Aspartyl-Asparaginyl-β-Hydroxylase (AAH) Regulation and Function in Liver Disease

Lizarazo, Diana

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Year:: 2014
Contributor:: Lizarazo, Diana (creator); de la Monte, Suzanne (Director); Wands, Jack (Reader); Salomon, Arthur (Reader); Harnett, Karen (Reader); Britt, Deborah (Reader); Brown University. BIOMED: Molecular Pharmacology, Physiology, and Biotechnology (sponsor)
Genre:: theses
Subject:: hepatocellular carcinoma; insulin-like growth factor; aspartyl-asparaginyl-β-hydroxylase; Notch; Liver--Cancer; Alcoholic liver diseases; Ceramides; Cell migration; Insulin; Somatomedin; Phosphorylation
Extent:: xxviii, 230 p.
DOI: https://doi.org/10.7301/Z0VH5M5K

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Abstract:: Aspartyl-asparaginyl-β-hydroxylase (AAH) is a ~86 kD protein abundantly expressed in hepatocellular carcinoma (HCC) and downregulated by chronic ethanol exposure, contributing to alcoholic liver disease (ALD). AAH expression is stimulated by insulin and insulin-like growth factor-1 (IGF-1) signaling networks. Insulin/IGF-1 signaling is over-activated in HCCs, but inhibited by ethanol exposure, partly due to aberrant ceramide accumulation. AAH promotes cell adhesion, migration, and invasion partly through the hydroxylation of Notch-1 and Jagged-1 and attendant activation of Notch signaling. Insulin/IGF-1 signaling networks regulate AAH at the transcriptional, as well as the post-translational levels. More specifically, AAH may be post-translationally regulated by phosphorylation since inhibition of glycogen synthase kinase-3β (GSK-3β) increases AAH protein and migration, while GSK-3β overexpression yields the opposite effects. Correspondingly, sub-sequence analysis of AAH protein demonstrated a number of potential phosphorylation sites corresponding to GSK-3β, as well as protein kinase A (PKA), protein kinase C (PKC), and casein kinase 2 (CK2). To investigate the regulation of AAH in the liver, liver tissue or liver slice cultures from Long Evans rats were exposed to ethanol and a ceramide inhibitor or insulin sensitizing treatments to examine the effects on insulin/IGF-1, AAH, and Notch signaling activation. Human hepatoma-derived Huh7 cells served to characterize the effects of IGF-1 stimulation on AAH protein and the post-translational regulation of AAH by phosphorylation, using chemical inhibitors of GSK-3β, PKA, PKC, or CK2, or using AAH mutants lacking individual phosphorylation sites. The findings demonstrated that inhibition of ceramide synthesis restored ethanol-impaired insulin/IGF-1 signaling, expression of AAH and Notch signaling proteins in the liver. Furthermore, IGF-1 signaling promoted AAH expression and subcellular trafficking with consequences on the activation of Notch signaling. Lastly, the findings suggest AAH protein is post-translationally regulated by phosphorylation at multiple sites, possibly through priming mechanisms of phosphorylation. The investigations shed light on the regulation of AAH protein expression and function as it relates to the activation of Notch signaling and its dysregulation in HCC and ALD.
Notes:: Thesis (Ph.D. -- Brown University (2014)

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Citation

Lizarazo, Diana, "Aspartyl-Asparaginyl-β-Hydroxylase (AAH) Regulation and Function in Liver Disease" (2014). Molecular Pharmacology, Physiology, and Biotechnology Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0VH5M5K

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Molecular Pharmacology, Physiology, and Biotechnology Theses and Dissertations

Theses and Dissertations for the Molecular Pharmacology, Physiology, and Biotechnology department.
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