Disease relevance of AKT2

• We report here that the inward-rectifying potassium channels KAT1 and AKT2 were functionally expressed in K+ uptake-deficient Escherichia coli [1].

High impact information on AKT2

• 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 [2].
• 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 [2].
• The AKT2 mRNA level is upregulated by abscisic acid [2].
• The expression of AtPP2CA (beta-glucuronidase reporter gene) displayed a pattern largely overlapping that of AKT2 and was upregulated by abscisic acid [2].
• The Arabidopsis phloem channel AKT3 is the founder of a subfamily of shaker-like plant potassium channels characterized by weak rectification, Ca(2+) block, proton inhibition, and, as shown in this study, K(+) sensitivity [3].

Biological context of AKT2

• To confirm the akt2/3-1 phenotype, two independent knockout mutants, akt2-1 and akt2::En-1 were tested, demonstrating that the loss of AKT2/3 indeed affects the Ca2+ dependence of guard cell inward rectifier [4].
• All of the data are consistent with the hypothesis that the encoded polypeptide corresponds to the longest open reading frame previously identified (AKT2) [5].
• The molecular aspects of AKT2 regulation by phosphorylation, and the possible physiological meaning of such regulation in the plant context, are discussed [6].
• Gating mode 1 AKT2 channels behave as delayed K(+)-selective inward rectifiers; while gating mode 2 AKT2 channels are K(+)-selective 'open leaks' in the physiological range of membrane potential [6].
• Suppression of inward-rectifying K+ channels KAT1 and AKT2 by dominant negative point mutations in the KAT1 alpha-subunit [7].

Anatomical context of AKT2

• AKT2/3 subunits render guard cell K+ channels Ca2+ sensitive [4].
• Patch-clamp experiments with guard cell protoplasts from wild type and akt2/3-1 mutant, however, revealed pronounced differences in Ca2+ sensitivity of the K+ inward rectifier [4].
• In the present study we have investigated modulation of AKT2 current by effectors of phosphatases/kinases in COS cells and Xenopus oocytes [6].
• In apical root cells, AKT1 but not AKT2 contributed to the K+ permeability of the plasma membrane [8].

Associations of AKT2 with chemical compounds

• From our studies we thus conclude that AKT2/3 regulates the sucrose/H(+) symporters via the phloem potential [9].
• We conclude that the lysine residue K197 sensitizes AKT2 to phosphoregulation [10].
• Substitution of the lysine by serine or aspartate abolished the "open-lock" characteristic and converted AKT2 into an inward-rectifying channel [10].
• In leaves and flower stalk, the light-induced transcription of akt2/3 was suppressed by CO2-free air, indicating that gene activity is under the control of photosynthates [11].

Physical interactions of AKT2

• The AKT3 potassium channel protein interacts with the AtPP2CA protein phosphatase 2C [12].

Other interactions of AKT2

• Three members of the so-called Shaker K+ channel gene family (nine genes identified in Arabidopsis) play a role in these transports: AKT1, SKOR and AKT2 [13].
• Here we report the isolation of a novel Arabidopsis thaliana cDNA (AKT2) that is highly homologous to the two previously identified K+ channel genes, KAT1 and AKT1 [14].
• Homo- and heteromeric interactions between Arabidopsis K(+) channels KAT1, AKT1, and AKT2 were identified [15].
• In addition, we also detected transcripts for AtPP2CA, a protein phosphatase, that interacts with AKT2/3 [16].

Analytical, diagnostic and therapeutic context of AKT2

• Rapid amplification of cDNA ends with polymerase chain reaction and site-directed mutagenesis was performed to identify the initiation codon for AKT2 translation [5].
• By using the whole-mount and in situ hybridization techniques, we found AKT3 predominantly expressed in the phloem [17].
• To study the physiological role of this channel type, AKT3 was heterologously expressed in Xenopus oocytes, and the electrical properties were examined with voltage-clamp techniques [17].
• Northern blot analyses revealed the highest akt2/3-concentrations in the flower stalk, followed by the leaf, flower and stem [11].

References