Inhibition of decidual IGF-1 signaling in response to hypoxia and leucine deprivation is mediated by mTOR and AAR pathways and increased IGFBP-1 phosphorylation

Majida Abu Shehab; Kyle Biggar; Jenica H Kakadia; Manthan Dhruv; Bhawani Jain; Pinki Nandi; Karen Nygard; Thomas Jansson; Madhulika B Gupta

doi:10.1016/j.mce.2020.110865

Inhibition of decidual IGF-1 signaling in response to hypoxia and leucine deprivation is mediated by mTOR and AAR pathways and increased IGFBP-1 phosphorylation

Mol Cell Endocrinol. 2020 Jul 15:512:110865. doi: 10.1016/j.mce.2020.110865. Epub 2020 Jun 5.

Authors

Majida Abu Shehab¹, Kyle Biggar², Jenica H Kakadia³, Manthan Dhruv³, Bhawani Jain³, Pinki Nandi¹, Karen Nygard⁴, Thomas Jansson⁵, Madhulika B Gupta⁶

Affiliations

¹ Department of Pediatrics, University of Western Ontario, London, ON, Canada.
² Department of Biology and Institute of Biochemistry, Carleton University, Ottawa, ON, Canada. Electronic address: kyle_biggar@carleton.ca.
³ Department of Biochemistry, University of Western Ontario, London, ON, Canada.
⁴ Biotron Integrated Microscopy Facility, University of Western Ontario, London, ON, Canada.
⁵ Department of Obstetrics and Gynecology, Division of Reproductive Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
⁶ Department of Pediatrics, University of Western Ontario, London, ON, Canada; Department of Biochemistry, University of Western Ontario, London, ON, Canada; Children's Health Research Institute, London, ON, Canada. Electronic address: mbgupta@uwo.ca.

PMID: 32502935
DOI: 10.1016/j.mce.2020.110865

Abstract

Decidual mechanistic target of rapamycin (mTOR) is inhibited, amino acid response (AAR) and protein kinase CK2 are activated, and IGF (insulin-like growth factor) binding protein (IGFBP)-1 is hyperphosphorylated in human intrauterine growth restriction (IUGR). Using decidualized human immortalized endometrial stromal cells (HIESC), we hypothesized that hypoxia and leucine deprivation causing inhibition of decidual IGF-1 signaling is mediated by mTOR, AAR, CK2 and IGFBP-1 phosphorylation. Mass spectrometry demonstrated that hypoxia (1% O₂) or rapamycin increased IGFBP-1 phosphorylation singly at Ser101/119/169 (confirmed using immunoblotting) and dually at pSer169 + 174. Hypoxia resulted in mTOR inhibition, AAR and CK2 activation, and decreased IGF-1 bioactivity, with no additional changes with rapamycin + hypoxia. Rapamycin and/or hypoxia promoted colocalization of IGFBP-1 and CK2 (dual-immunofluorescence and proximity ligation assay). Leucine deprivation showed similar outcomes. Changes in IGFBP-1 phosphorylation regulated by mTOR/AAR signaling and CK2 may represent a novel mechanism linking oxygen and nutrient availability to IGF-1 signaling in the decidua.

Keywords: Biological availability; Humans; Intrauterine growth restriction; Maternal-fetal exchange; Pregnancy.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Amino Acid Transport Systems / metabolism
Casein Kinase II / metabolism
Cell Hypoxia / physiology*
Cells, Cultured
Decidua / drug effects
Decidua / metabolism*
Down-Regulation / drug effects
Female
Humans
Insulin-Like Growth Factor Binding Protein 1 / metabolism
Leucine / deficiency*
Leucine / pharmacology
Phosphorylation
Receptors, Amino Acid / metabolism
Signal Transduction / drug effects
Signal Transduction / physiology
Sirolimus / pharmacology
TOR Serine-Threonine Kinases / metabolism

Substances

Amino Acid Transport Systems
IGFBP1 protein, human
Insulin-Like Growth Factor Binding Protein 1
Receptors, Amino Acid
MTOR protein, human
Casein Kinase II
TOR Serine-Threonine Kinases
Leucine
Sirolimus

Grants and funding

R01 HD089980/HD/NICHD NIH HHS/United States