Slow vacuolar channels from barley mesophyll cells are regulated by 14‐3‐3 proteins

Wijngaard, P.W.J. van den; Bunney, Tom D.; Roobeek, Ilja; Schönknecht, Gerald; Boer, Albertus H. de

doi:10.1016/s0014-5793(00)02394-2

Cited by 58 publications

(29 citation statements)

References 35 publications

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“…(Maathuis and Prins 1991b;Gambale et al 1993;Schulz-Lessdorf and Hedrich 1995;Carpaneto et al 2001). Measurements at low vacuolar Ca 2+ and over a wider potential range van den Wijngaard et al 2000) result in lower values for the gating charge.…”

Section: Divalent Cations and The Conductance Of Single Sv Channelsmentioning

confidence: 98%

“…In the literature quite different values, ranging from 1 to 3.8, have been reported for the gating charge of SV channels from different preparations (Maathuis and Prins 1991a;Gambale et al 1993;Reifarth et al 1994;Schulz-Lessdorf and Hedrich 1995;Pottosin et al 1997;van den Wijngaard et al 2000;Carpaneto et al 2001). Rather than reflecting actual differences between SV channels from different tissues, this seems to be caused Values of the parameters V 1 (midpoint potential for the transition between closed state C1 and open state O) and V 2 (midpoint potential for the transition between closed states C2 and C1) were obtained by fitting the data presented in Fig.…”

Section: Divalent Cations and The Conductance Of Single Sv Channelsmentioning

confidence: 99%

“…The SV channel is known to be regulated by Ca 2+ (Hedrich and Neher 1987;Ward and Schroeder 1994;Reifarth et al 1994), Mg 2+ (Pei et al 1999;Carpaneto et al 2001), calmodulin (Weiser et al 1991;Bethke and Jones 1994), kinases and phosphatases (Allen and Sanders 1995;Bethke and Jones 1997), pH (SchulzLessdorf and Hedrich 1995), redox agents (Carpaneto et al 1999), and 14-3-3 proteins (van den Wijngaard et al 2000). In addition, different factors, such divalent cations (Pottosin et al 2001), polyamines (Dobrovinskaya et al 1999a(Dobrovinskaya et al , 1999b, and heavy metals (Paganetto et al 2001;Carpaneto 2003), control the ion flux through the open channel.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism of luminal Ca2+ and Mg2+ action on the vacuolar slowly activating channels

Pottosin

Martínez‐Estévez

Dobrovinskaya

et al. 2004

Planta

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The non-selective slow vacuolar (SV) channel can dominate tonoplast conductance, making it necessary to tightly control its activity. Applying the patch-clamp technique to vacuoles from sugar beet (Beta vulgaris L.) taproots we studied the effect of divalent cations on the vacuolar side of the SV channel. Our results show that the SV channel has two independent binding sites for vacuolar divalent cations, (i) a less selective one, inside the channel pore, binding to which impedes channel conductance, and (ii) a Ca(2+)-selective one outside the membrane-spanning part of the channel protein, binding to which stabilizes the channel's closed conformations. Vacuolar Ca2+ and Mg2+ almost indiscriminately blocked ion fluxes through the open channel pore, decreasing measured single-channel current amplitudes. This low-affinity block displays marked voltage dependence, characteristic of a 'permeable blocker'. Vacuolar Ca(2+)-with a much higher affinity than Mg(2+)-slows down SV channel activation and shifts the voltage dependence to more (cytosol) positive potentials. A quantitative analysis results in a model that exactly describes the Ca(2+)-specific effects on the SV channel activation kinetics and voltage gating. According to this model, multiple (approximately three) divalent cations bind with a high affinity at the luminal interface of the membrane to the channel protein, favoring the occupancy of one of the SV channel's closed states (C2). Transition to another closed state (C1) diminishes the effective number of bound cations, probably due to mutual repulsion, and channel opening is accompanied by a decrease of binding affinity. Hence, the open state (O) is destabilized with respect to the two closed states, C1 and C2, in the presence of Ca2+ at the vacuolar side. The specificity for Ca2+ compared to Mg2+ is explained in terms of different binding affinities for these cations. In this study we demonstrate that vacuolar Ca2+ is a crucial regulator to restrict SV channel activity to a physiologically meaningful range, which is less than 0.1% of maximum SV channel activity.

