Browsing by Author "Zamorano, Pedro"

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    An Early Disturbance in Serotonergic Neurotransmission Contributes to the Onset of Parkinsonian Phenotypes in Drosophila melanogaster
    (MDPI, 2022) Zárate Canales, Rafaella Victoria; Hidalgo, Sergio; Navarro, Nicole; Molina Mateo, Daniela Francisca; Arancibia, Duxan; Rojo Cortés, Francisca Rayén; Oliva, Carlos; Andrés Coke, María Estela; Zamorano, Pedro; Campusano Astorga, Jorge Mauricio
    Parkinson's disease (PD) is a neurodegenerative disease characterized by motor symptoms and dopaminergic cell loss. A pre-symptomatic phase characterized by non-motor symptoms precedes the onset of motor alterations. Two recent PET studies in human carriers of mutations associated with familial PD demonstrate an early serotonergic commitment-alteration in SERT binding-before any dopaminergic or motor dysfunction, that is, at putative PD pre-symptomatic stages. These findings support the hypothesis that early alterations in the serotonergic system could contribute to the progression of PD, an idea difficult to be tested in humans. Here, we study some components of the serotonergic system during the pre-symptomatic phase in a well-characterized Drosophila PD model, Pink1(B9) mutant flies. We detected lower brain serotonin content in Pink1(B9) flies, accompanied by reduced activity of SERT before the onset of motor dysfunctions. We also explored the consequences of a brief early manipulation of the serotonergic system in the development of motor symptoms later in aged animals. Feeding young Pink1(B9) flies with fluoxetine, a SERT blocker, prevents the loss of dopaminergic neurons and ameliorates motor impairment observed in aged mutant flies. Surprisingly, the same pharmacological manipulation in young control flies results in aged animals exhibiting a PD-like phenotype. Our findings support that an early dysfunction in the serotonergic system precedes and contributes to the onset of the Parkinsonian phenotype in Drosophila.
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    Exo70 intracellular redistribution after repeated mild traumatic brain injury
    (2021) Lira Mendieta, Matías Sebastián; Zamorano, Pedro; Cerpa Nebott, Waldo Francisco
    Abstract Background Exo70 is a subunit of the greater exocyst complex, a collection of proteins that oversees cellular membrane addition and polarized exocytosis by acting as a tethering intermediate between the plasma membrane and newly synthesized secretory vesicles. Although Exo70 function has been implicated in several developmental events including cytokinesis and the establishment of cell polarity, its role in neuropathologies is poorly understood. On the other hand, traumatic brain injury is the result of mechanical external force including contusion, fast acceleration, and expansive waves that produce temporal or permanent cognitive damage and triggers physical and psychosocial alterations including headache, memory problems, attention deficits, difficulty thinking, mood swings, and frustration. Traumatic brain injury is a critical health problem on a global scale, constituting a major cause of deaths and disability among young adults. Trauma-related cellular damage includes redistribution of N-methyl-D-aspartate receptors outside of the synaptic compartment triggering detrimental effects to neurons. The exocyst has been related to glutamate receptor constitutive trafficking/delivery towards synapse as well. This work examines whether the exocyst complex subunit Exo70 participates in traumatic brain injury and if it is redistributed among subcellular compartments Results Our analysis shows that Exo70 expression is not altered upon injury induction. By using subcellular fractionation, we determined that Exo70 is redistributed from microsomes fraction into the synaptic compartment after brain trauma. In the synaptic compartment, we also show that the exocyst complex assembly and its interaction with GluN2B are increased. Finally, we show that the Exo70 pool that is redistributed comes from the plasma membrane. Conclusions The present findings position Exo70 in the group of proteins that could modulate GluN2B synaptic availability in acute neuropathology like a traumatic brain injury. By acting as a nucleator factor, Exo70 is capable of redirecting the ensembled complex into the synapse. We suggest that this redistribution is part of a compensatory mechanism by which Exo70 is able to maintain GluN2B partially on synapses. Hence, reducing the detrimental effects associated with TBI pathophysiology.
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    Exo70 protects against memory and synaptic impairments following mild traumatic brain injury
    (2023) Lira, Matias; Abarca, Jorge; Mira, Rodrigo G.; Zamorano, Pedro; Cerpa Nebott, Waldo Francisco
    Mild traumatic brain injury (mTBI) is damage to the brain due to external forces. It is the most frequent form of brain trauma and a leading cause of disability in young adults. Hippocampal glutamatergic transmission and synaptic plasticity are impaired after mTBI, and NMDA receptors play critical in these functions. The Exocyst is a vesicle tethering complex implicated in the trafficking of glutamate receptors. We have previously shown that Exo70, a critical exocyst's subunit, redistributes in the synapse and increases its interaction with GluN2B in response to mTBI, suggesting a role in the distribution of the GluN2B subunit of NMDARs from synaptic to extrasynaptic membranes. We tested whether Exo70 could prevent NMDAR depletion from the synapse and limit mTBI pathology. To this end, we used a modified Maryland's model of mTBI in mice overexpressing Exo70 in CA1 pyramidal neurons through a lentiviral vector transduction. We showed that after mTBI, the overexpression of Exo70 prevented the cognitive impairment observed in mice infected with a control vector using the Morris' water maze paradigm. Following these findings, mice overexpressing Exo70 showed basal and NMDAR-dependent hippocampal synaptic transmission comparable to sham animals, preventing the deterioration induced by mTBI. Long-term potentiation, abundant synaptic GluN2B-containing NMDARs, and downstream signaling effectors showed that Exo70 overexpression prevented the mTBI-induced alterations. Our findings revealed a crucial role of Exo70 in NMDAR trafficking to the synapse and suggested that the Exocyst complex may be a critical component of the basal machinery that regulates NMDAR distribution in health and disease.
