Slow vacuolar channels from barley mesophyll cells are regulated by 14-3-3 proteins.
The conductance of the vacuolar membrane at elevated cytosolic Ca(2+) levels is dominated by the slow activating cation selective (SV) channel. At physiological, submicromolar Ca(2+) concentrations the SV currents are very small. Only recently has the role of 14-3-3 proteins in the regulation of voltage-gated and Ca(2+)-activated plasma membrane ion channels been investigated in Drosophila, Xenopus and plants. Here we report the first evidence that plant 14-3-3 proteins are involved in the down-regulation of ion channels in the vacuolar membrane as well. Using the patch-clamp technique we have demonstrated that 14-3-3 protein drastically reduces the current carried by SV channels. The current decline amounted to 80% and half-maximal reduction was reached within 5 s after 14-3-3-addition to the bath. The voltage sensitivity of the channel was not affected by 14-3-3. A coordinating role for 14-3-3 proteins in the regulation of plasma membrane and tonoplast ion transporters is discussed.
van den Wijngaard
P W
PW
BioCentrum Amsterdam, Department of Developmental Genetics, Faculty of Biology, Vrije Universiteit, Amsterdam, The Netherlands.
Bunney
T D
TD
Roobeek
I
I
Schönknecht
G
G
de Boer
A H
AH
D048948:14-3-3 Proteins; D002118:Calcium / Q000494:pharmacology; D004553:Electric Conductivity; D001467:Hordeum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D018408:Patch-Clamp Techniques; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*; D014617:Vacuoles / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*
D048948:14-3-3 Proteins; D007473:Ion Channels; D011993:Recombinant Fusion Proteins; D014446:Tyrosine 3-Monooxygenase; D002118:Calcium