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  • 1
    Online Resource
    Online Resource
    Regulation of the renal-specific Na+–K+–2Cl− co-transporter NKCC2 by AMP-activated protein kinase (AMPK)
    Portland Press Ltd. ; 2007
    In:  Biochemical Journal Vol. 405, No. 1 ( 2007-07-01), p. 85-93
    Details
    In: Biochemical Journal, Portland Press Ltd., Vol. 405, No. 1 ( 2007-07-01), p. 85-93
    Abstract: The renal-specific NKCC2 (Na+–K+–2Cl− co-transporter 2) is regulated by changes in phosphorylation state, however, the phosphorylation sites and kinases responsible have not been fully elucidated. In the present study, we demonstrate that the metabolic sensing kinase AMPK (AMP-activated protein kinase) phosphorylates NKCC2 on Ser126in vitro. Co-precipitation experiments indicated that there is a physical association between AMPK and the N-terminal cytoplasmic domain of NKCC2. Activation of AMPK in the MMDD1 (mouse macula densa-derived 1) cell line resulted in an increase in Ser126 phosphorylation in situ, suggesting that AMPK may phosphorylate NKCC2 in vivo. The functional significance of Ser126 phosphorylation was examined by mutating the serine residue to an alanine residue resulting in a marked reduction in co-transporter activity when exogenously expressed in Xenopus laevis oocytes under isotonic conditions. Under hypertonic conditions no significant change of activity was observed. Therefore the present study identifies a novel phosphorylation site that maintains NKCC2-mediated transport under isotonic or basal conditions. Moreover, the metabolic-sensing kinase, AMPK, is able to phosphorylate this site, potentially linking the cellular energy state with changes in co-transporter activity.
    Type of Medium: Online Resource
    ISSN: 0264-6021 , 1470-8728
    URL: Article
    DOI: 10.1042/BJ20061850
    RVK:
    WA 15000
    Language: English
    Publisher: Portland Press Ltd.
    Publication Date: 2007
    detail.hit.zdb_id: 1473095-9
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  • 2
    Online Resource
    Online Resource
    Identification of a Parathyroid Hormone in the Fish Fugu rubripes
    Wiley ; 2003
    In:  Journal of Bone and Mineral Research Vol. 18, No. 7 ( 2003-07-01), p. 1326-1331
    Details
    In: Journal of Bone and Mineral Research, Wiley, Vol. 18, No. 7 ( 2003-07-01), p. 1326-1331
    Type of Medium: Online Resource
    ISSN: 0884-0431
    URL: Article
    DOI: 10.1359/jbmr.2003.18.7.1326
    RVK:
    XA 52230
    Language: English
    Publisher: Wiley
    Publication Date: 2003
    detail.hit.zdb_id: 2008867-X
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  • 3
    Online Resource
    Online Resource
    Regulation of the energy sensor AMP-activated protein kinase in the kidney by dietary salt intake and osmolality
    American Physiological Society ; 2005
    In:  American Journal of Physiology-Renal Physiology Vol. 288, No. 3 ( 2005-03), p. F578-F586
    Details
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 288, No. 3 ( 2005-03), p. F578-F586
    Abstract: The AMP-activated protein kinase (AMPK) is a key controller of cellular energy metabolism. We studied its expression and regulation by salt handling in the kidney. Immunoprecipitation and Western blots of protein lysates from whole rat kidney using subunit-specific antibodies showed that the α 1 -catalytic subunit is expressed in the kidney, associated with the β 2 - and either γ 1 - or γ 2 -subunits. Activated AMPK, detected by immunohistochemical staining for phospho-Thr 172 AMPK (pThr 172 ), was expressed on the apical surface of the cortical thick ascending limb of the loop of Henle, including the macula densa, and some parts of the distal convoluted tubule. Activated AMPK was also expressed on the basolateral surface of the cortical and medullary collecting ducts as well as some portions of the distal convoluted tubules. AMPK activity was increased by 25% in animals receiving a high-salt diet, and this was confirmed by Western blotting for pThr 172 . Low-salt diets were associated with reduced levels of the α-subunit of AMPK, which was highly phosphorylated on Thr 172 . Surprisingly, both low- and high-salt media transiently activated AMPK in the macula densa cell line MMDD1, an effect due to changes in osmolality, rather than Na + or Cl − concentration. This study, therefore, demonstrates regulation of AMPK by both a high- and a low-salt intake in vivo and suggests a role for the kinase in the response to changes in osmolality within the kidney.
