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Janos Petipeterdi - One of the best experts on this subject based on the ideXlab platform.

  • atp releasing Connexin 30 hemichannels mediate flow induced calcium signaling in the collecting duct
    Frontiers in Physiology, 2013
    Co-Authors: James L Burford, Per Svenningsen, Janos Petipeterdi
    Abstract:

    ATP in the renal tubular fluid is an important regulator of salt and water reabsorption via purinergic calcium signaling that involves the P2Y2 receptor, ENaC and AQP2. Recently, we have shown that Connexin (Cx) 30 hemichannels are localized to the non-junctional apical membrane of cells in the distal nephron-collecting duct (CD) and release ATP into the tubular fluid upon mechanical stimuli, leading to reduced salt and water reabsorption. Cx30-/- mice show salt-dependent elevations in BP and impaired pressure-natriuresis. Thus, we hypothesized that increased tubular flow rate leads to Cx30-dependent purinergic intracellular calcium ([Ca2+]i) signaling in the CD. Cortical CDs (CCDs) from wild type and Cx30-/- mice were freshly dissected and microperfused in vitro. Using confocal fluorescence imaging and the calcium-sensitive fluorophore pair Fluo-4 and Fura Red, we found that increasing tubular flow rate from 2 to 20 nl/min caused a significant 2.1-fold elevation in [Ca2+]i in wild type CCDs. This response was blunted in Cx30-/- CCDs ([Ca2+]i increased only 1.2-fold, p

  • diminished paracrine regulation of the epithelial na channel by purinergic signaling in mice lacking Connexin 30
    Journal of Biological Chemistry, 2011
    Co-Authors: Elena Mironova, Janos Petipeterdi, Vladislav Bugaj, James D Stockand
    Abstract:

    Abstract We tested whether ATP release through Connexin 30 (Cx30) is part of a local purinergic regulatory system intrinsic to the aldosterone-sensitive distal nephron (ASDN) important for proper control of sodium excretion; if changes in sodium intake influence ATP release via Cx30; and if this allows a normal ENaC response to changes in systemic sodium levels. In addition, we define the consequences of disrupting ATP regulation of ENaC in Cx30−/− mice. Urinary ATP levels in wild-type mice increase with sodium intake, being lower and less dependent on sodium intake in Cx30−/− mice. Loss of inhibitory ATP regulation causes ENaC activity to be greater in Cx30−/− versus wild-type mice, particularly with high sodium intake. This results from compromised ATP release rather than end-organ resistance: ENaC in Cx30−/− mice responds to exogenous ATP. Thus, loss of paracrine ATP feedback regulation of ENaC in Cx30−/− mice disrupts normal responses to changes in sodium intake. Consequently, ENaC is hyperactive in Cx30−/− mice lowering sodium excretion particularly during increases in sodium intake. Clamping mineralocorticoids high in Cx30−/− mice fed a high sodium diet causes a marked decline in renal sodium excretion. This is not the case in wild-type mice, which are capable of undergoing aldosterone-escape. This loss of the ability of ENaC to respond to changes in sodium levels contributes to salt-sensitive hypertension in Cx30−/− mice.

  • Connexin 30 deficiency impairs renal tubular atp release and pressure natriuresis
    Journal of The American Society of Nephrology, 2009
    Co-Authors: Arnold Sipos, Klaus Willecke, Sarah L Vargas, Ildiko Toma, Fiona Hanner, Janos Petipeterdi
    Abstract:

    In the renal tubule, ATP is an important regulator of salt and water reabsorption, but the mechanism of ATP release is unknown. Several Connexin (Cx) isoforms form mechanosensitive, ATP-permeable hemichannels. We localized Cx30 to the nonjunctional apical membrane of cells in the distal nephron and tested whether Cx30 participates in physiologically important release of ATP. We dissected, partially split open, and microperfused cortical collecting ducts from wild-type and Cx30-deficient mice in vitro . We used PC12 cells as ATP biosensors by loading them with Fluo-4/Fura Red to measure cytosolic calcium and positioning them in direct contact with the apical surface of either intercalated or principal cells. ATP biosensor responses, triggered by increased tubular flow or by bath hypotonicity, were approximately three-fold greater when positioned next to intercalated cells than next to principal cells. In addition, these responses did not occur in preparations from Cx30-deficient mice or with purinergic receptor blockade. After inducing step increases in mean arterial pressure by ligating the distal aorta followed by the mesenteric and celiac arteries, urine output increased 4.2-fold in wild-type mice compared with 2.6-fold in Cx30-deficient mice, and urinary Na + excretion increased 5.2-fold in wild-type mice compared with 2.8-fold in Cx30-deficient mice. Furthermore, Cx30-deficient mice developed endothelial sodium channel–dependent, salt-sensitive elevations in mean arterial pressure. Taken together, we suggest that mechanosensitive Cx30 hemichannels have an integral role in pressure natriuresis by releasing ATP into the tubular fluid, which inhibits salt and water reabsorption.