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Section: Divalent Cations and The Conductance Of Single Sv Channelsmentioning

confidence: 98%

Section: Divalent Cations and The Conductance Of Single Sv Channelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mechanism of luminal Ca2+ and Mg2+ action on the vacuolar slowly activating channels

Pottosin

Martínez‐Estévez

Dobrovinskaya

et al. 2004

Planta

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“…Indeed, 14-3-3 proteins have been shown to downregulate currents of vacuolar SV channels by using whole-vacuole recordings (van den Wijngaard et al, 2001). Interestingly, docking of 14-3-3 proteins to the plasma membrane H ϩ -ATPase is induced by phosphorylation (Baunsgaard et al, 1998), which is so far not known to be essential for binding of proteins to TPR domains.…”

Section: Twd1 Functionally Interacts With Vacuolar Abc Transportersmentioning

confidence: 99%

ArabidopsisImmunophilin-like TWD1 Functionally Interacts with Vacuolar ABC Transporters

Geisler

Girin

Brandt

et al. 2004

MBoC

114

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Previously, the immunophilin-like protein TWD1 from Arabidopsis has been demonstrated to interact with the ABC transporters AtPGP1 and its closest homologue, AtPGP19. Physiological and biochemical investigation of pgp1/pgp19 and of twd1 plants suggested a regulatory role of TWD1 on AtPGP1/AtPGP19 transport activities. To further understand the dramatic pleiotropic phenotype that is caused by loss-of-function mutation of the TWD1 gene, we were interested in other TWD1 interacting proteins. AtMRP1, a multidrug resistance-associated (MRP/ABCC)-like ABC transporter, has been isolated in a yeast two-hybrid screen. We demonstrate molecular interaction between TWD1 and ABC transporters AtMRP1 and its closest homologue, AtMRP2. Unlike AtPGP1, AtMRP1 binds to the C-terminal tetratricopeptide repeat domain of TWD1, which is well known to mediate protein-protein interactions. Domain mapping proved that TWD1 binds to a motif of AtMRP1 that resembles calmodulin-binding motifs; and calmodulin binding to the C-terminus of MRP1 was verified. By membrane fractionation and GFP-tagging, we localized AtMRP1 to the central vacuolar membrane and the TWD1-AtMRP1 complex was verified in vivo by coimmunoprecipitation. We were able to demonstrate that TWD1 binds to isolated vacuoles and has a significant impact on the uptake of metolachlor-GS and estradiol-␤-glucuronide, well-known substrates of vacuolar transporters AtMRP1 and AtMRP2.

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“…Recently, increasing evidence suggests that besides the H ϩ -ATPase 14-3-3s can also regulate K ϩ channels. In fact, they have been shown to interact with plant K ϩ outward rectifiers (18 -20), SV channels (21), and K ϩ inward rectifiers (20). The effect of 14-3-3 proteins on K ϩ inward rectifiers has so far only been reported for native channels.…”

Section: -3-3 Proteins Modulate the Plant Inward Rectifier Kmentioning

confidence: 99%

The Potassium Channel KAT1 Is Activated by Plant and Animal 14-3-3 Proteins

Sottocornola

Visconti

Orsi

et al. 2006

Journal of Biological Chemistry

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14-3-3 proteins modulate the plant inward rectifier K؉ channel KAT1 heterologously expressed in Xenopus oocytes. Injection of recombinant plant 14-3-3 proteins into oocytes shifted the activation curve of KAT1 by ؉11 mV and increased the on . KAT1 was also modulated by 14-3-3 proteins of Xenopus oocytes. Titration of the endogenous 14-3-3 proteins by injection of the peptide Raf 621p resulted in a strong decrease in KAT1 current (ϳ70% at ؊150 mV). The mutation K56E performed on plant protein 14-3-3 in a highly conserved recognition site prevented channel activation. Because the maximal conductance of KAT1 was unaffected by 14-3-3, we can exclude that they act by increasing the number of channels, thus ruling out any effect of these proteins on channel trafficking and/or insertion into the oocyte membrane. 14-3-3 proteins also increased KAT1 current in inside-out patches, suggesting a direct interaction with the channel. Direct interaction was confirmed by overlay experiments with radioactive 14-3-3 on oocyte membranes expressing KAT1.

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Slow vacuolar channels from barley mesophyll cells are regulated by 14‐3‐3 proteins

Cited by 58 publications

References 35 publications

Mechanism of luminal Ca2+ and Mg2+ action on the vacuolar slowly activating channels

Mechanism of luminal Ca2+ and Mg2+ action on the vacuolar slowly activating channels

ArabidopsisImmunophilin-like TWD1 Functionally Interacts with Vacuolar ABC Transporters

The Potassium Channel KAT1 Is Activated by Plant and Animal 14-3-3 Proteins

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