Novel effects of serotonin 1A receptor-mediated signaling through MAP kinase.
Item
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Title
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Novel effects of serotonin 1A receptor-mediated signaling through MAP kinase.
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Identifier
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AAI3144073
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identifier
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3144073
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Creator
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Adayev, Tatyana.
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Contributor
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Adviser: Probal Banerjee
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Date
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2004
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Neuroscience
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Abstract
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An ischemic stroke is associated with a massive depolarization of the brain tissue, which is followed by an onset of apoptosic changes as a result of excitotoxicity and/or due to reoxygenation of the tissue. The hippocampal regions have been repeatedly reported to be a common site of the neuronal loss independent of the exact location of the ischemic core. Serotonin 1A receptors (5-HT1A-R), which are particularly abundant in hippocampal regions, exhibit some neuroptotective properties when activated by agonists. Until recently, the possibility of using the 5-HT1A-R agonists as alternative treatment of ischemic stroke patients was overlooked. Overall neuroprotection offered by the agonists of the 5-HT1A-R is a collective effect of receptor-mediated signaling through multiple pathways. In this study, we chose as a model a mouse hippocampus-derived cell line HN2--5, which expresses 5-HT1A-R, and is devoid of expression of voltage-gated Calcium ion channels. Equipped with this model, we studied the role of 5-HT 1A-R in stimulating Ca-channel-independent pathways, which block apoptosis. Prolonged agonist stimulation of the 5-HT1A-R results in a phosphoinositide tris-phosphate (PI-3K) independent, slow and persistent MAPK activation that has been shown to be a part of a neuroprotective pathway leading to inhibition caspase-3 processing. This neuroprotection is equally effective against anoxia- and H2O2-induced apoptosis, suggesting that a general anti-apoptotic mechanism is mediated by the 5-HT1A-R agonists in suppressing the apoptotic machinery downstream of the mitochondria. This neuroprotection is dependent on PL-Cbeta, ERK 1/2 and PKCalpha. The ERK 1/2 enzymes play a key role in mediating anti-apoptotic signaling via regulation of PKCalpha activity. Detergent soluble cellular membrane fractions of agonist-stimulated HN2--5 cells showed ERK 1/2 dependent increase in phospho-PKCalpha (pSer657, and pThr638), which is indicative of the activation of PKCalpha. Membrane associated phospho-PKCalpha profile closely followed the phospho-ERK 1/2 profile and co-immunoprecipitated with ERK-2 from membrane-bound but not cytosolic fractions of the cell. This study presents a novel mode of regulation of caspase-3 by MAPK through its association with PKCalpha. It is the first documented report on co-immunoprecipitation of ERK and PKCalpha kinases, suggestive of direct phosphorylation of PKCalpha turn motif (Thr638) by the ERKs.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