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    URL: Article
    DOI: 10.1152/ajprenal.00190.2004
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2005
    detail.hit.zdb_id: 1477287-5
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  • 4
    Online Resource
    Online Resource
    Isoform-specific Purification and Substrate Specificity of the 5′-AMP-activated Protein Kinase
    Elsevier BV ; 1996
    In:  Journal of Biological Chemistry Vol. 271, No. 45 ( 1996-11), p. 28445-28450
    Details
    In: Journal of Biological Chemistry, Elsevier BV, Vol. 271, No. 45 ( 1996-11), p. 28445-28450
    Type of Medium: Online Resource
    ISSN: 0021-9258
    URL: Article
    DOI: 10.1074/jbc.271.45.28445
    Language: English
    Publisher: Elsevier BV
    Publication Date: 1996
    detail.hit.zdb_id: 2141744-1
    detail.hit.zdb_id: 1474604-9
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Evidence That the Pertussis Toxin-sensitive Trimeric GTP-binding Protein Gi2 Is Required for Agonist- and Store-activated Ca2+ Inflow in Hepatocytes
    Elsevier BV ; 1995
    In:  Journal of Biological Chemistry Vol. 270, No. 43 ( 1995-10), p. 25893-25897
    Details
    In: Journal of Biological Chemistry, Elsevier BV, Vol. 270, No. 43 ( 1995-10), p. 25893-25897
    Type of Medium: Online Resource
    ISSN: 0021-9258
    URL: Article
    DOI: 10.1074/jbc.270.43.25893
    Language: English
    Publisher: Elsevier BV
    Publication Date: 1995
    detail.hit.zdb_id: 2141744-1
    detail.hit.zdb_id: 1474604-9
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  • 6
    Online Resource
    Online Resource
    Phosphorylation of Neuronal and Endothelial Nitric Oxide Synthase in the Kidney with High and Low Salt Diets
    S. Karger AG ; 2006
    In:  Nephron Physiology Vol. 102, No. 2 ( 2006-1-9), p. p36-p50
    Details
    In: Nephron Physiology, S. Karger AG, Vol. 102, No. 2 ( 2006-1-9), p. p36-p50
    Abstract: 〈 i 〉 Background: 〈 /i 〉 Renal nitric oxide (NO) synthesis increases with increasing salt intake, however, the mechanisms underlying this are poorly understood. We hypothesized that activating or inhibitory phosphorylation of neuronal and endothelial nitric oxide synthase (nNOS, eNOS) regulates renal NO production in response to altered dietary salt. 〈 i 〉 Methods: 〈 /i 〉 Sprague-Dawley rats were fed low, normal or high salt diets for 12 h or 2 weeks, and kidney NOS phosphorylation was analyzed by Western blot using phosphopeptide antibodies against the sites nNOS-Ser 〈 sup 〉 1412 〈 /sup 〉 , nNOS-Ser 〈 sup 〉 847 〈 /sup 〉 , eNOS-Ser 〈 sup 〉 1176 〈 /sup 〉 and eNOS-Thr 〈 sup 〉 494 〈 /sup 〉 . 〈 i 〉 Results: 〈 /i 〉 At 12 h, total nNOS increased 1.4-fold (p 〈 0.01) in the high salt group and decreased by 26% (p 〈 0.05) in the low salt group. Changes in expression of phospho-nNOS at 12 h were accounted for by the changes in total nNOS. No change in total or phospho-eNOS was seen at 12 h. At 2 weeks, in the low salt group expression of total nNOS increased 1.8-fold (p 〈 0.05) whereas expression of nNOS phosphorylated at the inhibitory site Ser 〈 sup 〉 847 〈 /sup 〉 increased 4.3-fold (p 〈 0.01). Total eNOS was increased 3-fold in the low salt group (p 〈 0.01), with parallel increases in eNOS phosphorylated at both activating and inhibitory sites (p 〈 0.05). In the 2-week high salt group no changes in NOS expression or phosphorylation were seen, despite the observed increased excretion of urinary NO metabolites. 〈 i 〉 Conclusion: 〈 /i 〉 In summary, changes in phospho-nNOS and phospho-eNOS expression occurred in parallel with changes in total expression, thus, the overall activating and inhibitory effects of nNOS and eNOS phosphorylation at the sites studied were not changed by altered dietary salt.
