| 1. |
- Sterlini, B, et al.
(författare)
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An interaction between PRRT2 and Na+/K+ ATPase contributes to the control of neuronal excitability
- 2021
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Ingår i: Cell death & disease. - : Springer Science and Business Media LLC. - 2041-4889. ; 12:4, s. 292-
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Tidskriftsartikel (refereegranskat)abstract
- Mutations in PRoline Rich Transmembrane protein 2 (PRRT2) cause pleiotropic syndromes including benign infantile epilepsy, paroxysmal kinesigenic dyskinesia, episodic ataxia, that share the paroxysmal character of the clinical manifestations. PRRT2 is a neuronal protein that plays multiple roles in the regulation of neuronal development, excitability, and neurotransmitter release. To better understand the physiopathology of these clinical phenotypes, we investigated PRRT2 interactome in mouse brain by a pulldown-based proteomic approach and identified α1 and α3 Na+/K+ ATPase (NKA) pumps as major PRRT2-binding proteins. We confirmed PRRT2 and NKA interaction by biochemical approaches and showed their colocalization at neuronal plasma membrane. The acute or constitutive inactivation of PRRT2 had a functional impact on NKA. While PRRT2-deficiency did not modify NKA expression and surface exposure, it caused an increased clustering of α3-NKA on the plasma membrane. Electrophysiological recordings showed that PRRT2-deficiency in primary neurons impaired NKA function during neuronal stimulation without affecting pump activity under resting conditions. Both phenotypes were fully normalized by re-expression of PRRT2 in PRRT2-deficient neurons. In addition, the NKA-dependent afterhyperpolarization that follows high-frequency firing was also reduced in PRRT2-silenced neurons. Taken together, these results demonstrate that PRRT2 is a physiological modulator of NKA function and suggest that an impaired NKA activity contributes to the hyperexcitability phenotype caused by PRRT2 deficiency.
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| 4. |
- Lal, M. A., et al.
(författare)
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Role of oxidative stress in advanced glycation end product-induced mesangial cell activation
- 2002
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Ingår i: Kidney International. - : Elsevier BV. - 0085-2538 .- 1523-1755. ; 61:6, s. 2006-2014
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Tidskriftsartikel (refereegranskat)abstract
- Background. Levels of advanced glycation end products (AGE) are elevated in individuals with advancing age, renal failure, and diabetes, and accumulation of these molecules may contribute to disease progression. The mechanism by which AGE proteins alter glomerular mesangial cell function, however, is not completely understood. The present study assessed the involvement of oxidative stress in AGE-dependent mesangial cell signaling events. Methods. Primary cultures of rat renal mesangial cells were exposed to in vitro AGE-BSA and H-2 O-2 . Nuclear factor-kappaB (NF-kappaB) and protein kinase C (PKC) isoform activation were studied using confocal microscopy and Western blotting. Quantitative polymerase chain reaction (PCR) was used to measure transforming growth factor-beta1 (TGF-beta1) levels. The involvement of oxidative stress was assessed by supplementing or compromising cellular antioxidant capacity. Results. NF-kappaB was dose-dependently activated by AGE. PKC activation was not involved in this response, but analysis of PKC-beta1 activation showed a stimulatory effect of AGE proteins on this isoform. Transcription of TGF-beta1 was stimulated by AGE and was prevented by PKC inhibition. Challenge with H-2 O-2 had similar downstream effects on mesangial cell signaling. Antioxidants, vitamin E and nitecapone, prevented AGE-dependent NF-kappaB activation and normalized PKC activity and associated TGF-beta1 transcription. Depletion of the intracellular antioxidant, glutathione, effectively lowered the AGE concentration needed for mesangial cell activation of NF-kappaB and PKC-beta1. Treatment with a suboptimal AGE dose, under glutathione-depleted conditions, revealed a synergistic effect on both parameters. Conclusion. The results support a central role for oxidative stress in AGE-dependent mesangial cell signaling and emphasize the importance of ROS in determining cell responsiveness.
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| 6. |
- Uhlen, P., et al.