  • Connexin 30 3 is expressed in the kidney but not regulated by dietary salt or high blood pressure
    Cell Communication and Adhesion, 2008
    Co-Authors: Fiona Hanner, Klaus Willecke, Ildiko Toma, Marc Schnichels, Qingyi Zhengfischhofer, Li E Yang, Alicia A Mcdonough, Janos Petipeterdi
    Abstract:

    Several isoforms of Connexin (Cx) proteins have been identified in a variety of tissues where they play a role in intercellular communication, either as the components of gap junctions or as large, nonselective pores known as hemichannels. This investigation seeks to identify the localization and regulation of Cx30.3 in mouse, rat, and rabbit kidney using a Cx30.3+/lacZ transgenic approach and immunofluorescence. Cx30.3 was detected in all three species and predominantly in the renal medulla. Both the nuclear lacZ staining indicative of Cx30.3 expression and indirect immunohistochemistry provided the same results. Cx30.3 immunolabeling was mainly punctate in the mouse, typical for gap junctions. In contrast, it showed continuous apical plasma membrane localization in certain tubule segments in the rat and rabbit kidney, suggesting that it may also function as hemichannels. In the cortex, Cx30.3 was localized in the intercalated cells of the cortical collecting duct, because the immunoreactive cells did no...

  • localization of Connexin 30 in the luminal membrane of cells in the distal nephron
    American Journal of Physiology-renal Physiology, 2005
    Co-Authors: Fiona Mcculloch, Regine Chambrey, Dominique Eladari, Janos Petipeterdi
    Abstract:

    Several isoforms of the gap junction protein Connexin (Cx) have been identified in a variety of tissues that communicate intercellular signals between adjacent cells. In the kidney, Cx37, Cx40, and...

Gregory Ghezali - One of the best experts on this subject based on the ideXlab platform.

  • neuronal activity drives astroglial Connexin 30 in perisynaptic processes and shapes its functions
    Cerebral Cortex, 2020
    Co-Authors: Gregory Ghezali, Pascal Ezan, Martine Cohensalmon, Flora Vasile, Nathan Curry, Marcus Fantham, Giselle Cheung, Clemens F Kaminski, Nathalie Rouach
    Abstract:

    : Astrocytes play key roles in brain functions through dynamic interactions with neurons. One of their typical features is to express high levels of Connexins (Cxs), Cx43 and Cx30, the gap junction (GJ)-forming proteins. Cx30 is involved in basic cognitive processes and shapes synaptic and network activities, as shown by recent studies in transgenic animals. Yet it remains unknown whether astroglial Cx30 expression, localization, and functions are endogenously and dynamically regulated by neuronal activity and could therefore play physiological roles in neurotransmission. We here show that neuronal activity increased hippocampal Cx30 protein levels via a posttranslational mechanism regulating lysosomal degradation. Neuronal activity also increased Cx30 protein levels at membranes and perisynaptic processes, as revealed by superresolution imaging. This translated at the functional level in the activation of Cx30 hemichannels and in Cx30-mediated remodeling of astrocyte morphology independently of GJ biochemical coupling. Altogether, these data show activity-dependent dynamics of Cx30 expression, perisynaptic localization, and functions.

