University Distinguished Professors

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Becoming a University Distinguished Professor (UDP) is the highest honor that can be awarded to a faculty member at North Dakota State University. Research from these individuals can be found here. More information about University Distinguished Professors can be found at https://www.ndsu.edu/president/honors/distinguished_professors/

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Browsing University Distinguished Professors by browse.metadata.program "Cellular and Molecular Biology"

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Now showing 1 - 5 of 5
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    Augmented Expression of Apelin/APJ in the Paraventricular Nuclei of Rats after Myocardial Infarction
    (North Dakota State University, 2012) Pingili, Ajeeth Kumar
    Heart failure (HF) is a disease condition in which insufficient blood is pumped through the body. The pathophysiology of HF is multisystematic and includes a collection of different responses to compensate for the inability of the heart to pump the blood with the most important outcome being increased sympathetic nervous system (SNS) activity. Increased SNS activity leads to reclaim the reserved cardiac function. However, this adaptive response is short term and deleterious. The central mechanisms that lead to increased SNS activity during conditions of HF remain enigmatic. APJ, a G-protein-coupled receptor and its endogenous ligand, is a novel neuroendocrine system. Previous studies from us and others indicated that central administration or over expression of apelin in brain cardiovascular regulatory areas resulted in an increase in blood pressure, sympathetic nerve activity and cardiac hypertrophy. The main objective of this study is to determine whether the Apelin/APJ system is involved in increased SNS activation during HF. We created HF rat models by left coronary artery ligation. Apelin and APJ receptor mRNA levels were measured in cardiovascular regions of the brain of sham and myocardial infarction (MI) rats. Results showed a significant increase in the levels of Apelin/APJ mRNA levels in paraventricular nuclei (PVN) and rostral ventrolateral medulla (RVLM) in MI rats as compared to sham rats. To determine the functional role of elevated APJ receptor in these cardiovascular regulatory regions of the brain during HF, we constructed a lentiviral vector carrying an APJ shRNA (Lenti-APJ-shRNA) to knockdown the APJ receptor. Efficiency of the lentiviral vector to knockdown the APJ receptor was confirmed in vitro by transducing a Cath.a cell line and a primary neuronal cell culture with Lenti-APJ-shRNA. In order to determine the effect of silencing of the APJ receptor in vivo, Lenti-APJ-shRNA virus was injected into the PVN of the MI and sham rats. Results showed knockdown of APJ receptor improved left ventricular function and decreased myocardial fibrosis and hypertrophy in MI rats. Thus, this study shows that PVN plays an important role in sympatho excitation and pathophysiology of HF and these findings may help in developing effective therapies for HF.
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    The Discovery of a Novel Growth Hormone Receptor and the Nutritional Regulation of the Growth Related Actions of Growth Hormone
    (North Dakota State University, 2017) Walock, Chad Napoleon
    The growth hormone (GH) family peptides such as GH, prolactin (PRL), and somatolactin (SL) regulate a wide array of physiological actions including but not limited to growth, metabolism, osmoregulation, and lipolysis. These actions are regulated by many factors both internal and external. I used rainbow trout (Oncorhynchus mykiss) as a model organism to study the effects of GH-family peptides, nutritional state, and serum on insulin-like growth factor (IGF) and growth hormone receptor (GHR) expression. Gene sequencing and phylogenic analysis was applied to characterize a novel GHR. Real-time quantitative-PCR was used to determine IGF and GHR expression levels in liver, muscle, and adipose tissue. Western blotting and pharmacological inhibitors were used to determine signaling pathways. A novel GHR was characterized and determined to be a type 1 GHR with a diverse distribution. It was found to have many features conserved in other GHRs including binding regions, a Y/FGEFS motif, cysteine residues, and N-glycosylation sites. Fasting was shown to decrease GHR1 expression in the liver, adipose tissue and red muscle. GH and PRL were shown to stimulate IGF expression through the ERK, PI3K/Akt, and JAK-STAT signaling pathways. GH-stimulated IGF expression was dependent on nutritional state, as GH was only able to stimulate IGF expression in fed fish. Nutritional state has no direct effect on GH-stimulated GHR expression. Serum was determined to be the mediator of the change in GH sensitivity as pre-treatment with serum from cells of an opposite nutritional state caused cells to react like the opposite nutritional state in GH-stimulated IGF expression. These findings contribute to the understanding of the actions of GH-family peptides and the mechanisms through which GH conducts its diverse actions in times of differing nutritional availability.
