Up-Regulation of Intestinal Phosphate Transporter NaPi-IIb (SLC34A2) by the Kinases SPAK and OSR1

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Abstract

Background/Aims: SPAK (SPS1-related proline/alanine-rich kinase) and OSR1 (oxidative stress-responsive kinase 1), kinases controlled by WNK (with-no-K[Lys] kinase), are powerful regulators of cellular ion transport and blood pressure. Observations in gene-targeted mice disclosed an impact of SPAK/OSR1 on phosphate metabolism. The present study thus tested whether SPAK and/or OSR1 contributes to the regulation of the intestinal Na+-coupled phosphate co-transporter NaPi-IIb (SLC34A2). Methods: cRNA encoding NaPi-IIb was injected into Xenopus laevis oocytes without or with additional injection of cRNA encoding wild-type SPAK, constitutively active T233ESPAK, WNK insensitive T233ASPAK, catalytically inactive D212ASPAK, wild-type OSR1, constitutively active T185EOSR1, WNK insensitive T185AOSR1 or catalytically inactive D164AOSR1. The phosphate (1 mM)-induced inward current (IPi) was taken as measure of phosphate transport. Results: IPi was observed in NaPi-IIb expressing oocytes but not in water injected oocytes, and was significantly increased by co-expression of SPAK, T233ESPAK, OSR1, T185EOSR1 or SPAK+OSR1, but not by co-expression of T233ASPAK, D212ASPAK, T185AOSR1, or D164AOSR1. SPAK and OSR1 both increased the maximal transport rate of the carrier. Conclusions: SPAK and OSR1 are powerful stimulators of the intestinal Na+-coupled phosphate co-transporter NaPi-IIb.

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Physiology of cell volume regulation in vertebrates.

Else K. Hoffmann, Ian H. Lambert, Stine F. Pedersen (2009)

The ability to control cell volume is pivotal for cell function. Cell volume perturbation elicits a wide array of signaling events, leading to protective (e.g., cytoskeletal rearrangement) and adaptive (e.g., altered expression of osmolyte transporters and heat shock proteins) measures and, in most cases, activation of volume regulatory osmolyte transport. After acute swelling, cell volume is regulated by the process of regulatory volume decrease (RVD), which involves the activation of KCl cotransport and of channels mediating K(+), Cl(-), and taurine efflux. Conversely, after acute shrinkage, cell volume is regulated by the process of regulatory volume increase (RVI), which is mediated primarily by Na(+)/H(+) exchange, Na(+)-K(+)-2Cl(-) cotransport, and Na(+) channels. Here, we review in detail the current knowledge regarding the molecular identity of these transport pathways and their regulation by, e.g., membrane deformation, ionic strength, Ca(2+), protein kinases and phosphatases, cytoskeletal elements, GTP binding proteins, lipid mediators, and reactive oxygen species, upon changes in cell volume. We also discuss the nature of the upstream elements in volume sensing in vertebrate organisms. Importantly, cell volume impacts on a wide array of physiological processes, including transepithelial transport; cell migration, proliferation, and death; and changes in cell volume function as specific signals regulating these processes. A discussion of this issue concludes the review.

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Human hypertension caused by mutations in WNK kinases.

F. Wilson, S Disse-Nicodème, K A Choate … (2001)

Hypertension is a major public health problem of largely unknown cause. Here, we identify two genes causing pseudohypoaldosteronism type II, a Mendelian trait featuring hypertension, increased renal salt reabsorption, and impaired K+ and H+ excretion. Both genes encode members of the WNK family of serine-threonine kinases. Disease-causing mutations in WNK1 are large intronic deletions that increase WNK1 expression. The mutations in WNK4 are missense, which cluster in a short, highly conserved segment of the encoded protein. Both proteins localize to the distal nephron, a kidney segment involved in salt, K+, and pH homeostasis. WNK1 is cytoplasmic, whereas WNK4 localizes to tight junctions. The WNK kinases and their associated signaling pathway(s) may offer new targets for the development of antihypertensive drugs.

