The role of CaMKIV in the neurotrophin -induced priming effect and the characterization/regeneration of ES-derived motor neurons.
Item
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Title
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The role of CaMKIV in the neurotrophin -induced priming effect and the characterization/regeneration of ES-derived motor neurons.
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Identifier
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AAI3169984
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identifier
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3169984
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Creator
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Spencer, Tim.
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Contributor
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Adviser: Marie T. Filbin
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Date
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2005
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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 | Biology, Molecular | Biology, Cell
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Abstract
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The lack of axonal regeneration observed in the adult mammalian central nervous system (CNS) is due, in part, to the presence of the myelin-associated inhibitors, such as myelin-associated glycoprotein (MAG). The inhibition induced by these molecules, or by myelin in general, can be blocked, however, via artificial (dibutyryl-cAMP) or signaling-induced (neurotrophin-treated) elevation of intracellular cAMP and modulation of the PKA and ERK pathways. We have previously shown that these effects are dependent on the activation of the cellular transcription factor, the cAMP response-element binding protein (CREB). Calcium/calmodulin-dependant kinase IV (CaMKIV) has been shown to act as a modulator of CREB activity and therefore, we set out to elucidate what role, if any, CaMK plays in the neurotrophin-induced block of MAG-mediated inhibition of neurite outgrowth. Here, we show that blocking CaMK with the pharmacological inhibitor KN-62 can abrogate the BDNF-induced phosphorylation of CREB as well as the reversal of MAG-mediated inhibition of neurite outgrowth from cerebellar (CN) and dorsal root ganglion (DRG) neurons. In contrast, we find that KN-62 cannot block phosphorylation of CREB or the MAG-mediated inhibition in neurons treated with dibutyryl-cAMP.;In order to verify and attribute these findings specifically to the CaMKIV moiety, we generated adenoviral constructs containing constitutively-active and kinase-dead mutant forms of CaMKIV and infected primary neurons in vitro prior to exposure to MAG-expressing CHO cells or purified myelin. Our findings indicate that CaMKIV is a downstream effector in the BDNF-induced priming pathway. Furthermore, we show that blocking CaMK signaling has no effect on the elevation of endogenous cAMP levels which occurs in response to priming with BDNF suggesting that CaMKIV is not upstream from cAMP elevation and PKA activation, but rather constitutes a separate and parallel signaling pathway, leading to CREB phosphorylation and activation of transcription. Further evidence suggests that calcium influx from intracellular stores may be responsible for this induction of CaMKIV and its subsequent activity.
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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.
