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Kakadia JH, Khalid MU, Heinemann IU, Han VK. AMPK-mTORC1 pathway mediates hepatic IGFBP-1 phosphorylation in glucose deprivation: a potential molecular mechanism of hypoglycemia-induced impaired fetal growth. J Mol Endocrinol 2024; 72:e230137. [PMID: 38194365 PMCID: PMC10895286 DOI: 10.1530/jme-23-0137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 01/09/2024] [Indexed: 01/10/2024]
Abstract
Mechanisms underlying limitations in glucose supply that restrict fetal growth are not well established. IGF-1 is an important regulator of fetal growth and IGF-1 bioavailability is markedly inhibited by IGFBP-1 especially when the binding protein is hyperphosphorylated. We hypothesized that the AMPK-mTORC1 pathway increases IGFBP-1 phosphorylation in response to glucose deprivation. Glucose deprivation in HepG2 cells activated AMPK and TSC2, inhibited mTORC1 and increased IGFBP-1 secretion and site-specific phosphorylation. Glucose deprivation also decreased IGF-1 bioavailability and IGF-dependent activation of IGF-1R. AICAR (an AMPK activator) activated TSC2, inhibited mTORC1, and increased IGFBP-1 secretion/phosphorylation. Further, siRNA silencing of either AMPK or TSC2 prevented mTORC1 inhibition and IGFBP-1 secretion and phosphorylation in glucose deprivation. Our data suggest that the increase in IGFBP-1 phosphorylation in response to glucose deprivation is mediated by the activation of AMPK/TSC2 and inhibition of mTORC1, providing a possible mechanistic link between glucose deprivation and restricted fetal growth.
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Affiliation(s)
- Jenica H Kakadia
- Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
- Children's Health Research Institute, London, Ontario, Canada
| | - Muhammad U Khalid
- Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Ilka U Heinemann
- Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Victor K Han
- Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
- Children's Health Research Institute, London, Ontario, Canada
- Department of Pediatrics, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
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Rosario FJ, Chopra A, Biggar K, Powell TL, Gupta MB, Jansson T. Placental Remote Control of Fetal Metabolism: Trophoblast mTOR Signaling Regulates Liver IGFBP-1 Phosphorylation and IGF-1 Bioavailability. Int J Mol Sci 2023; 24:7273. [PMID: 37108437 PMCID: PMC10138459 DOI: 10.3390/ijms24087273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 04/02/2023] [Accepted: 04/06/2023] [Indexed: 04/29/2023] Open
Abstract
The mechanisms mediating the restricted growth in intrauterine growth restriction (IUGR) remain to be fully established. Mechanistic target of rapamycin (mTOR) signaling functions as a placental nutrient sensor, indirectly influencing fetal growth by regulating placental function. Increased secretion and the phosphorylation of fetal liver IGFBP-1 are known to markedly decrease the bioavailability of IGF-1, a major fetal growth factor. We hypothesized that an inhibition of trophoblast mTOR increases liver IGFBP-1 secretion and phosphorylation. We collected conditioned media (CM) from cultured primary human trophoblast (PHT) cells with a silenced RAPTOR (specific inhibition of mTOR Complex 1), RICTOR (inhibition of mTOR Complex 2), or DEPTOR (activates both mTOR Complexes). Subsequently, HepG2 cells, a well-established model for human fetal hepatocytes, were cultured in CM from PHT cells, and IGFBP-1 secretion and phosphorylation were determined. CM from PHT cells with either mTORC1 or mTORC2 inhibition caused the marked hyperphosphorylation of IGFBP-1 in HepG2 cells as determined by 2D-immunoblotting while Parallel Reaction Monitoring-Mass Spectrometry (PRM-MS) identified increased dually phosphorylated Ser169 + Ser174. Furthermore, using the same samples, PRM-MS identified multiple CK2 peptides coimmunoprecipitated with IGFBP-1 and greater CK2 autophosphorylation, indicating the activation of CK2, a key enzyme mediating IGFBP-1 phosphorylation. Increased IGFBP-1 phosphorylation inhibited IGF-1 function, as determined by the reduced IGF-1R autophosphorylation. Conversely, CM from PHT cells with mTOR activation decreased IGFBP-1 phosphorylation. CM from non-trophoblast cells with mTORC1 or mTORC2 inhibition had no effect on HepG2 IGFBP-1 phosphorylation. Placental mTOR signaling may regulate fetal growth by the remote control of fetal liver IGFBP-1 phosphorylation.
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Affiliation(s)
- Fredrick J. Rosario
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Anand Chopra
- Institute of Biochemistry, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Kyle Biggar
- Institute of Biochemistry, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Theresa L. Powell
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Section of Neonatology, Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Department of Biochemistry, University of Western Ontario, London, ON N6A 3K7, Canada
| | - Madhulika B. Gupta
- Department of Biochemistry, University of Western Ontario, London, ON N6A 3K7, Canada
- Department of Pediatrics, University of Western Ontario, London, ON N6A 3K7, Canada
- Children’s Health Research Institute, University of Western Ontario, London, ON N6A 3K7, Canada
| | - Thomas Jansson
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
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Gupta MB, Biggar KK, Li C, Nathanielsz PW, Jansson T. Increased Colocalization and Interaction Between Decidual Protein Kinase A and Insulin-like Growth Factor-Binding Protein-1 in Intrauterine Growth Restriction. J Histochem Cytochem 2022; 70:515-530. [PMID: 35801847 DOI: 10.1369/00221554221112702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Increased phosphorylation of decidual insulin-like growth factor-binding protein-1 (IGFBP-1) can contribute to intrauterine growth restriction (IUGR) by decreasing the bioavailability of insulin-like growth factor-1 (IGF-1). However, the molecular mechanisms regulating IGFBP-1 phosphorylation at the maternal-fetal interface are poorly understood. Protein kinase A (PKA) is required for normal decidualization. Consensus sequences for PKA are present in IGFBP-1. We hypothesized that the expression/interaction of PKA with decidual IGFBP-1 is increased in IUGR. Parallel reaction monitoring-mass spectrometry (PRM-MS) identified multiple PKA peptides (n=>30) co-immunoprecipitating with IGFBP-1 in decidualized primary human endometrial stromal cells (HESC). PRM-MS also detected active PKApThr197 and greater site-specific IGFBP-1 phosphorylation(pSer119), (pSer98+pSer101) (pSer169+pSer174) in response to hypoxia. Hypoxia promoted colocalization [dual immunofluorescence (IF)] of PKA with IGFBP-1 in decidualized HESC. Colocalization (IF) and interaction (proximity ligation assay) of PKA and IGFBP-1 were increased in decidua collected from placenta of human IUGR pregnancies (n=8) compared with decidua from pregnancies with normal fetal growth. Similar changes were detected in decidual PKA/IGFBP-1 using placenta from baboons subjected to maternal nutrient reduction (MNR) vs controls (n=3 each). In baboons, these effects were evident in MNR at gestational day 120 prior to IUGR onset. Increased PKA-mediated phosphorylation of decidual IGFBP-1 may contribute to decreased IGF-1 bioavailability in the maternal-fetal interface in IUGR.
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Affiliation(s)
- Madhulika B Gupta
- Department of Biochemistry and Department of Pediatrics, University of Western Ontario, London, ON, Canada.,Children's Health Research Institute, London, ON, Canada
| | - Kyle K Biggar
- Institute of Biochemistry, Carleton University, Ottawa, ON, Canada
| | - Cun Li
- University of Wyoming, Laramie, Wyoming
| | | | - Thomas Jansson
- Southwest National Primate Research Center, San Antonio, Texas.,Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, Colorado
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