Osmotic swelling activates a novel anionic current with VRAC-like properties in a cytoplasmic droplet membrane from Phycomyces blakesleeanus sporangiophores

ATP modulation of osmotically activated anionic current in the membrane of Phycomyces blakesleeanus sporangiophore

“…Yet, very little is known about the physiological mechanisms mediating their adaptability at the level of the cell membrane. Scarcity of studies addressing fungal membrane physiology is likely a direct consequence of experimental difficulties for electrophysiological measurements of ion currents 1 , rather than a lack of interest, since ecological 2 – 4 , biotechnological 5 , 6 and biomedical 7 – 10 significance of fungal physiology is undisputed.…”

“…Cytoplasmic droplets obtained from Phycomyces blakesleeanus sporangiophores have been used as an experimental model by our research group, for high-quality patch clamp measurements on a native fungal plasma membrane 1 , 11 . P. blakesleeanus is a saprophytic filamentous fungus from the order Mucorales, and can be considered as a proxy model system for the basic physiology of its medically and economically important cousins from the order Mucorales 12 – 14 .…”

“…Cytoplasmic droplets (CDs) are obtained from P. blakesleeanus sporangiophore, through spontaneous formation upon releasing the content from the tip of the sporangiophore in an adequate solution, as first described by Zaichkin et al 17 . Cytoplasmic droplets obtained this way are membrane-bound and have the potential to regenerate the cell wall 1 , 17 .…”

“…An outwardly rectifying, instantaneous, fast-inactivating current (ORIC) is a dominant current in the cytoplasmic droplet membrane under hypoosmotic conditions 1 . It shares some of the key features that define the biophysical signature of the vertebrate volume-regulated anion channel (VRAC): osmotic activation, mild outward rectification, selectivity for anions following Eisenman I series and inactivation at depolarizing potentials that resemble many of the VRAC isoforms 18 .…”

“…It shares some of the key features that define the biophysical signature of the vertebrate volume-regulated anion channel (VRAC): osmotic activation, mild outward rectification, selectivity for anions following Eisenman I series and inactivation at depolarizing potentials that resemble many of the VRAC isoforms 18 . One of the most striking features of ORIC is the fast rundown accompanied with an increase in the speed of its inactivation 1 . Notably, all of these properties were discerned under the conditions of dialysis of the cytoplasmic droplet by patch pipette solution that lacked ATP.…”