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10th International Congress "Cell Volume Regulation: Novel Therapeutic Targets and Pharmacological Approaches"
VOLUME-SENSITIVE OUTWARDLY RECTIFYING ANION CHANNELS IN THE DEVELOPING BRAIN
Akita, T.
Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan
The volume-sensitive outwardly rectifying (VSOR) anion channel plays a major role in transporting anions across the cell membrane during cell volume regulation. The channel is typically activated by cell swelling in most types of animal cells, thereby facilitating a regulatory volume decrease process and also mediating intercellular communications through release of excitatory amino acids, like glutamate. The channel may also be activated without swelling when certain types of intracellular signaling cascades are elicited by some receptor stimulation. We previously demonstrated that opening of Ca2+-permeable ion channels triggered by Gq protein-coupled receptor activation elicits VSOR channel activation through high concentration regions of intracellular Ca2+ in the immediate vicinity of Ca2+ channels, so called "Ca2+ nanodomains" [1, 2]. This mechanism would provide a basis for local control of cell volume regulation associated with cell shape
changes during cell proliferation, differentiation and migration. The roles of the VSOR channel in regulatory and apoptotic volume decreases had been extensively studied so far, especially in tumor cells. But its roles in cell proliferation, differentiation and migration, especially in the neurons in the developing brain, have not been elucidated yet. I have recently begun to examine the VSOR channel in the developing brain, and I would like to report my recent attempts to elucidate the roles of the channel, especially in the context of providing driving forces for cell migration and of communications between neurons during the developing process.
References
1. Akita, T. and Okada, Y. J. Physiol. (London), 2011, 589 (16), pp. 3909-3927.
2. Akita, T., Fedorovich, S.V., and Okada, Y. Cell Physiol. Biochem, 2011, 28, pp. 1181-1190.
NA+ IMPORT IS THE RATE-LIMITING STEP OF CELL RE-HYDRATION AFTER CRYO-PRESERVATION
Azer, L., Christmann, J., Bastiaens, P.I.H., and Wehner, F.
Max Planck Institute of Molecular Physiology, Department of Systemic Cell Biology, Dortmund, Germany
During cryo-preservation, cells loose considerable amounts of water and they partial regain volumes when brought back from the cold. Here we applied different levels of hypertonic stress as well as cryo-conditions (-50 °C) to perturb the hydration (volume) of HepG2 cells and to define the activation energies (Eas) of aquaporins (AQPs) and HICCs using scanning acoustic microscopy and whole-cell patch-clamp recordings. The Eas of regulatory volume increase (RVI) and HICCs
showed a defined osmotic profile, whereas activation of AQPs did not depend on hypertonicity. The Eas of RVI were significantly decreased after cryo-preservation indicative of a higher capability of cells to regain osmolytes and water, very likely through a stimulation of cation uptake. In sharp contrast, the Eas of AQPs were not significantly changed after cryo-preservation, implying a rather permissive role of water channels in the process.
Бюллетень сибирской медицины, 2013, том 12, № 4, с. 24-68
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