  • Connexin 30 controls astroglial polarization during postnatal brain development
    Development, 2018
    Co-Authors: Gregory Ghezali, Charlesfelix Calvo, Laureelise Pillet, Flora Llense, Pascal Ezan, Ulrike Pannasch, Alexispierre Bemelmans, Sandrine Etienne Manneville
    Abstract:

    ABSTRACT Astrocytes undergo intense morphological maturation during development, changing from individual sparsely branched cells to polarized and tremendously ramified cells. Connexin 30, an astroglial gap-junction channel-forming protein expressed postnatally, regulates in situ the extension and ramification of astroglial processes. However, the involvement of Connexin 30 in astroglial polarization, which is known to control cell morphology, remains unexplored. We found that Connexin 30, independently of gap-junction-mediated intercellular biochemical coupling, alters the orientation of astrocyte protrusion, centrosome and Golgi apparatus during polarized migration in an in vitro wound-healing assay. Connexin 30 sets the orientation of astroglial motile protrusions via modulation of the laminin/β1 integrin/Cdc42 polarity pathway. Connexin 30 indeed reduces laminin levels, inhibits the redistribution of the β1-integrin extracellular matrix receptors, and inhibits the recruitment and activation of the small Rho GTPase Cdc42 at the leading edge of migrating astrocytes. In vivo , Connexin 30, the expression of which is developmentally regulated, also contributes to the establishment of hippocampal astrocyte polarity during postnatal maturation. This study thus reveals that Connexin 30 controls astroglial polarity during development.

  • control of synaptic transmission by astroglial Connexin 30 molecular basis activity dependence and physiological implication
    2016
    Co-Authors: Gregory Ghezali
    Abstract:

    Perisynaptic astrocytes are active partners of neurons in cerebral information processing. A key property of astrocytes is to express high levels of the gap junction forming proteins, the Connexins (Cxs). Strikingly, astroglial Cx30 was suggested early on to be involved in cognitive processes; however, its specific role in neurophysiology has yet been unexplored. We recently reveal that Cx30, through an unconventional non-channel function, controls hippocampal glutamatergic synaptic strength and plasticity by directly setting synaptic glutamate levels through astroglial glutamate clearance. Yet the cellular and molecular mechanisms involved in such control, its dynamic regulation by activity and its impact in vivo in a physiological context were unknown. To answer these questions, I demonstrated during my PhD that: 1) Cx30 drives the morphological maturation of hippocampal astrocytes via the modulation of a laminin signaling pathway regulating cell polarization; 2) Cx30 expression, perisynaptic localization and functions are modulated by neuronal activity; 3) Cx30-mediated control of astrocyte synapse coverage in the supraoptic nucleus of the hypothalamus sets basal plasmatic level of the neurohormone oxytocin and hence promotes appropriate oxytocin-based social abilities. Taken together, these data shed new light on astroglial Cxs activity-dependent regulations and roles in the postnatal development of neuroglial networks, as well as in astrocyte-synapse structural interactions mediating behavioral processes.

  • Connexin 30 sets synaptic strength by controlling astroglial synapse invasion
    Nature Neuroscience, 2014
    Co-Authors: Gregory Ghezali, Ulrike Pannasch, Dominik Freche, Glenn Dallerac, Carole Escartin
    Abstract:

    Astrocytes provide essential support for and modulate synaptic transmission between neurons. Here the authors show that non-channel functions of Connexin 30, a gap-junction subunit, control the synaptic coverage of astroglial processes and regulate glutamate clearance, synaptic strength and memory function.

Phillip A Wackym - One of the best experts on this subject based on the ideXlab platform.

  • Connexin 26 and Connexin 30 mutations in children with nonsyndromic hearing loss
    Laryngoscope, 2004
    Co-Authors: Christy B Erbe, Kevin C Harris, Christina L Rungesamuelson, Valerie A Flanary, Phillip A Wackym
    Abstract:

    Objectives/Hypothesis: Mutations in the Connexin 26 (Cx26) or gap junction beta 2 gene are the leading cause of hereditary nonsyndromic sensorineural hearing loss in Caucasians. The Cx26 coding region of 68 children with nonsyndromic sensorineural hearing loss was sequenced to determine the frequency and type of Cx26 mutations in this population. Screening was also performed for a common Connexin 30 (Cx30) or gap junction beta 6 mutation (del [GJB6-D13S1830]). Children also underwent audiological testing to determine whether any correlation exists between Cx26 mutations and severity of hearing loss. Study Design: In all, 68 children with nonsyndromic sensorineural hearing loss were screened for Cx26 and Cx30 mutations by polymerase chain reaction and direct sequencing. Methods: Genomic DNA was amplified by polymerase chain reaction using primers that flank the entire Cx26 coding region. Screening for the 342-kb Cx30 deletion was performed using primers that amplified the breakpoint junction of the deletion. The amplicons were then sequenced in both directions and analyzed for mutations. Audiometric testing, including pure-tone audiometry and auditory evoked brainstem response, was also performed to determine the degree of hearing loss. Results: Twenty-seven of 68 children tested had mutations in Cx26 with 35delG being the most prevalent. Ten additional Cx26 mutations were detected including a novel compound heterozygote. Two children were heterozygous for the Cx30 del (GJB6-D13S1830) mutation. Conclusion: Cx26 and Cx30 mutations were present in 41.2% of children tested in the study population. Audiometric data supported previous studies demonstrating a greater degree of hearing loss in subjects who are homozygous for the 35delG mutation.

Jiannjou Yang - One of the best experts on this subject based on the ideXlab platform.

  • the functional role of Connexin 26 mutation in nonsyndromic hearing loss demonstrated by zebrafish Connexin 30 3 homologue model
    Cells, 2020
    Co-Authors: Hsuanan Su, Jiannjou Yang, Shuanyow Li, Tzurong Su, Chingchyuan Su
    Abstract:

    Nonsyndromic hearing loss (NSHL) is of great clinical importance, and mutations in the GJB2 gene and the encoded human Connexin 26 (CX26) protein play important roles in the genetic pathogenesis. The CX26 p.R184Q mutation was shown to be a dominant-negative effect in our previous study. Previously, we also demonstrated that zebrafish Cx30.3 is orthologous to human CX26. In the present study, we established transgenic zebrafish models with mutated Cx30.3 specifically expressed in the supporting cells of zebrafish inner ears driven by the agr2 promoter, to demonstrate and understand the mechanism by which the human CX26 R.184 mutation causes NSHL. Our results indicated that significant structural changes in the inner ears of transgenic lines with mutations were measured and compared to wild-type zebrafish. Simultaneously, significant alterations of transgenic lines with mutations in swimming behavior were analyzed with the zebrafish behavioral assay. This is the first study to investigate the functional results of the CX26 p.R184Q mutation with in vivo disease models. Our work supports and confirms the pathogenic role of the CX26 p.R184Q mutation in NSHL, with a hypothesized mechanism of altered interaction among amino acids in the Connexins.

  • the Connexin 30 3 of zebrafish homologue of human Connexin 26 may play similar role in the inner ear
    Hearing Research, 2014
    Co-Authors: Ju Changchien, Kuohsuan Chien, Shaunyow Li, Jiannjou Yang
    Abstract:

    Abstract The intercellular gap junction channels formed by Connexins (CXs) are important for recycling potassium ions in the inner ear. CXs are encoded by a family of the CX gene, such as GJB2 , and the mechanism leading to mutant Connexin-associated diseases, including hearing loss, remains to be elucidated. In this study, using bioinformatics, we found that two zebrafish cx genes, cx27.5 and cx30.3 , are likely homologous to human and mouse GJB2 . During embryogenesis, zebrafish cx27.5 was rarely expressed at 1.5–3 h post-fertilization (hpf), but a relatively high level of cx27.5 expression was detected from 6 to 96 hpf. However, zebrafish cx30.3 transcripts were hardly detected until 9 hpf. The temporal experiment was conducted in whole larvae. Both cx27.5 and cx30.3 transcripts were revealed significantly in the inner ear by reverse transcription polymerase chain reaction (RT-PCR) and whole-mount in situ hybridization (WISH). In the HeLa cell model, we found that zebrafish Cx27.5 was distributed intracellularly in the cytoplasm, whereas Cx30.3 was localized in the plasma membrane of HeLa cells stably expressing Cx proteins. The expression pattern of zebrafish Cx30.3 in HeLa cells was more similar to that of cells expressing human CX26 than Cx27.5. In addition, we found that Cx30.3 was localized in the cell membrane of hair cells within the inner ear by immunohistochemistry (IHC), suggesting that zebrafish cx30.3 might play an essential role in the development of the inner ear, in the same manner as human GJB2 . We then performed morpholino knockdown studies in zebrafish embryos to elucidate the physiological functions of Cx30.3. The zebrafish cx30.3 morphants exhibited wild-type-like and heart edema phenotypes with smaller inner ears at 72 hpf. Based on these results, we suggest that the zebrafish Cx30.3 and mammalian CX26 may play alike roles in the inner ear. Thus, zebrafish can potentially serve as a model for studying hearing loss disorders that result from human CX26 mutations.

