Upregulation of Na+,Cl--Coupled Betaine/ γ-Amino-Butyric Acid Transporter BGT1 by Tau Tubulin Kinase 2

Almilaji, Ahmad; Muñoz, Carlos; Hosseinzadeh, Zohreh; Läng, Florian

doi:10.1159/000354441

Cited by 43 publications

(33 citation statements)

References 90 publications

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“…The voltage clamp experiments were performed at room temperature 3 days after injection. Two-electrode voltage-clamp recordings [45] were obtained utilizing a pulse protocol of 10 s pulses from -140 mV to +40 mV in 20 mV increments. The intermediate holding voltage was -60 mV.…”

Section: Methodsmentioning

confidence: 99%

Regulation of ClC-2 Activity by SPAK and OSR1

Warsi¹,

Hosseinzadeh²,

Elvira³

et al. 2014

Kidney Blood Press Res

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Background/Aims: SPAK (SPS1-related proline/alanine-rich kinase) and OSR1 (oxidative stress-responsive kinase 1) are powerful regulators of diverse transport processes. Both kinases are activated by cell shrinkage and participate in stimulation of regulatory cell volume increase (RVI). Execution of RVI involves inhibition of Cl^- channels. The present study explored whether SPAK and/or OSR1 regulate the activity of the Cl^- channel ClC-2. Methods: To this end, ClC-2 was expressed in Xenopus laevis oocytes with or without additional expression of wild type SPAK, constitutively active SPAK^T233E, WNK1 insensitive inactive SPAK^T233A, catalytically inactive SPAK^D212A, wild type OSR1, constitutively active OSR1^T185E, WNK1 insensitive inactive OSR1^T185A, and catalytically inactive OSR1^D164A. Cl^- channel activity was determined by dual electrode voltage clamp. Results: Expression of ClC-2 was followed by the appearance of a conductance (G_Cl), which was significantly decreased following coexpression of wild-type SPAK, SPAK^T233E, wild type OSR1 or OSR1^T185E, but not by coexpression of SPAK^T233A, SPAK^D212A, OSR1^T185A, or OSR1^D164A. Inhibition of ClC-2 insertion by brefeldin A (5 μM) resulted in a decline of G_Cl which was similar in the absence and presence of SPAK or OSR1, suggesting that SPAK and OSR1 did not accelerate the retrieval of ClC-2 protein from the cell membrane. Conclusion: SPAK and OSR1 are powerful negative regulators of the cell volume regulatory Cl^- channel ClC-2.

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Section: Methodsmentioning

confidence: 99%

Regulation of ClC-2 Activity by SPAK and OSR1

Warsi¹,

Hosseinzadeh²,

Elvira³

et al. 2014

Kidney Blood Press Res

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“…cRNA encoding K ir 2.1 (10 ng) was injected with or without 1, 3 or 10 ng of cRNA encoding either wild type human SGK3, constitutively active S419D SGK3 or inactive K191N SGK3 on the day of preparation of the Xenopus oocytes [47]. All experiments were performed at room temperature 3 days after injection.…”

Section: Methodsmentioning

confidence: 99%

Up-Regulation of K_ir2.1 (KCNJ2) by the Serum & Glucocorticoid Inducible SGK3

Muñoz

Pakladok²,

Almilaji³

et al. 2014

Cell Physiol Biochem

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Background/Aims: The serum & glucocorticoid inducible kinase SGK3, an ubiquitously expressed serine/threonine kinase, regulates a variety of ion channels. It has previously been shown that SGK3 upregulates the outwardly rectifying K⁺ channel K_V11.1, which is expressed in cardiomyocytes. Cardiomyocytes further express the inward rectifier K⁺ channel K_ir2.1, which contributes to maintenance of resting cell membrane potential. Loss-of-function mutations of KCNJ2 encoding K_ir2.1 result in Andersen-Tawil syndrome with periodic paralysis, cardiac arrhythmia and dysmorphic features. The present study explored whether SGK3 participates in the regulation of K_ir2.1. Methods: cRNA encoding K_ir2.1 was injected into Xenopus oocytes with and without additional injection of cRNA encoding wild type SGK3, constitutively active ^S419DSGK3 or inactive ^K191NSGK3. K_ir2.1 activity was determined by two-electrode voltage-clamp and K_ir2.1 protein abundance in the cell membrane by immunostaining and subsequent confocal imaging or by chemiluminescence. Results: Injection of 10 ng cRNA encoding wild type SGK3 and ^S419DSGK3, but not ^K191NSGK3 significantly enhanced K_ir2.1-mediated currents. SGK inhibitor EMD638683 (50 µM) abrogated ^S419DSGK3-induced up-regulation of K_ir2.1. Moreover, wild type SGK3 enhanced the channel protein abundance in the cell membrane. The decay of K_ir2.1-mediated currents following inhibition of channel insertion into the cell membrane by brefeldin A (5 µM) was similar in oocytes coexpressing K_ir2.1 and SGK3 as in oocytes expressing K_ir2.1 alone, suggesting that SGK3 influences channel insertion into rather than channel retrieval from the cell membrane. Conclusions: SGK3 is a novel regulator of K_ir2.1.

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“…Constructs encoding human wild-type Kir2.1 (KCNJ2) [60] OSR1/pGHJ [62], were used for generation of cRNA as described previously [63,64]. The constructs were a kind gift from Dario Alessi (University of Dundee).…”

Section: Constructsmentioning

confidence: 99%