Electronic Thesis and Dissertation Repository


Master of Science




Dr. Madhulika Gupta


In this study, we provide novel evidence for a role of fetal liver mTOR signaling in regulating IGF-I bioavailability by modulating IGFBP-1 phosphorylation due to hypoxia – a key factor in the development of reduced fetal growth in utero. We utilized HepG2 cells in vitro and demonstrated a link between mTOR inhibition and hypoxia-induced IGFBP-1 phosphorylation. Using a biological assay for IGF-I receptor autophosphorylation, we demonstrated a functional significance for hypoxia-induced IGFBP-1 phosphorylation in reducing IGF-I bioactivity in vitro. Further, we have implicated a mechanistic link to increased CK2 activity within this regulation. We demonstrate that mTOR inhibition induced IGFBP-1 phosphorylation, which was not further enhanced by hypoxia, and that mTOR activation prevented hypoxia-induced IGFBP-1 phosphorylation. Together, we have identified a new mechanism involving mTOR inhibition during hypoxia by which IGFBP-1 phosphorylation, and thus IGF-I bioavailability, is regulated, and also implicate increased CK2 activity as an intermediate process in this mechanism.

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