    Type of Medium: Online Resource
    ISSN: 1660-2137
    URL: Article
    DOI: 10.1159/000089092
    Language: English
    Publisher: S. Karger AG
    Publication Date: 2006
    detail.hit.zdb_id: 2098340-2
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  • 7
    Online Resource
    Online Resource
    Recruitment of Thr 319-phosphorylated Ndd1p to the FHA domain of Fkh2p requires Clbkinase activity: a mechanism for CLB cluster gene activation
    Cold Spring Harbor Laboratory ; 2003
    In:  Genes & Development Vol. 17, No. 14 ( 2003-07-15), p. 1789-1802
    Details
    In: Genes & Development, Cold Spring Harbor Laboratory, Vol. 17, No. 14 ( 2003-07-15), p. 1789-1802
    Abstract: Activation of the CLB gene cluster through the assembly of Mcm1p–Fkh2p complexes at target promoters is essential for mitotic entry and transition through M phase. We show that the activation of this mitotic transcriptional program is dependent on the recruitment of Ndd1p, a coactivator that performs its essential function by acting through Fkh2p. Although an essential gene, NDD1 is dispensable in cells expressing a truncated form of Fkh2p lacking its C terminus. When phosphorylated on T319, Ndd1p is recruited to CLB cluster promoters by association with the forkhead-associated (FHA) domain of Fkh2p. Substitution of T319 for alanine significantly reduces recruitment of Ndd1p, resulting in loss of normal transcriptional regulation, severe impairment of cell growth, and a budding defect reminiscent of cells with a Cdk-Clbkinase deficiency. Finally, we show that phosphorylation of T319 and recruitment of Ndd1p to CLB2 and SWI5 promoters is dependent on Cdc28-Clbkinase activity. These data provide a model describing the activation of G2/M transcription through the phosphorylation of Ndd1p by Cdc28-Clb kinase activity.
    Type of Medium: Online Resource
    ISSN: 0890-9369 , 1549-5477
    URL: Article
    DOI: 10.1101/gad.1074103
    RVK:
    WA 15000
    Language: English
    Publisher: Cold Spring Harbor Laboratory
    Publication Date: 2003
    detail.hit.zdb_id: 1467414-2
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  • 8
    Online Resource
    Online Resource
    Protein tyrosine phosphatase hPTPN20a is targeted to sites of actin polymerization
    Portland Press Ltd. ; 2005
    In:  Biochemical Journal Vol. 389, No. 2 ( 2005-07-15), p. 343-354
    Details
    In: Biochemical Journal, Portland Press Ltd., Vol. 389, No. 2 ( 2005-07-15), p. 343-354
    Abstract: The human genome encodes 38 classical tyrosine-specific PTPs (protein tyrosine phosphatases). Many PTPs have been shown to regulate fundamental cellular processes and several are mutated in human diseases. We report that the product of the PTPN20 gene at the chromosome locus 10q11.2 is alternatively spliced to generate 16 possible variants of the classical human non-transmembrane PTP 20 (hPTPN20). One of these variants, hPTPN20a, was expressed in a wide range of both normal and transformed cell lines. The catalytic domain of hPTPN20 exhibited catalytic activity towards tyrosyl phosphorylated substrates, confirming that it is a bona fide PTP. In serum-starved COS1 cells, hPTPN20a was targeted to the nucleus and the microtubule network, colocalizing with the microtubule-organizing centre and intracellular membrane compartments, including the endoplasmic reticulum and the Golgi apparatus. Stimulation of cells with epidermal growth factor, osmotic shock, pervanadate, or integrin ligation targeted hPTPN20a to actin-rich structures that included membrane ruffles. The present study identifies hPTPN20a as a novel and widely expressed phosphatase with a dynamic subcellular distribution that is targeted to sites of actin polymerization.
    Type of Medium: Online Resource
    ISSN: 0264-6021 , 1470-8728
    URL: Article
    DOI: 10.1042/BJ20041932
    RVK:
    WA 15000
    Language: English
    Publisher: Portland Press Ltd.
