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- All Subjects: Molecular Biology
Description
Intermittent social defeat stress induces cross-sensitization to psychostimulants and escalation of drug self-administration. These behaviors could result from the stress-induced neuroadaptation in the mesocorticolimbic dopamine circuit. Brain-derived neurotrophic factor (BDNF) in the ventral tegmental area (VTA) is persistently elevated after social defeat stress, and may contribute to the stress-induced neuroadaptation in the mesocorticolimbic dopamine circuit. BDNF modulates synaptic plasticity, and facilitates stress- and drug-induced neuroadaptations in the mesocorticolimbic system. The present research examined the role of mesolimbic BDNF signaling in social defeat stress-induced cross-sensitization to psychostimulants and the escalation of cocaine self-administration in rats. We measured drug taking behavior with the acquisition, progressive ratio, and binge paradigms during self-administration. With BDNF overexpression in the ventral tegmental area (VTA), single social defeat stress-induced cross-sensitization to amphetamine (AMPH) was significantly potentiated. VTA-BDNF overexpression also facilitates acquisition of cocaine self-administration, and a positive correlation between the level of VTA BDNF and drug intake during 12 hour binge was observed. We also found significant increase of DeltaFosB expression in the nucleus accumbens (NAc), the projection area of the VTA, in rats received intra-VTA BDNF overexpression. We therefore examined whether BDNF signaling in the NAc is important for social defeat stress-induced cross-sensitization by knockdown of the receptor of BDNF (neurotrophin tyrosine kinase receptor type 2, TrkB) there. NAc TrkB knockdown prevented social defeat stress-induced cross-sensitization to psychostimulant. Also social defeat stress-induced increase of DeltaFosB in the NAc was prevented by TrkB knockdown. Several other factors up-regulated by stress, such as the GluA1 subunit of Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor and BDNF in the VTA were also prevented. We conclude that BDNF signaling in the VTA increases social defeat stress-induced vulnerability to psychostimulants, manifested as potentiated cross-sensitization/sensitization to AMPH and escalation of cocaine self-administration. Also BDNF signaling in the NAc is necessary for the stress-induced neuroadaptation and behavioral sensitization to psychostimulants. Therefore, TrkB in the NAc could be a therapeutic target to prevent stress-induced vulnerability to drugs of abuse in the future. DeltaFosB in the NAc shell could be a neural substrate underlying persistent cross-sensitization and augmented cocaine self-administration induced by social defeat stress.
ContributorsWang, Junshi (Author) / Hammer, Ronald (Thesis advisor) / Feuerstein, Burt (Committee member) / Nikulina, Ella (Committee member) / Neisewander, Janet (Committee member) / Arizona State University (Publisher)
Created2013
Description
Cells live in complex environments and must be able to adapt to environmental changes in order to survive. The ability of a cell to survive and thrive in a changing environment depends largely on its ability to receive and respond to extracellular signals. Initiating with receptors, signal transduction cascades begin translating extracellular signals into intracellular messages. Such signaling cascades are responsible for the regulation of cellular metabolism, cell growth, cell movement, transcription, translation, proliferation and differentiation. This dissertation seeks to dissect and examine critical signaling pathways involved in the regulation of proliferation in neural stem cells (Chapter 2) and the regulation of Glioblastoma Multiforme pathogenesis (GBM; Chapter 3). In Chapter 2 of this dissertation, we hypothesize that the mTOR signaling pathway plays a significant role in the determination of neural stem cell proliferation given its control of cell growth, metabolism and survival. We describe the effect of inhibition of mTOR signaling on neural stem cell proliferation using animal models of aging. Our results show that the molecular method of targeted inhibition may result in differential effects on neural stem cell proliferation as the use of rapamycin significantly reduced proliferation while the use of metformin did not. Abnormal signaling cascades resulting in unrestricted proliferation may lead to the development of brain cancer, such as GBM. In Chapter 3 of this dissertation, we hypothesize that the inhibition of the protein kinase, aPKCλ results in halted GBM progression (invasion and proliferation) due to its central location in multiple signaling cascades. Using in-vitro and in-vivo models, we show that aPKCλ functions as a critical node in GBM signaling as both cell-autonomous and non-cell-autonomous signaling converge on aPKCλ resulting in pathogenic downstream effects. This dissertation aims to uncover the molecular mechanisms involved in cell signaling pathways which are responsible for critical cellular effects such as proliferation, invasion and transcriptional regulation.