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The WNK1 and WNK4 protein kinases that are mutated in Gordon's hypertension syndrome phosphorylate and activate SPAK and OSR1 protein kinases.

Dario Alessi, Maria Deak, Alberto C. Vitari … (2005)

Mutations in the human genes encoding WNK1 [with no K (lysine) protein kinase-1] and the related protein kinase WNK4 are the cause of Gordon's hypertension syndrome. Little is known about the molecular mechanism by which WNK isoforms regulate cellular processes. We immunoprecipitated WNK1 from extracts of rat testis and found that it was specifically associated with a protein kinase of the STE20 family termed 'STE20/SPS1-related proline/alanine-rich kinase' (SPAK). We demonstrated that WNK1 and WNK4 both interacted with SPAK as well as a closely related kinase, termed 'oxidative stress response kinase-1' (OSR1). Wildtype (wt) but not catalytically inactive WNK1 and WNK4 phosphorylated SPAK and OSR1 to a much greater extent than with other substrates utilized previously, such as myelin basic protein and claudin-4. Phosphorylation by WNK1 or WNK4 markedly increased SPAK and OSR1 activity. Phosphopeptide mapping studies demonstrated that WNK1 phosphorylated kinase-inactive SPAK and OSR1 at an equivalent residue located within the T-loop of the catalytic domain (Thr233 in SPAK, Thr185 in OSR1) and a serine residue located within a C-terminal non-catalytic region (Ser373 in SPAK, Ser325 in OSR1). Mutation of Thr185 to alanine prevented the activation of OSR1 by WNK1, whereas mutation of Thr185 to glutamic acid (to mimic phosphorylation) increased the basal activity of OSR1 over 20-fold and prevented further activation by WNK1. Mutation of Ser325 in OSR1 to alanine or glutamic acid did not affect the basal activity of OSR1 or its ability to be activated by WNK1. These findings suggest that WNK isoforms operate as protein kinases that activate SPAK and OSR1 by phosphorylating the T-loops of these enzymes, resulting in their activation. Our analysis also describes the first facile assay that can be employed to quantitatively assess WNK1 and WNK4 activity.

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Journal ID (publisher-id): KBR

Journal ID (nlm-ta): Kidney Blood Press Res

Journal ID (doi): 10.1159/issn.1420-4096

Title: Kidney and Blood Pressure Research

Publisher: S. Karger AG

ISSN (Print): 1420-4096

ISSN (Electronic): 1423-0143

Publication date Subscription-year: 2015

Publication date (Print): December 2015

Publication date (Electronic): 28 October 2015

Volume: 40

Issue: 6

Pages: 555-564

Affiliations

^aDepartment of Physiology I, University of Tübingen, Tübingen, Germany; ^bEnvironmental Biomonitoring Laboratory (LBE LR01/ES14), Faculty of Sciences of Bizerte, University of Carthage, Tunisia; ^cExperimental Retinal Prosthetics Group, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany

Author notes

*Prof. Dr. Florian Lang, Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076 Tübingen, (Germany), Tel. +49 7071/2972194, Fax +49 7071/295618, E-Mail florian.lang@uni-tuebingen.de

Article

Publisher ID: 368531 Other ID: Kidney Blood Press Res 2015;40:555-564

DOI: 10.1159/000368531

PubMed ID: 26506223

SO-VID: aa85d2cd-b13e-4b09-b377-d259e324928f

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Open Access License: This is an Open Access article licensed under the terms of the Creative Commons Attribution-NonCommercial 3.0 Unported license (CC BY-NC) ( http://www.karger.com/OA-license), applicable to the online version of the article only. Distribution permitted for non-commercial purposes only. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

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Up-Regulation of Intestinal Phosphate Transporter NaPi-IIb (SLC34A2) by the Kinases SPAK and OSR1

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Karger: Nephrology

Most cited references 64

Physiology of cell volume regulation in vertebrates.

Human hypertension caused by mutations in WNK kinases.

The WNK1 and WNK4 protein kinases that are mutated in Gordon's hypertension syndrome phosphorylate and activate SPAK and OSR1 protein kinases.

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