Browsing by Author "Codocedo, Juan F."

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    Posttranslational Modifications Regulate the Postsynaptic Localization of PSD-95
    (2017) Vallejo, Daniela; Codocedo, Juan F.; Inestrosa Cantín, Nibaldo
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    Reactive Oxygen Species Potentiate the P2X(2) Receptor Activity through Intracellular Cys(430)
    (SOC NEUROSCIENCE, 2009) Coddou, Claudio; Codocedo, Juan F.; Li, Shuo; Lillo, Juan G.; Acuna Castillo, Claudio; Bull, Paulina; Stojilkovic, Stanko S.; Huidobro Toro, J. Pablo
    P2X receptor channels (P2XRs) are allosterically modulated by several compounds, mainly acting at the ectodomain of the receptor. Like copper, mercury, a metal that induces oxidative stress in cells, also stimulates the activity of P2X(2)R and inhibits the activity of P2X(4)R. However, the mercury modulation is not related to the extracellular residues critical for copper modulation. To identify the site(s) for mercury action, we generated two chimeras using the full size P2X(2) subunit, termed P2X(2a), and a splice variant lacking a 69 residue segment in the C terminal, termed P2X(2b), as the donors for intracellular and transmembrane segments and the P2X(4) subunit as the donor for ectodomain segment of chimeras. The potentiating effect of mercury on ATP-induced current was preserved in Xenopus oocytes expressing P2X(4/2a) chimera but was absent in oocytes expressing P2X(4/2b) chimera. Site-directed mutagenesis experiments revealed that the Cys(430) residue mediates effects of mercury on the P2X(2a)R activity. Because mercury could act as an oxidative stress inducer, we also tested whether hydrogen peroxide (H2O2) and mitochondrial stress inducers myxothiazol and rotenone mimicked mercury effects. These experiments, done in both oocytes and human embryonic kidney HEK293 cells, revealed that these compounds potentiated the ATP-evoked P2X(2a)R and P2X(4/2a)R currents but not P2X(2b)R and P2X(2a)-C430A and P2X(2a)-C430S mutant currents, whereas antioxidants dithiothreitrol and N-acetylcysteine prevented the H2O2 potentiation. Alkylation of Cys(430) residue with methylmethane-thiosulfonate also abolished the mercury and H2O2 potentiation. Altogether, these results are consistent with the hypothesis that the Cys(430) residue is an intracellular P2X(2a)R redox sensor.
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    SIRT1 Regulates Dendritic Development in Hippocampal Neurons
    (2012) Codocedo, Juan F.; Allard, Claudio; Godoy, Juan A.; Varela-Nallar, Lorena; Inestrosa, Nibaldo C.
    Dendritic arborization is required for proper neuronal connectivity. SIRT1, a NAD+ dependent histone deacetylase, has been associated to ageing and longevity, which in neurons is linked to neuronal differentiation and neuroprotection. In the present study, the role of SIRT1 in dendritic development was evaluated in cultured hippocampal neurons which were transfected at 3 days in vitro with a construct coding for SIRT1 or for the dominant negative SIRT1H363Y, which lacks the catalytic activity. Neurons overexpressing SIRT1 showed an increased dendritic arborization, while neurons overexpressing SIRT1H363Y showed a reduction in dendritic arbor complexity. The effect of SIRT1 was mimicked by treatment with resveratrol, a well known activator of SIRT1, which has no effect in neurons overexpressing SIRT1H363Y indicating that the effect of resveratrol was specifically mediated by SIRT1. Moreover, hippocampal neurons overexpressing SIRT1 were resistant to dendritic dystrophy induced by A beta aggregates, an effect that was dependent on the deacetylase activity of SIRT1. Our findings indicate that SIRT1 plays a role in the development and maintenance of dendritic branching in hippocampal neurons, and suggest that these effects are mediated by the ROCK signaling pathway.
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    Wnt-5a-regulated miR-101b controls COX2 expression in hippocampal neurons
    (2016) Codocedo, Juan F.; Inestrosa Cantín, Nibaldo
    Abstract Background Wnt-5a is a member of the WNT family of secreted lipoglycoproteins, whose expression increases during development; moreover, Wnt-5a plays a key role in synaptic structure and function in the adult nervous system. However, the mechanism underlying these effects is still elusive. MicroRNAs (miRNAs) are a family of small non-coding RNAs that control the gene expression of their targets through hybridization with complementary sequences in the 3′ UTR, thereby inhibiting the translation of the target proteins. Several evidences indicate that the miRNAs are actively involved in the regulation of neuronal function. Results In the present study, we examined whether Wnt-5a modulates the levels of miRNAs in hippocampal neurons. Using PCR arrays, we identified a set of miRNAs that respond to Wnt-5a treatment. One of the most affected miRNAs was miR-101b, which targets cyclooxygenase-2 (COX2), an inducible enzyme that converts arachidonic acid to prostanoids, and has been involved in the injury/inflammatory response, and more recently in neuronal plasticity. Consistent with the Wnt-5a regulation of miR-101b, this Wnt ligand regulates COX2 expression in a time-dependent manner in cultured hippocampal neurons. Conclusion The biological processes induced by Wnt-5a in hippocampal neurons, involve the regulation of several miRNAs including miR-101b, which has the capacity to regulate several targets, including COX-2 in the central nervous system.
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    Wnt-related SynGAP1 is a neuroprotective factor of glutamatergic synapses against Aβ oligomers
    (2015) Codocedo, Juan F.; Montecinos Oliva, Carla; Inestrosa Cantín, Nibaldo