ContributorsKusne, Yael (Author) / Sanai, Nader (Thesis advisor) / Neisewander, Janet (Thesis advisor) / Tran, Nhan (Committee member) / Hammer, Ronald (Committee member) / Narayanan, Vinodh (Committee member) / Shapiro, Joan (Committee member) / Arizona State University (Publisher)
Created2014
Description
The RASopathies are a collection of developmental diseases caused by germline mutations in components of the RAS/MAPK signaling pathway and is one of the world’s most common set of genetic diseases. A majority of these mutations result in an upregulation of RAS/MAPK signaling and cause a variety of both physical and neurological symptoms. Neurodevelopmental symptoms of the RASopathies include cognitive and motor delays, learning and intellectual disabilities, and various behavioral problems. Recent noninvasive imaging studies have detected widespread abnormalities within white matter tracts in the brains of RASopathy patients. These abnormalities are believed to be indicative of underlying connectivity deficits and a possible source of the behavioral and cognitive deficits. To evaluate these long-range connectivity and behavioral issues in a cell-autonomous manner, MEK1 loss- and gain-of-function (LoF and GoF) mutations were induced solely in the cortical glutamatergic neurons using a Nex:Cre mouse model. Layer autonomous effects of the cortex were also tested in the GoF mouse using a layer 5 specific Rbp4:Cre mouse. Immunohistochemical analysis showed that activated ERK1/2 (P-ERK1/2) was expressed in high levels in the axonal compartments and reduced levels in the soma when compared to control mice. Axonal tract tracing using a lipophilic dye and an adeno-associated viral (AAV) tract tracing vector, identified significant corticospinal tract (CST) elongation deficits in the LoF and GoF Nex:Cre mouse and in the GoF Rbp4:Cre mouse. AAV tract tracing was further used to identify significant deficits in axonal innervation of the contralateral cortex, the dorsal striatum, and the hind brain of the Nex:Cre GoF mouse and the contralateral cortex and dorsal striatum of the Rbp4:Cre mouse. Behavioral testing of the Nex:Cre GoF mouse indicated deficits in motor learning acquisition while the Rbp4:Cre GoF mouse showed no failure to acquire motor skills as tested. Analysis of the expression levels of the immediate early gene ARC in Nex:Cre and Rbp4:Cre mice showed a specific reduction in a cell- and layer-autonomous manner. These findings suggest that hyperactivation of the RAS/MAPK pathway in cortical glutamatergic neurons, induces changes to the expression patterns of P-ERK1/2, disrupts axonal elongation and innervation patterns, and disrupts motor learning abilities.
ContributorsBjorklund, George Reed (Author) / Newbern, Jason M (Thesis advisor) / Neisewander, Janet (Committee member) / Smith, Brian (Committee member) / Orchinik, Miles (Committee member) / Mangone, Marco (Committee member) / Arizona State University (Publisher)
Created2018
Description
The human hairless gene (HR) encodes a 130 kDa transcription factor that is primarily expressed in the brain and skin. In the promoter and 5'-untranslated regions (5'-UTR) of HR, there are three putative consensus p53 responsive elements (p53RE). p53 is a tumor suppressor protein that regulates cell proliferation, apoptosis, and other cell functions. The p53 protein, a known tumor suppressor, acts as a transcription factor and binds to DNA p53REs to activate or repress transcription of the target gene. In general, the p53 binding sequence is 5'-RRRCWWGYYY-3' where W is A or T, and R and Y are purines or pyrimidines, respectively. However, even if the p53 binding sequence does not match the consensus sequence, p53 protein might still be able to bind to the response element. The intent of this investigation was to identify and characterize the p53REs in the promoter and 5'-UTR of HR. If the three p53REs (p53RE1, p53RE2, and p53RE3) are functional, then p53 can bind there and might regulate HR gene expression. The first aim for this thesis was to clone the putative p53REs into a luciferase reporter and to characterize the transcription of these p53REs in glioblastoma (U87 MG) and human embryonic kidney (HEK293) cell lines. Through the transactivation assay, it was discovered that p53REs 2 and 3 were functional in HEK293, but none of the response elements were functional in U87 MG. Since p53 displayed a different regulatory capacity of HR expression in HEK293 and U87 MG cells, the second aim was to verify whether the p53REs are mutated in GBM U87 MG cells by genomic DNA sequencing.
ContributorsMaatough, Anas (Author) / Neisewander, Janet (Thesis director) / Hsieh, Jui-Cheng (Committee member) / Goldstein, Elliott (Committee member) / School of Life Sciences (Contributor) / School of Historical, Philosophical and Religious Studies (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Free coenzyme A (CoASH) carries acyl groups for the tricarboxylic acid (TCA) cycle and fatty acid metabolism, and donates acyl groups for protein posttranslational modifications. Cellular de novo CoASH synthesis starts with a pantothenate kinase (PANK1-3) phosphorylating pantothenate (vitamin B5). Mutations in PANK2 cause a subtype of neurodegeneration with brain iron accumulation (NBIA). The PANKs have differential subcellular distribution and regulatory properties. However, the purpose of each PANK has remained obscure, with knockout mouse models presenting with mild phenotypes unless challenged with a high-fat diet. Based on PANK2’s known activation by palmitoylcarnitine, the PANK2-deficient cells were challenged with palmitic acid (PAL) added to glucose-containing media. The high nutrient mixture generated a surprising “starvation” profile of reduced proliferation, low ATP, AMPK activation, and autophagy upregulation in PANK2-deficient PAL-challenged cells. Further experiments showed that fatty acids accumulated and that PANK2-deficient cells had reduced respiration when provided with palmitoylcarnitine as a substrate, seemingly due to an impaired ability to oxidize fatty acids during PAL-induced Randle Cycle activation. Intriguingly, whole-cell CoASH levels remained stable despite the PAL-induced starvation phenotype, and increasing CoASH via PANK1β overexpression did not rescue the phenotype, demonstrating a unique role for PANK2 in fatty acid metabolism. Even though a direct CoASH deficiency was not detected, there were changes in short chain CoA-derivatives, including acetyl-CoA, succinyl-CoA, and butyryl-CoA, as well as evidence of impaired TCA cycle function. These impairments in both the TCA cycle and fatty acid oxidation implicate a role for PANK2 in regulating mitochondria CoA dynamics.
ContributorsNordlie, Sandra Maria (Author) / Kruer, Michael C (Thesis advisor) / Neisewander, Janet (Thesis advisor) / Padilla Lopez, Sergio (Committee member) / Katsanos, Christos (Committee member) / Arizona State University (Publisher)
Created2022