Browsing by Author "Barría, MI"

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    The human prion octarepeat fragment prevents and reverses the inhibitory action of copper in the P2X4 receptor without modifying the zinc action
    (2003) Lorca, RA; Chacón, M; Barría, MI; Inestrosa, NC; Huidobro-Toro, JP
    Human prion protein fragments (PrP60-67 or PrP59-91) prevented and reversed the inhibition elicited by 5 mum copper on the P2X(4) receptor expressed in Xenopus laevis oocytes. A 60-s pre-application of 5 muM copper caused a 69.2 +/- 2.6% inhibition of the 10 muM adenosine triphosphate (ATP)-evoked currents, an effect that was prevented by mixing 5 muM copper with 0.01-10 muM of the PrP fragments 1-min prior to application. This interaction was selective, as PrP59-91 did not alter the facilitatory action of zinc. The EC50 of PrP60-67 and PrP59-91 for the reduction of the copper inhibition were 4.6 +/- 1 and 1.3 +/- 0.4 muM, respectively. A synthetic PrP59-91 variant in which all four His were replaced by Ala was inactive. However, the replacement of Trp in each of the four putative copper-binding domains by Ala slightly decreased its potency. Furthermore, the application of 10 muM PrP59-91 reversed the copper-evoked inhibition, restoring the ATP concentration curve to the same level as the non-inhibited state. Fragment 139-157 of betaA4 amyloid precursor protein also prevented the action of copper; its EC50 was 1.6 +/- 0.1 muM; the metal chelator penicillamine was equipotent with PrP60-67, but carnosine was significantly less potent. Our findings highlight the role of PrP in copper homeostasis and hint at its possible role as a modulator of synapses regulated by this trace metal.
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    The N-terminal copper-binding domain of the amyloid precursor protein protects against Cu2+ neurotoxicity in vivo
    (2004) Cerpa, WF; Barría, MI; Chacón, MA; Suazo, M; González, M; Opazo, C; Bush, AI; Inestrosa, NC
    The amyloid precursor protein (APP) contains a Cu binding domain (CuBD) localized between amino acids 135 and 156 (APP(135-156)), which can reduce Cu2+ to Cu1+ in vitro. The physiological function of this APP domain has not yet being established; nevertheless several studies support the notion that the CuBD of APP is involved in Cu homeostasis. We used APP synthetic peptides to evaluate their protective properties against Cu2+ neurotoxicity in a bilateral intra-hippocampal injection model. We found that human APP135-156 protects against Cu2+-induced neurotoxic effects, such as, impairment of spatial memory, neuronal cell loss, and astrogliosis. APP135-156 lacking two histidine residues showed protection against Cu2+; however, APP135-156 mutated in cysteine 144, a key residue in the reduction of Cu2+ to Cu1+, did not protect against Cu2+ neurotoxicity. In accordance with recent reports, the CuBD of the Caenorhabditis elegans, APL-1 protected against Cu2+ neurotoxicity in vivo. We also found that Cu2+ neurotoxicity is associated with an increase in nitrotyrosine immunofluorescence as well as with a decrease in Cu2+ uptake. The CuBD of APP therefore may play a role in the detoxification of brain Cu.
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    Wnt signaling involvement in β-amyloid-dependent neurodegeneration
    (2002) Inestrosa, NC; De Ferrari, GV; Garrido, JL; Alvarez, A; Olivares, GH; Barría, MI; Bronfman, M; Chacón, MA
    Alzheimer's disease (AD) is a progressive dementia paralleled by selective neuronal death, which is probably caused by the cytotoxic effects of the amyloid-p peptide (Abeta). We have observed that Abeta-dependent neurotoxicity induces a loss of function of Wnt signaling components and that activation of this signaling cascade prevent such cytotoxic effects. Therefore we propose that compounds which mimic this signaling cascade may be candidates for therapeutic intervention in Alzheimer's patients. (C) 2002 Elsevier Science Ltd. All rights reserved.