Mechanistic Target of Rapamycin Complex 1 Signaling Links Hypoxia to Increased IGFBP-1 Phosphorylation in Primary Human Decidualized Endometrial Stromal Cells

Biomolecules. 2021 Sep 18;11(9):1382. doi: 10.3390/biom11091382.

Abstract

Insulin-like growth factor-1 (IGF-1) bioavailability in pregnancy is governed by IGF binding protein (IGFBP-1) and its phosphorylation, which enhances the affinity of IGFBP-1 for the growth factor. The decidua is the predominant source of maternal IGFBP-1; however, the mechanisms regulating decidual IGFBP-1 secretion/phosphorylation are poorly understood. Using decidualized primary human endometrial stromal cells (HESCs) from first-trimester placenta, we tested the hypothesis that mTORC1 signaling mechanistically links hypoxia to decidual IGFBP-1 secretion/phosphorylation. Hypoxia inhibited mechanistic target of rapamycin (mTORC1) (p-P70-S6K/Thr389, -47%, p = 0.038; p-4E-BP1/Thr70, -55%, p = 0.012) and increased IGFBP-1 (total, +35%, p = 0.005; phosphorylated, Ser101/+82%, p = 0.018; Ser119/+88%, p = 0.039; Ser 169/+157%, p = 0.019). Targeted parallel reaction monitoring-mass spectrometry (PRM-MS) additionally demonstrated markedly increased dual IGFBP-1 phosphorylation (pSer98+Ser101; pSer169+Ser174) in hypoxia. IGFBP-1 hyperphosphorylation inhibited IGF-1 receptor autophosphorylation/ Tyr1135 (-29%, p = 0.002). Furthermore, silencing of tuberous sclerosis complex 2 (TSC2) activated mTORC1 (p-P70-S6K/Thr389, +68%, p = 0.038; p-4E-BP1/Thr70, +30%, p = 0.002) and reduced total/site-specific IGFBP-1 phosphorylation. Importantly, TSC2 siRNA prevented inhibition of mTORC1 and the increase in secretion/site-specific IGFBP-1 phosphorylation in hypoxia. PRM-MS indicated concomitant changes in protein kinase autophosphorylation (CK2/Tyr182; PKC/Thr497; PKC/Ser657). Overall, mTORC1 signaling mechanistically links hypoxia to IGFBP-1 secretion/phosphorylation in primary HESC, implicating decidual mTORC1 inhibition as a novel mechanism linking uteroplacental hypoxia to fetal growth restriction.

Keywords: IGF Type 1; fetal development; humans; insulin-like growth factor I; placental insufficiency; receptor.

Publication types

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

MeSH terms

  • Adult
  • Casein Kinase II / metabolism
  • Cell Hypoxia
  • Cell Shape
  • Cells, Cultured
  • Decidua / pathology*
  • Female
  • Gene Silencing
  • Humans
  • Insulin-Like Growth Factor Binding Protein 1 / metabolism*
  • Insulin-Like Growth Factor I / metabolism
  • Mechanistic Target of Rapamycin Complex 1 / metabolism*
  • Phosphorylation
  • Pregnancy
  • Pregnancy Trimester, First / physiology
  • Protein Kinase C / metabolism
  • RNA, Small Interfering / metabolism
  • Receptor, IGF Type 1 / metabolism
  • Signal Transduction*
  • Stromal Cells / metabolism
  • Stromal Cells / pathology
  • Tuberous Sclerosis Complex 2 Protein / metabolism
  • Young Adult

Substances

  • IGF1R protein, human
  • Insulin-Like Growth Factor Binding Protein 1
  • RNA, Small Interfering
  • TSC2 protein, human
  • Tuberous Sclerosis Complex 2 Protein
  • Insulin-Like Growth Factor I
  • Receptor, IGF Type 1
  • Casein Kinase II
  • Mechanistic Target of Rapamycin Complex 1
  • Protein Kinase C