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    Effects of Environmental Estrogens on the Growth Hormone-Insulin-Like Growth Factor System in Rainbow Trout (Oncorhynchus Mykiss)
    (North Dakota State University, 2013) Hanson, Andrea M.
    The increasing production, use, and disposal of an expanding array of chemicals that enter the environment pose a serious threat to terrestrial and aquatic animals, as well as to humans. Fish in aquatic habitats are exposed to increasing concentrations of environmental contaminants, including environmental estrogens (EE). In this work, rainbow trout were used to assess the effects of EE on the growth hormone (GH)-insulin-like growth factor (IGF) system, specifically focusing on osmoregulation, organismal growth, and growth at the molecular level. Juvenile trout were exposed to varying concentrations of 17â-estradiol (E2), â-sitosterol (âS), and 4-n-nonylphenol (NP) in vivo and in vitro. Real-time quantitative-PCR was used to measure levels of mRNA expression (GH receptor 1 (GHR1), GHR2, IGF-1, IGF-2, IGF receptor 1A (IGFR1A), and IGFR1B) in multiple tissues, including liver, gill, and muscle. Western blotting was used to elucidate signaling pathways affected by EE-treatment (e.g., JAK-STAT, MAPK, PI3K). Environmental estrogen-treated fish displayed depressed growth in terms of body mass and body length. The observed effects on organismal growth appeared to be due to a decrease in food conversion, as food consumption was not significantly different between treatment groups. Hepatic, gill, and muscle levels of mRNAs encoding GHR1, GHR2, IGF-1, IGF-2, IGFR1A, and IGFR1B decreased in a concentration-, time-, and compound-dependent manner in vivo and in vitro. Furthermore, EE-treated fish displayed decreased osmoregulatory function when subjected to a salt water challenge, as evaluated by measuring plasma chloride levels and mRNA expression of GHRs, IGFs, and IGFRs. The suppression of mRNA expression of components of the GH-IGF system by EE was linked to suppressed phosphorylation of JAK-STAT, MAPK, and PI3K-Akt in a concentration- and time-dependent manner in hepatocytes and gill filaments, an effect that was ER-dependent. Classically, the ER has been thought to function as a nuclear receptor; however, the observed results support the notion that the ER (and thus EE) may have nongenomic effects as well. The results of this dissertation indicate that EE suppress growth at the organismal and molecular level via inhibition of growth-related signaling cascades and repression of gene expression elements of the GH-IGF system.
