and in Jurkat cells [15, 50, 51]. However, Trpv6 -/- mice have no reported immunological phenotype [52] and TCR-induced Ca 2+ influx in CD4 + T cells from Trpv6 -/- mice is normal [53].…”

“…However, the role of TRPV6 as a CRAC channel could not be established [54, 55] as BTP2 (a pyrazole derivative and CRAC channel inhibitor) did not affect the activity of the TRPV6 channel [56]. Recently, it was reported that both TRPV5 and TRPV6 are involved in Ca 2+ entry and cell cycle progression of human primary T cells and Jurkat cells [50]. The activity of these two channels in Jurkat cells was also shown to be modulated by extracellular pH [57].…”