  • mutation r184q of Connexin 26 in hearing loss patients has a dominant negative effect on Connexin 26 and Connexin 30
    European Journal of Human Genetics, 2010
    Co-Authors: Chingchyuan Su, Shuanyow Li, Maochang Su, Weichi Chen, Jiannjou Yang
    Abstract:

    Hearing impairment is the most common sensory disorder worldwide. In a recent study, the authors have shown that a heterozygous missense mutation, p.R184Q, in the Connexin 26 (Cx26) is causally related to hearing loss. However, the functional change in the Cx26R184Q mutant remains unknown. This study compared the intracellular distribution and assembly of mutant Cx26R184Q with that of the wild-type (WT) Cx26 and Cx30WT in tet-on HeLa cells and the effect that the mutant protein had on those cells. Fluorescent localization assay of WT Cx26 showed the typical punctuate pattern of gap junction channel between neighboring expression cells. Conversely, the p.R184Q missense mutation resulted in accumulation of the Cx26 mutant protein in the Golgi apparatus rather than in the cytoplasmic membrane. Cx26R184Q coexpressed with either Cx26WT or Cx30WT showed perinuclear localization by bidirectional tet-on expression system, suggesting the impairment of the ability of both WT proteins to intracellular trafficking and targeting to the plasma membrane. Therefore, we proposed that Cx26R184Q has a dominant-negative effect on the function of WT Cx26 and Cx30.

  • novel expression patterns of Connexin 30 3 in adult rat cochlea
    Hearing Research, 2010
    Co-Authors: Wenhung Wang, Jiannjou Yang, Jentsung Yang, Shuanyow Li
    Abstract:

    Abstract Mutations of the GJB4 gene, encoding Connexin 30.3 (CX30.3), are associated with skin disorders. Recently, this gene was also detected in deaf individuals without skin disorders. However, the functional roles of CX30.3 in the cochlea remain unclear. A primary step toward understanding the role of CX30.3 in hearing and its dysfunction is the documentation of its cellular and sub-cellular locations within the cochlea. In the present study, we located and determined the cellular expression of Cx30.3 within the rat cochlea by using a polyclonal anti-Cx30.3 antibody. Expression of the Cx30.3 protein was detected in the spiral limbus, spiral ligament, spiral ganglion, and stria vascularis by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR) analyses. Our results indicate the presence and localization of Cx30.3 in the rat cochlea. Knowledge of the spatial distribution of Cx30.3 will provide important insights into its role in the cochleae and normal auditory function.

Ulrike Pannasch - One of the best experts on this subject based on the ideXlab platform.

  • Astroglial Cx30 sustains neuronal population bursts independently of gap‐junction mediated biochemical coupling
    Glia, 2019
    Co-Authors: Ulrike Pannasch, Pascal Ezan, Elena Dossi, Nathalie Rouach
    Abstract:

    : Astroglial networks mediated by gap junction channels contribute to neurotransmission and promote neuronal coordination. Connexin 30, one of the two main astroglial gap junction forming protein, alters at the behavioral level the reactivity of mice to novel environment and at the synaptic level excitatory transmission. However, the role and function of Cx30 at the neuronal network level remain unclear. We thus investigated whether Cx30 regulates neuronal population bursts and associated convulsive behavior. We found in vivo that Cx30 is upregulated by kainate-induced seizures and that it regulates in turn the severity of associated behavioral seizures. Using electrophysiology ex vivo, we report that Cx30 regulates aberrant network activity via control of astroglial glutamate clearance independently of gap-junction mediated biochemical coupling. Altogether, our results indicate that astroglial Cx30 is an important player in orchestrating neuronal network activity.