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    The Role of Platelet-Derived Growth Factor Receptor Signaling in Medulloblastoma Metastasis
    (North Dakota State University, 2013) Bhat, Kruttika Narayan
    Medulloblastoma is the most common brain tumor in children and one third of the patients remain incurable. Tumor metastasis is one of the primary reasons for its high mortality rate. Despite evidence of overexpression of PDGFRα and PDGFRβ in metastatic medulloblastoma, their individual roles remain controversial and equivocal. Analysis of their specific signaling pathway in medulloblastoma cells revealed that PDGFRα and PDGFRβ signaling events lead to distinct cellular functions: while PDGFRβ stimulated cell proliferation and invasion, the expression of CD44 to regulate progression via c-Myc and inhibited cell death, PDGFRα displayed the opposite effects. Studies also revealed that c-Myc plays an intermediary role by regulating the downstream molecules in PDGFRβ signal pathway such as CD44 and NFB. NFB activity was found to be down- regulated in the absence of PDGFRβ pathway, with its activity restored by the overexpression of c-Myc. Analysis of medulloblastoma patient tissues without a prior knowledge of their metastatic nature further confirmed that PDGFRβ-CD44 axis regulate medulloblastoma metastasis. Co-inhibition studies performed by simultaneous inhibition of both PDGFRβ and c-Myc either by using siRNAs or by using pharmacological inhibitors demonstrated an enhanced inhibitory effect on medulloblastoma cell proliferation and migration. Using miRNA profiling of Daoy cells lacking either PDGFRβ or c-Myc alone or both, a set of miRNAs regulated by both PDGFRβ and c-Myc in common were identified. Integrative analysis of these miRNAs and their targets revealed that activation of PDGFRβ signaling and overexpression of c-Myc may enhance medulloblastoma progression via modulating the expression of several miRNAs such as miR-1280, -1260 and consequently regulating the expression of oncogenic molecules, such as Jagged 2 and CDC25A, respectively. Specific inhibition of miRNAs, miR-1280 and -1260, and JAG2 demonstrated their vital roles in medulloblastoma cell proliferation and migration. These findings suggest that the PDGFRβ-CD44 is a regulatory axis modulating medulloblastoma progression via c-Myc and targeting PDGFRβ/c-Myc/CD44 may provide a novel therapeutic strategy for the treatment of metastatic medulloblastoma.
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    Structural Studies of BECN1, A Key Autophagy Protein, and Intrinsically Disordered Regions in Autophagy Proteins
    (North Dakota State University, 2016) Mei, Yang
    Autophagy, a conserved catabolic process required for cellular homeostasis in eukaryotes, is regulated by many proteins. The central goal of my doctoral research is to investigate conformational flexibility of autophagy proteins, with a special focus on BECN1, a core component of the class III phosphatidylinositol-3 kinase autophagosome nucleation complex that may serve as an autophagy interaction hub. Our rigorous bioinformatics analysis predicts that 57% of 59 key human autophagy proteins contain intrinsically disordered regions (IDRs), which lack stable secondary and tertiary structure. The prevalence of IDRs suggests that IDRs play an important, yet hitherto uninvestigated, role in autophagy. We confirm disorder of selected IDRs via biophysical methods, and use additional bioinformatics tools to predict protein-protein interaction and phosphorylation sites within IDRs, identifying potential biological functions. We experimentally investigate four distinct BECN1 domains: (i) The IDR, which includes a functional BCL2 homology 3 domain (BH3D) that binds BCL2 proteins, undergoing a binding-associated disorder-to-helix transition and enabling BCL2s to inhibit autophagy. (ii) The flexible helical domain (FHD) which has an unstructured N-terminal half and structured Cterminal half forming a 2.5-turn helix in our 2.0 Å X-ray crystal structure. Our molecular dynamics simulations and circular dichroism spectroscopy analyses indicate the FHD transiently samples more helical conformations and likely undergoes a binding-associated disorder-to-helix transition. We also show that the FHD bears conserved residues critical for AMBRA1 interaction and for starvation-induced autophagy. (iii) A coiled-coil domain (CCD) which forms an antiparallel homodimer in our 1.46 Å X-ray crystal structure. We have also built a atomistic model of an optimally packed, parallel BECN1:ATG14 CCD heterodimer that agrees with our experimental SAXS data. Further, we show that BECN1:ATG14 heterodimer interface residues identified from this model are important for heterodimer formation and starvation-induced autophagy. (iv) A β-α repeated autophagy-specific domain which bears invariant residues that we show are important for starvation-induced autophagy. Thus, we demonstrate that conformational flexibility is a key BECN1 feature. Lastly, we show that multi-domain BECN1 constructs have extended conformations with no intra-domain interactions that impact structure of other domains, suggesting that BECN1 structure and conformational flexibility enable its function as an autophagy interaction hub.