    Publication Date: 2005
    detail.hit.zdb_id: 1473095-9
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  • 9
    Online Resource
    Online Resource
    Acute renal ischemia rapidly activates the energy sensor AMPK but does not increase phosphorylation of eNOS-Ser 1177
    American Physiological Society ; 2005
    In:  American Journal of Physiology-Renal Physiology Vol. 289, No. 5 ( 2005-11), p. F1103-F1115
    Details
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 289, No. 5 ( 2005-11), p. F1103-F1115
    Abstract: A fundamental aspect of acute renal ischemia is energy depletion, manifest as a falling level of ATP that is associated with a simultaneous rise in AMP. The energy sensor AMP-activated protein kinase (AMPK) is activated by a rising AMP-to-ATP ratio, but its role in acute renal ischemia is unknown. AMPK is activated in the ischemic heart and is reported to phosphorylate both endothelial nitric oxide synthase (eNOS) and acetyl-CoA carboxylase. To study activation of AMPK in acute renal ischemia, the renal pedicle of anesthetized Sprague-Dawley rats was cross-clamped for increasing time intervals. AMPK was strongly activated within 1 min and remained so after 30 min. However, despite the robust activation of AMPK, acute renal ischemia did not increase phosphorylation of the AMPK phosphorylation sites eNOS-Ser 1177 or acetyl-CoA carboxylase-Ser 79 . Activation of AMPK in bovine aortic endothelial cells by the ATP-depleting agent antimycin A and the antidiabetic drug phenformin also did not increase phosphorylation of eNOS-Ser 1177 , confirming that AMPK activation and phosphorylation of eNOS are dissociated in some situations. Immunoprecipitation studies demonstrated that the dissociation between AMPK activation and phosphorylation of eNOS-Ser 1177 was not due to changes in the physical associations between AMPK, eNOS, or heat shock protein 90. In conclusion, acute renal ischemia rapidly activates the energy sensor AMPK, which is known to maintain ATP reserves during energy stress. The substrates it phosphorylates, however, are different from those in other organs such as the heart.
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    URL: Article
    DOI: 10.1152/ajprenal.00458.2004
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2005
    detail.hit.zdb_id: 1477287-5
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  • 10
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    Online Resource
    Low salt concentrations activate AMP-activated protein kinase in mouse macula densa cells
    American Physiological Society ; 2009
    In:  American Journal of Physiology-Renal Physiology Vol. 296, No. 4 ( 2009-04), p. F801-F809
    Details
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 296, No. 4 ( 2009-04), p. F801-F809
    Abstract: The energy-sensing kinase AMP-activated protein kinase (AMPK) is associated with the sodium-potassium-chloride cotransporter NKCC2 in the kidney and phosphorylates it on a regulatory site in vitro. To identify a potential role for AMPK in salt sensing at the macula densa, we have used the murine macula densa cell line MMDD1. In this cell line, AMPK was rapidly activated by isosmolar low-salt conditions. In contrast to the known salt-sensing pathway in the macula densa, AMPK activation occurred in the presence of either low sodium or low chloride and was unaffected by inhibition of NKCC2 with bumetanide. Assays using recombinant AMPK demonstrated activation of an upstream kinase by isosmolar low salt. The specific calcium/calmodulin-dependent kinase kinase inhibitor STO-609 failed to suppress AMPK activation, suggesting that it was not part of the signal pathway. AMPK activation was associated with increased phosphorylation of the specific substrate acetyl-CoA carboxylase (ACC) at Ser 79 , as well as increased NKCC2 phosphorylation at Ser 126 . AMPK activation due to low salt concentrations was inhibited by an adenovirus construct encoding a kinase dead mutant of AMPK, leading to reduced ACC Ser 79 and NKCC2 Ser 126 phosphorylation. This work demonstrates that AMPK activation in macula densa-like cells occurs via isosmolar changes in sodium or chloride concentration, leading to phosphorylation of ACC and NKCC2. Phosphorylation of these substrates in vivo is predicted to increase intracellular chloride and so reduce the effect of salt restriction on tubuloglomerular feedback and renin secretion.
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    URL: Article
    DOI: 10.1152/ajprenal.90372.2008
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2009
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