Physical and functional interaction of the Arabidopsis K+ channel AKT2 and phosphatase AtPP2CA. Plant Cell

Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, Unité Mixte de Recherche 5004 Agro-M/Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique/Université Montpellier II, France.
The Plant Cell (Impact Factor: 9.34). 06/2002; 14(5):1133-46.
Source: PubMed


The AKT2 K(+) channel is endowed with unique functional properties, being the only weak inward rectifier characterized to date in Arabidopsis. The gene is expressed widely, mainly in the phloem but also at lower levels in leaf epiderm, mesophyll, and guard cells. The AKT2 mRNA level is upregulated by abscisic acid. By screening a two-hybrid cDNA library, we isolated a protein phosphatase 2C (AtPP2CA) involved in abscisic acid signaling as a putative partner of AKT2. We further confirmed the interaction by in vitro binding studies. The expression of AtPP2CA (beta-glucuronidase reporter gene) displayed a pattern largely overlapping that of AKT2 and was upregulated by abscisic acid. Coexpression of AtPP2CA with AKT2 in COS cells and Xenopus laevis oocytes was found to induce both an inhibition of the AKT2 current and an increase of the channel inward rectification. Site-directed mutagenesis and pharmacological analysis revealed that this functional interaction involves AtPP2CA phosphatase activity. Regulation of AKT2 activity by AtPP2CA in planta could allow the control of K(+) transport and membrane polarization during stress situations.

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Available from: Jean-Baptiste Thibaud, Jan 23, 2014
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    • "A de/phosphorylation network is thought to regulate the functional switch from influx to efflux, with AtPP2CA dephosphorylation found to repress the ability of AKT2 to move K ? out of the cell (Chérel et al. 2002; Sandmann et al. 2011). While AtCIPK6 has been shown not to phosphorylate AKT2, interaction of the AtCBL4–CIPK6 complex with AKT2 is necessary to activate AKT2's K ? "
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    • " and play important roles in K + homeostasis (Gaymard et al. 1998; Lebaudy et al. 2010; Marten et al. 1999; Pilot et al. 2001; Xicluna et al. 2007). ABA up-regulated the expression of AKT2 and decreased the expression of SKOR under drought and high salinity stresses (Deeken et al. 2002; Gaymard et al. 1998; Lacombe et al. 2000; Marten et al. 1999). Cherel et al. (2002) provided evidence that AtPP2CA, a protein phosphatase involved in ABA signaling, interacts with AKT2 and is considered a partner of AKT2. It was reported that SRK2E/OST1/SnRK2.6, one of the subclass β SnRK2 family members, global regulators of ABA signaling, inhibits the activity of KAT1, an inward K + channel, through phosphorylation o"
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    • "The various combinations of CBLs-CIPKs may be able to control diverse biological processes since Arabidopsis has ten CBL proteins (Kudla et al., 1999) and at least 25 CIPKs (Luan et al., 2009). More examples of complexities in the regulation of K+ channels are also provided by the interaction of K+ channels with PROTEIN PHOSPHATASE 2C (PP2C) (Cherel et al., 2002; Lan et al., 2011) and SNARE proteins (Honsbein et al., 2009). PP2Cs directly interact with the kinase domain of CIPK in the CBLCIPK complex and dephosphorylate CIPK, resulting in the inactivation of AKT1 (Cherel et al., 2002; Lan et al., 2011). "
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