| Autor: |
Stevanović KS; Faculty of Biology, Institute of Physiology and Biochemistry, University of Belgrade, Studentski Trg 16, 11158 Belgrade, Serbia., Čepkenović B; Faculty of Biology, Institute of Physiology and Biochemistry, University of Belgrade, Studentski Trg 16, 11158 Belgrade, Serbia., Križak S; Institute of Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade, Serbia., Živić MŽ; Faculty of Biology, Institute of Physiology and Biochemistry, University of Belgrade, Studentski Trg 16, 11158 Belgrade, Serbia., Todorović NV; Institute of Biological Research 'Siniša Stanković', National Institute of the Republic of Serbia, University of Belgrade, Bulevar Despota Stefana 142, 11000 Belgrade, Serbia. |
| Abstrakt: |
Studies of ion currents in filamentous fungi are a prerequisite for forming a complete understanding of their physiology. Cytoplasmic droplets (CDs), obtained from sporangiophores of Phycomyces blakesleeanus, are a model system that enables the characterization of ion currents in the native membrane, including the currents mediated by the channels not yet molecularly identified. Osmotically activated anionic current with outward rectification (ORIC) is a dominant current in the membrane of cytoplasmic droplets under the conditions of hypoosmotic stimulation. We have previously reported remarkable functional similarities of ORIC with the vertebrate volume regulated anionic current (VRAC), such as dose-dependent activation by osmotic difference, ion selectivity sequence, and time and voltage dependent profile of the current. Using the patch clamp method on the CD membrane, we further resolve VRAC-like ORIC characteristics in this paper. We examine the inhibition by extracellular ATP and carbenoxolone, the permeation of glutamate in presence of chloride, selectivity for nitrates, and activation by GTP, and we show its single channel behavior in excised membrane. We propose that ORIC is a functional counterpart of vertebrate VRAC in filamentous fungi, possibly with a similar essential role in anion efflux during cell volume regulation. |
