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10th International Congress "Cell Volume Regulation: Novel Therapeutic Targets and Pharmacological Approaches"
ION CHANNELS INVOLVED IN CELL VOLUME REGULATION: ACTIVATION AND PHYSIOLOGICAL ROLES
Hoffmann, E.K.
Department of Biology, University of Copenhagen, Copenhagen, Denmark
Channels involved in regulation of cell volume in EATC and ELA are the K+ channel TASK-2, the volume regulated anion channel (VRAC) and the Ca2+ activated Cl- channels ANO1 and ANO6. TASK-2: Activation of TASK-2 by short term hypotonicity requires a tyrosine phosphorylation of the channel, long term hypotonicity results in a decreased TASK-2 current and a downregulation of TASK-2. TASK-2 is up-regulated in activated T-cells, and we investigate the functional role of TASK-2 in this activation. VRAC: The role of VRAC and other Cl- channels in apoptotic volume decrease (AVD), cell proliferation and migration was studied, and it was investigated if changes in the expression of Cl- channels are involved in chemotherapy resistance. In an attempt to find the molecular identity of VRAC, we cloned and expressed members of the ANO family of Cl- channels and investigated their role in cell volume regulation. Studies on ANO knock-downs shows that ANO6 plays a role in cell volume regulation, which is however secondary to a Ca2+ influx, in contrast to what is found for VRAC. We
investigated the role of the ANO Cl- channels in cell migration in ELA cells and found that ANO1 and ANO6 knock-down affect the directional migration and the rate of cell migration, respectively. ANO6 is also involved in apoptosis, possibly by contributing to AVD. Moreover we have explored AVD in wild type (wt) and Multidrug Resistant (MDR) EATC. Cisplatin leads to AVD and apopto-sis in wt EATC not in MDR cells, and the maximal capacity of VRAC is strongly repressed in MDR EATC. A VRAC inhibitor NS3728 abolishes the differences in AVD and caspase-3 activation between wt and MDR EATC suggesting that impairment of AVD via down regulation of VRAC protects against apoptosis in MDR EATC [1]. We are now comparing the expression of Cl-channels in wt and MDR EATC as well as in four pancreatic cancer cell lines and a normal pancreatic cell line (HPDE).
References
1. Poulsen, K.A., et al. 2010. Am. J. Physiol., 298, C14-C25.
GLYCINE FACILITATES PHAGOCYTOSIS BY A GLYCINE RECEPTOR-INDEPENDENT MECHANISM
Harl, B.1, Beyreis, M.2, Jakab, M.2, Ritter, M.2, and Kerschbaum, H.H.1
1 Department of Cell Biology, University of Salzburg, Salzburg, Austria
2 Institute of Physiology and Pathophysiology, Paracelsus Medical University, Salzburg, Austria
Glycine is involved in cell volume- as well as membrane-potential regulation. Cell shrinkage promotes an intra-cellular accumulation of glycine, which increases intracellu-lar osmotic pressure and, accordingly, influx of water until normal cell size is regained. Furthermore, binding of glycine to the glycine receptor increases a chloride conductance, whereas activation of system A neutral amino acid transporters (NAATs) increases a Na+ conductance. Both ions also contribute to cellular volume regulation. In a previous study, we proposed that phagocytosis may be explained by local volume regulatory mechanisms. Specifically, we suggest that formation of engulfment pseudopodia depends on localized perturbation in osmolarity. In the present study we evaluated the impact of glycine on polystyrene microsphere
uptake using the murine microglial cell line, BV-2. Glycine facilitated phagocytosis. Because this effect was neither suppressed by the glycine receptor antagonist strychnine, nor mimicked by the glycine receptor agonist taurine, glycine modulated phagocytosis in a glycine receptor (GlyR)-independent manner. Furthermore, mRNA of the glycine receptors GlyR1, GlyR2, GlyR3 or GlyR4 were not detected in BV-2 cells using PCR. However a-(methylamino) isobutyric acid (MeAIB), a specific substrate of NAATs, suppressed glycine-induced increase in phagocytosis. In line with this finding, substitution of Na+ with choline decreased uptake of microspheres. PCR revealed that BV-2 cell expressed the amino acid transporter Slc38a1, whereas Slc38a2 and Slc38a3 were not detected. Therefore, our find-
Бюллетень сибирской медицины, 2013, том 12, № 4, с. 24-68
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