  • Connexin 30 controls astroglial polarization during postnatal brain development
    Development, 2018
    Co-Authors: Gregory Ghezali, Charlesfelix Calvo, Laureelise Pillet, Flora Llense, Pascal Ezan, Ulrike Pannasch, Alexispierre Bemelmans, Sandrine Etienne Manneville
    Abstract:

    ABSTRACT Astrocytes undergo intense morphological maturation during development, changing from individual sparsely branched cells to polarized and tremendously ramified cells. Connexin 30, an astroglial gap-junction channel-forming protein expressed postnatally, regulates in situ the extension and ramification of astroglial processes. However, the involvement of Connexin 30 in astroglial polarization, which is known to control cell morphology, remains unexplored. We found that Connexin 30, independently of gap-junction-mediated intercellular biochemical coupling, alters the orientation of astrocyte protrusion, centrosome and Golgi apparatus during polarized migration in an in vitro wound-healing assay. Connexin 30 sets the orientation of astroglial motile protrusions via modulation of the laminin/β1 integrin/Cdc42 polarity pathway. Connexin 30 indeed reduces laminin levels, inhibits the redistribution of the β1-integrin extracellular matrix receptors, and inhibits the recruitment and activation of the small Rho GTPase Cdc42 at the leading edge of migrating astrocytes. In vivo , Connexin 30, the expression of which is developmentally regulated, also contributes to the establishment of hippocampal astrocyte polarity during postnatal maturation. This study thus reveals that Connexin 30 controls astroglial polarity during development.

  • Astroglial networks promote neuronal coordination
    Science Signaling, 2016
    Co-Authors: Oana Chever, Ulrike Pannasch, Elena Dossi, Mickael Derangeon, Nathalie Rouach
    Abstract:

    Astrocytes interact with neurons to regulate network activity. Although the gap junction subunits Connexin 30 and Connexin 43 mediate the formation of extensive astroglial networks that cover large functional neuronal territories, their role in neuronal synchronization remains unknown. Using Connexin 30– and Connexin 43–deficient mice, we showed that astroglial networks promoted sustained population bursts in hippocampal slices by setting the basal active state of neurons. Astroglial networks limited excessive neuronal depolarization induced by spontaneous synaptic activity, increased neuronal release probability, and favored the recruitment of neurons during bursting, thus promoting the coordinated activation of neuronal networks. In vivo, this sustained neuronal coordination translated into increased severity of acutely evoked epileptiform events and convulsive behavior. These results revealed that Connexin-mediated astroglial networks synchronize bursting of neuronal assemblies, which can exacerbate pathological network activity and associated behavior. Our data thus provide molecular and biophysical evidence predicting selective astroglial gap junction inhibitors as anticonvulsive drugs.

  • Connexin 30 sets synaptic strength by controlling astroglial synapse invasion
    Nature Neuroscience, 2014
    Co-Authors: Gregory Ghezali, Ulrike Pannasch, Dominik Freche, Glenn Dallerac, Carole Escartin
    Abstract:

    Astrocytes provide essential support for and modulate synaptic transmission between neurons. Here the authors show that non-channel functions of Connexin 30, a gap-junction subunit, control the synaptic coverage of astroglial processes and regulate glutamate clearance, synaptic strength and memory function.

  • Astroglial networks scale synaptic activity and plasticity
    Proceedings of the National Academy of Sciences of the United States of America, 2011
    Co-Authors: Ulrike Pannasch, Pascal Ezan, Christian Giaume, Lydia Vargova, Jürgen Reingruber, David Holcman, Eva Syková, Nathalie Rouach
    Abstract:

    Astrocytes dynamically interact with neurons to regulate synaptic transmission. Although the gap junction proteins Connexin 30 (Cx30) and Connexin 43 (Cx43) mediate the extensive network organization of astrocytes, their role in synaptic physiology is unknown. Here we show, by inactivating Cx30 and Cx43 genes, that astroglial networks tone down hippocampal synaptic transmission in CA1 pyramidal neurons. Gap junctional networking facilitates extracellular glutamate and potassium removal during synaptic activity through modulation of astroglial clearance rate and extracellular space volume. This regulation limits neuronal excitability, release probability, and insertion of postsynaptic AMPA receptors, silencing synapses. By controlling synaptic strength, Connexins play an important role in synaptic plasticity. Altogether, these results establish Connexins as critical proteins for extracellular homeostasis, important for the formation of functional synapses.