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    Glutamatergic Receptor Trafficking and Delivery: Role of the Exocyst Complex
    (NLM (Medline), 2020) Lira, Matías; Mira, Rodrigo G.; Cerpa Nebott Waldo Francisco; Carvajal, Francisco J.; Inestrosa, Nibaldo C.; Zamorano, Pedro
    Cells comprise several intracellular membrane compartments that allow them to function properly. One of these functions is cargo movement, typically proteins and membranes within cells. These cargoes ride microtubules through vesicles from Golgi and recycling endosomes to the plasma membrane in order to be delivered and exocytosed. In neurons, synaptic functions employ this cargo trafficking to maintain inter-neuronal communication optimally. One of the complexes that oversee vesicle trafficking and tethering is the exocyst. The exocyst is a protein complex containing eight subunits first identified in yeast and then characterized in multicellular organisms. This complex is related to several cellular processes, including cellular growth, division, migration, and morphogenesis, among others. It has been associated with glutamatergic receptor trafficking and tethering into the synapse, providing the molecular machinery to deliver receptor-containing vesicles into the plasma membrane in a constitutive manner. In this review, we discuss the evidence so far published regarding receptor trafficking and the exocyst complex in both basal and stimulated levels, comparing constitutive trafficking and long-term potentiation-related trafficking.
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    Pathogenicity of lupus anti-ribosomal P antibodies : Role of cross-reacting neuronal surface P antigen in glutamatergic transmission and plasticity in a mouse model
    (2015) Segovia Miranda, Fabián; Serrano, Felipe; Dyrda, Agnieszka; Ampuero, Estibaliz; Retamal, Claudio; Bravo Zehnder, Marcela; Parodi, Jorge; Zamorano, Pedro; Valenzuela, David; Massardo Vega, Loreto; Van Zundert, Brigitte; Inestrosa Cantín, Nibaldo; González Alfonso
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    The metabolite p-cresol impairs dendritic development, synaptogenesis, and synapse function in hippocampal neurons: Implications for autism spectrum disorder
    (2022) Guzmán Salas, Sheyla; Weber, André; Malci, Ayse; Lin, Xiao; Herrera Molina, Rodrigo; Cerpa Nebott, Waldo Francisco; Dorador, Cristina; Signorelli, Janetti; Zamorano, Pedro
    Autism spectrum disorder (ASD) is a heterogeneous neurodevelopment disorder resulting from different etiological factors, both genetic and/or environmental. These factors can lead to abnormal neuronal development on dendrite and synaptic function at the central nervous system. Recent studies have shown that a subset of ASD patients display increased circulation levels of the tyrosine metabolite, p-cresol, related to chronic intestinal disorders because of dysbiosis of the intestinal microbiota. In particular, abnormal presence of intestinal Clostridium sp. has been linked to high levels of p-cresol in ASD children younger than 8 years. However, the role of p-cresol during development of the central nervous system is unknown. Here, we evaluated in vitro the effect of p-cresol on neurite outgrowth in N2a and PC12 cell lines and dendritic morphology, synaptic density, neuronal activity, and calcium responses in primary rat hippocampal neurons. p-cresol inhibits neural differentiation and neurites outgrowth in N2a and PC12 neuronal cell lines. In hippocampal neuronal cultures, Sholl's analysis shows a decrease in the dendritic arborization of neurons treated with p-cresol. Synaptic density analyzed with the synaptic markers Piccolo and Shank2 is diminished in hippocampal neurons treated with p-cresol. Electrically evoked intracellular calcium rise was drastically, but reversely, blocked by p-cresol, whereas that spontaneous neuronal activity was severely affected by early addition of the metabolite. These findings show that p-cresol alters dendrite development, synaptogenesis, and synapse function of neurons in culture, therefore, neuronal alterations occurring in ASD children may be related to this metabolite and dysbiosis of the intestinal microbiota.
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    Trypanosoma cruzi Infection Induces Pannexin-1 Channel Opening in Cardiac Myocytes
    (2018) Barria, Ivan; Guiza, Juan; Cifuentes, Fredi; Zamorano, Pedro; Sáez, Juan Carlos; Gonzalez, Jorge; Vega, Jose L.