Swelling-activated taurine and K + transport in human cervical cancer cells: association with cell cycle progression

Abstract

The aim of this study was to investigate swelling-activated taurine and K+ transport in human cervical cancer cells under various culture conditions, testing the hypothesis that the progression of cell cycle was accompanied by differential activities of swelling-activated transport pathways. Aphidicolin, an inhibitor of deoxyribonucleic acid (DNA) synthesis, was used to synchronize the cell cycle. The distribution of cell cycle stage was determined by fluorescence-activated cell sorting (FACS). Hypotonicity activated taurine efflux, which was sensitive to tamoxifen and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB). Cell swelling also induced both Cl- -dependent and -independent K+ (86Rb+) efflux, presumably mediated by KCl cotransport (KCC) and Ca2+ -activated K+ channels, respectively. Cell cycle arrest in G0/G1 was accompanied by a remarkable decrease in the rate constant for swelling-activated taurine efflux, from 0.20+/-0.007 to 0.026+/-0.002 min(-1) (n=6). The activity of swelling-activated taurine efflux recovered progressively on re-entry into the cell cycle. After removal of aphidicolin and culture with 10% fetal calf serum for 10 h, the rate constant increased significantly from 0.026+/-0.002 to 0.093+/-0.002 min(-1) (n=6). After 24 h release from aphidicolin, the efflux rate constant had increased further to 0.195+/-0.006 min(-1) (n=6), a value not significantly different from that in normally proliferating cells. The differential activities of swelling-activated taurine transport matched well with our previous study showing a volume-sensitive anion channel associated with cell cycle progression. In contrast to the differential activities of swelling-activated taurine transport, swelling-activated K+ (86Rb+) transport was independent of the progression of cell cycle. Most importantly, pharmacological blockade of swelling-activated taurine efflux by tamoxifen or NPPB caused proliferating cervical cancer cells to arrest in G0/G1, suggesting that the activity of this efflux was associated with G1/S checkpoint progression. This study provides new and important information on the functional significance of swelling-activated transport system in the regulation of cell cycle clock of human cervical cancer cells.

Regulation of cell proliferation by intermediate-conductance Ca2+-activated potassium and volume-sensitive chloride channels in mouse mesenchymal stem cells

“…1-3) and accumulated cells at G 0 /G 1 phase (Fig. 5); this finding is consistent with recent observations in cancer cells and fibroblasts (6,34,45). Our results demonstrated that this effect is related to the downregulation of the cell cycle regulatory proteins cyclin D1 and cyclin E (Fig.…”

Effect of osmotic stress on the expression of TRPV4 and BKCa channels and possible interaction with ERK1/2 and p38 in cultured equine chondrocytes

“…Phosphorylation of p38 MAPK following hyperosmotic stress has been shown in several cell types, such as fibroblasts (23), human cervical cells (36), and human articular chondrocytes (41,42). In agreement with these studies, we have shown an elevation of p38 MAPK phosphorylation following hyperosmotic stress at early phases of the exposure.…”

“…The role of the ERK1/2 pathway in RVD has not been delineated; however, indirect activation of ERK1/2 via the Ras-Raf-MEK pathway has been suggested in hepatocytes (8). Other studies have linked activation of ERK1/2 to activation of the Cl Ϫ channel in corneal epithelial cells (19) and astrocytes (6) and to activation of the K ϩ channel in cervical cancer cells (36). Although Cl Ϫ and K ϩ play an important role in volume regulation following cell swelling in response to hypo-osmotic stress and elevation of intracellular Ca 2ϩ (18), the current study suggests a link between ERK1/2 phosphorylation and TRPV4 channel expression, where ERK1/2 phosphorylation regulates endogenous TRPV4 channel expression.…”

Swelling-Induced Taurine Transport: Relationship with Chloride Channels, Anion-Exchangers and Other Swelling-Activated Transport Pathways

“…[22,38,43,90,92,[101][102][103]. As discussed above, inhibition by either compound is commonly cited as evidence for taurine transport via volume-activated anion channels.…”