(författare)
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alpha-Haemolysin of uropathogenic E-coli induces Ca2+ oscillations in renal epithelial cells
- 2000
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 405:6787, s. 694-697
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Tidskriftsartikel (refereegranskat)abstract
- Pyelonephritis is one of the most common febrile diseases in children. If not treated appropriately, it causes irreversible renal damage and accounts for a large proportion of end stage renal failures(1). Renal scarring can occur in the absence of inflammatory cells, indicating that bacteria may have a direct signalling effect on renal cells(2). Intracellular calcium ([Ca2+](i)) oscillations can protect cells from the cytotoxic effects of prolonged increases in intracellular calcium(3,4). However, no pathophysiologically relevant protein that induces such oscillations has been identified. Here we show that infection by uropathogenic Escherichia coli induces a constant, low-frequency oscillatory [Ca2+](i) response in target primary rat renal epithelial cells induced by the secreted RTX (repeats-in-toxin) toxin alpha-haemolysin. The response depends on calcium influx through L-type calcium channels as well as from internal stores gated by inositol triphosphate. Internal calcium oscillations induced by alpha-haemolysin in a renal epithelial cell line stimulated production of cytokines interleukin (IL)-6 and IL-8. Our findings indicate a novel role for alpha-haemolysin in pyelonephritis: as an inducer of an oscillating second messenger response in target cells, which fine-tunes gene expression during the inflammatory response.
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| 7. |
- Zelenina, M., et al.
(författare)
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Water permeability of aquaporin-4 is decreased by protein kinase C and dopamine
- 2002
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Ingår i: American Journal of Physiology - Renal Physiology. - : American Physiological Society. - 0363-6127 .- 1522-1466 .- 1931-857X. ; 283:2, s. F309-F318
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Tidskriftsartikel (refereegranskat)abstract
- Aquaporin-4 (AQP4) plays an important role in the basolateral movement of water in the collecting duct. Here we show that this water channel can be dynamically regulated. Water permeability (P-f) was measured in individual LLC-PK1 cells that were transiently transfected with AQP4. To identify which cells were transfected, AQP4 was tagged at the NH2 terminus with green fluorescent protein. Transfected cells showed a strong fluorescent signal in basolateral membrane and a low-to-negligible signal in the cytosol and apical membrane. Activation of protein kinase C (PKC) with phorbol 12,13-dibutyrate (PDBu) significantly decreased P-f of cells expressing AQP4 but had no effect on neighboring untransfected cells. No redistribution of AQP4 in response to PDBu was detected. Dopamine also decreased the P-f in transfected cells. The effect was abolished by the PKC inhibitor Ro 31-8220. Reduction of AQP4 water permeability by PDBu and dopamine was abolished by point mutation of Ser(180), a consensus site for PKC phosphorylation. We conclude that PKC and dopamine decrease AQP4 water permeability via phosphorylation at Ser(180) and that the effect is likely mediated by gating of the channel.
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| 8. |
- Aizman, O, et al.
(författare)
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Anatomical and physiological evidence for D-1 and D-2 dopamine receptor colocalization in neostriatal neurons
- 2000
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Ingår i: Nature Neuroscience. - : Springer Science and Business Media LLC. - 1097-6256 .- 1546-1726. ; 3:3, s. 226-230
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Tidskriftsartikel (refereegranskat)abstract
- Despite the importance of dopamine signaling, it remains unknown if the two major subclasses of dopamine receptors exist on the same or distinct populations of neurons. Here we used confocal microscopy to demonstrate that virtually all striatal neurons, both in vitro and in vivo, contained dopamine receptors of both classes. We also provide functional evidence for such colocalization: in essentially all neurons examined, fenoldopam, an agonist of the D-1 subclass of receptors, inhibited both the Na+/K+ pump and tetrodotoxin (TTX)-sensitive sodium channels, and quinpirole, an agonist of the Dr subclass of receptors, activated TTX-sensitive sodium channels. Thus D-1 and D-2 classes of ligands may functionally interact in virtually all dopamine-responsive neurons within the basal ganglia.
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| 9. |
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| 10. |
- Bottger, P, et al.
(författare)
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Glutamate-system defects behind psychiatric manifestations in a familial hemiplegic migraine type 2 disease-mutation mouse model
- 2016
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Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6, s. 22047-
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Tidskriftsartikel (refereegranskat)abstract
- Migraine is a complex brain disorder, and understanding the complexity of this prevalent disease could improve quality of life for millions of people. Familial Hemiplegic Migraine type 2 (FHM2) is a subtype of migraine with aura and co-morbidities like epilepsy/seizures, cognitive impairments and psychiatric manifestations, such as obsessive-compulsive disorder (OCD). FHM2 disease-mutations locate to the ATP1A2 gene encoding the astrocyte-located α2-isoform of the sodium-potassium pump (α2Na+/K+-ATPase). We show that knock-in mice heterozygous for the FHM2-associated G301R-mutation (α2+/G301R) phenocopy several FHM2-relevant disease traits e.g., by mimicking mood depression and OCD. In vitro studies showed impaired glutamate uptake in hippocampal mixed astrocyte-neuron cultures from α2G301R/G301R E17 embryonic mice, and moreover, induction of cortical spreading depression (CSD) resulted in reduced recovery in α2+/G301R male mice. Moreover, NMDA-type glutamate receptor antagonists or progestin-only treatment reverted specific α2+/G301R behavioral phenotypes. Our findings demonstrate that studies of an in vivo relevant FHM2 disease knock-in mouse model provide a link between the female sex hormone cycle and the glutamate system and a link to co-morbid psychiatric manifestations of FHM2.
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| 11. |
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| 14. |
- Illarionova, N. B., et al.
(författare)
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FUNCTIONAL AND MOLECULAR INTERACTIONS BETWEEN AQUAPORINS AND Na,K-ATPase
- 2010
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Ingår i: Neuroscience. - : Elsevier BV. - 0306-4522 .- 1873-7544. ; 168:4, s. 915-925
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Tidskriftsartikel (refereegranskat)abstract
- The water channel aquaporin 4 (AQP4) is abundantly expressed in astrocytes and provides a mechanism by which water permeability of the plasma membrane can be regulated. Astrocytes play a key role in the clearance of both potassium (K+) and glutamate released during neuronal activity. Emerging evidence suggests that AQP4 facilitates K+ clearance by astrocytes and contributes to recovery of neuronal excitability. Here we report that AQP4 can assemble with its regulator metabotropic glutamate receptor 5 (mGluR5) and with Na,K-ATPase; the enzyme responsible for active K+ transport and for establishing the electrochemical gradient across the cell plasma membrane. We have, by use of pull down assays in rat brain tissue, identified the segment in the AQP4 NH2-terminus containing the amino acid residues 23-32 as the site for interaction with Na,K-ATPase catalytic subunit and with mGluR5. Mutagenesis studies revealed that the AQP4 amino acids K27 and W30 are of key importance for interaction with both Na,K-ATPase and mGluR5. To confirm that interaction also occurs within intact cells, we have performed fluorescence resonance energy transfer (FRET) studies in primary astrocytes derived from rat striatum. The results indicate close proximity of wild type AQP4 and Na,K-ATPase in the plasma membrane of rat astrocytes. FRET efficiencies observed with the mutants AQP4 K27A and AQP4 W30A were significantly lower, highlighting the importance of these residues for the interaction between AQP4 and Na,K-ATPase. We conclude that AQP4/Na,K-ATPase/mGluR5 can form a macromolecular complex/transporting microdomain in astrocytes. This complex may be of functional importance for the regulation of water and K+ homeostasis in the brain, as well as for neuron-astrocyte metabolic crosstalk. (C) 2010 IBRO. Published by Elsevier Ltd. All rights reserved.
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| 18. |
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| 19. |
- Lal, MA, et al.
(författare)
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Combined antioxidant and COMT inhibitor treatment reverses renal abnormalities in diabetic rats
- 2000
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 49:8, s. 1381-1389
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Tidskriftsartikel (refereegranskat)abstract
- The development and progression of diabetic nephropathy is dependent on glucose homeostasis and many other contributing factors. In the present study, we examined the effect of nitecapone, an inhibitor of the dopamine-metabolizing enzyme catechol-O-methyl transferase (COMT) and a potent antioxidant, on functional and cellular determinants of renal function in rats with streptozotocin-induced diabetes. Administration of nitecapone to diabetic rats normalized urinary sodium excretion in a manner consistent with the dopamine-dependent inhibition of proximal tubule Na,K-ATPase activity. Hyperfiltration, focal glomerulosclerosis, and albuminuria were also reversed by nitecapone, but in a manner that is more readily attributed to the antioxidant potential of the agent. A pattern of elevated oxidative stress, measured as CuZn superoxide dismutase gene expression and thiobarbituric acid-reactive substance content, was noted in diabetic rats, and both parameters were normalized by nitecapone treatment. In diabetic rats, activation of glomerular protein kinase C (PKC) was confirmed by isoform-specific translocation and Ser23 phosphorylation of the PKC substrate Na,K-ATPase. PKC-dependent changes in Na,K-ATPase phosphorylation were associated with decreased glomerular Na,K-ATPase activity. Nitecapone-treated diabetic rats were protected from these intracellular modifications. The combined results suggest that the COMT-inhibitory and antioxidant properties of nitecapone provide a protective therapy against the development of diabetic nephropathy.
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| 20. |
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| 21. |
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| 22. |
- Miyakawa-Naito, A., et al.
(författare)
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Cell signaling Microdomain with Na,K-ATPase and inositol 1,4,5-trisphosphate receptor generates calcium oscillations
- 2003
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 17:4, s. A43-A43
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies indicate novel roles for the ubiquitous ion pump, Na,K-ATPase, in addition to its function as a key regulator of intracellular sodium and potassium concentration. We have previously demonstrated that ouabain, the endogenous ligand of Na, K-ATPase, can trigger intracellular Ca2+ oscillations, a versatile intracellular signal controlling a diverse range of cellular processes. Here we report that Na, K-ATPase and inositol 1,4,5-trisphosphate (InsP(3)) receptor (InsP(3)R) form a cell signaling microdomain that, in the presence of ouabain, generates slow Ca2+ oscillations in renal cells. Using fluorescent resonance energy transfer ( FRET) measurements, we detected a close spatial proximity between Na, K-ATPase and InsP(3)R. Ouabain significantly enhanced FRET between Na, K-ATPase and InsP(3)R. The FRET effect and ouabain-induced Ca2+ oscillations were not observed following disruption of the actin cytoskeleton. Partial truncation of the NH2 terminus of Na, K-ATPase catalytic alpha1-subunit abolished Ca2+ oscillations and downstream activation of NF-kappaB. Ouabain-induced Ca2+ oscillations occurred in cells expressing an InsP3 sponge and were hence independent of InsP3 generation. Thus, we present a novel principle for a cell signaling microdomain where an ion pump serves as a receptor.
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| 25. |
- Nishimoto, G, et al.
(författare)
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Arginine vasopressin stimulates phosphorylation of aquaporin-2 in rat renal tissue.
- 1999
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Ingår i: American Journal of Physiology. - 0002-9513 .- 2163-5773. ; 276:2 Pt 2, s. F254-9
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Tidskriftsartikel (refereegranskat)abstract
- Aquaporin-2 (AQP2), the protein that mediates arginine vasopressin (AVP)-regulated apical water transport in the renal collecting duct, possesses a single consensus phosphorylation site for cAMP-dependent protein kinase A (PKA) at Ser256. The aim of this study was to examine whether AVP, and other agents that increase cAMP levels, could stimulate the phosphorylation of AQP2 in intact rat renal tissue. Rat renal papillae were prelabeled with 32P and incubated with vehicle or drugs, and then AQP2 was immunoprecipitated. Two polypeptides corresponding to nonglycosylated (29 kDa) and glycosylated (35-48 kDa) AQP2 were identified by SDS-PAGE. AVP caused a time- and dose-dependent increase in phosphorylation of both glycosylated and nonglycosylated AQP2. The threshold dose for a significant increase in phosphorylation was 10 pM, which corresponds to a physiological serum concentration of AVP. Maximal phosphorylation was reached within 1 min of AVP incubation. This effect on AQP2 phosphorylation was mimicked by the vasopressin (V2) agonist, 1-desamino-[8-D-arginine]vasopressin (DDAVP), or forskolin. Two-dimensional phosphopeptide mapping indicated that AVP and forskolin stimulated the phosphorylation of the same site in AQP2. Immunoblot analysis using a phosphorylation state-specific antiserum revealed an increase in phosphorylation of Ser256 after incubation of papillae with AVP. The results indicate that AVP stimulates phosphorylation of AQP2 at Ser256 via activation of PKA, supporting the idea that this is one of the first steps leading to increased water permeability in collecting duct cells.
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