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Matsukawa H, Ikezaki M, Nishioka K, Iwahashi N, Fujimoto M, Nishitsuji K, Ihara Y, Ino K. Calnexin Is Involved in Forskolin-induced Syncytialization in Cytotrophoblast Model BeWo Cells. Biomolecules 2022; 12:biom12081050. [PMID: 36008943 PMCID: PMC9405722 DOI: 10.3390/biom12081050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 07/26/2022] [Accepted: 07/26/2022] [Indexed: 11/16/2022] Open
Abstract
Calnexin (CNX), a membrane-bound molecular chaperone, is involved in protein folding and quality control of nascent glycoproteins in the endoplasmic reticulum. We previously suggested critical roles of calreticulin, a functional paralogue of CNX, in placentation, including invasion of extravillous trophoblasts and syncytialization of cytotrophoblasts. However, the roles of CNX in placentation are unclear. In human choriocarcinoma BeWo cells, which serve as an experimental model of syncytialization, CNX knockdown suppressed forskolin-induced cell fusion and β-human chorionic gonadotropin (β-hCG) induction. Cell-surface luteinizing hormone/chorionic gonadotropin receptor, a β-hCG receptor, was significantly down-regulated in CNX-knockdown cells, which suggested the presence of a dysfunctional autocrine loop of β-hCG up-regulation. In this study, we also found abundant CNX expression in normal human placentas. Collectively, our results revealed the critical role of CNX in the syncytialization-related signaling in a villous trophoblast model and suggest a link between CNX expression and placenta development.
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Affiliation(s)
- Hitomi Matsukawa
- Department of Obstetrics and Gynecology, School of Medicine, Wakayama Medical University, Wakayama 641-8509, Japan; (H.M.); (K.N.); (N.I.); (K.I.)
| | - Midori Ikezaki
- Department of Biochemistry, School of Medicine, Wakayama Medical University, Wakayama 641-8509, Japan; (M.I.); (K.N.)
| | - Kaho Nishioka
- Department of Obstetrics and Gynecology, School of Medicine, Wakayama Medical University, Wakayama 641-8509, Japan; (H.M.); (K.N.); (N.I.); (K.I.)
| | - Naoyuki Iwahashi
- Department of Obstetrics and Gynecology, School of Medicine, Wakayama Medical University, Wakayama 641-8509, Japan; (H.M.); (K.N.); (N.I.); (K.I.)
| | - Masakazu Fujimoto
- Department of Diagnostic Pathology, Kyoto University, Kyoto 606-8507, Japan;
| | - Kazuchika Nishitsuji
- Department of Biochemistry, School of Medicine, Wakayama Medical University, Wakayama 641-8509, Japan; (M.I.); (K.N.)
| | - Yoshito Ihara
- Department of Biochemistry, School of Medicine, Wakayama Medical University, Wakayama 641-8509, Japan; (M.I.); (K.N.)
- Correspondence: ; Tel.: +81-73-441-0628
| | - Kazuhiko Ino
- Department of Obstetrics and Gynecology, School of Medicine, Wakayama Medical University, Wakayama 641-8509, Japan; (H.M.); (K.N.); (N.I.); (K.I.)
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Extracellularly Released Calreticulin Induced by Endoplasmic Reticulum Stress Impairs Syncytialization of Cytotrophoblast Model BeWo Cells. Cells 2021; 10:cells10061305. [PMID: 34073978 PMCID: PMC8225044 DOI: 10.3390/cells10061305] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 05/20/2021] [Accepted: 05/21/2021] [Indexed: 12/12/2022] Open
Abstract
The pregnancy-specific syndrome preeclampsia is a major cause of maternal mortality throughout the world. The initial insult resulting in the development of preeclampsia is inadequate trophoblast invasion, which may lead to reduced maternal perfusion of the placenta and placental dysfunction, such as insufficient trophoblast syncytialization. Endoplasmic reticulum (ER) stress has been implicated in the pathology of preeclampsia and serves as the major risk factor. Our previous studies suggested critical roles of calreticulin (CRT), which is an ER-resident stress response protein, in extravillous trophoblast invasion and cytotrophoblast syncytialization. Here, we studied the mechanism by which ER stress exposes the placenta to the risk of preeclampsia. We found that CRT was upregulated in the serum samples, but not in the placental specimens, from preeclamptic women. By using BeWo cells, an established model of cytotrophoblasts that syncytialize in the presence of forskolin, we demonstrated that thapsigargin-induced ER stress caused extracellular release of CRT from BeWo cells and that the extracellular CRT suppressed forskolin-induced release of β-human chorionic gonadotropin and altered subcellular localization of E-cadherin, which is a key adhesion molecule associated with syncytialization. Our results together provide evidence that induction of ER stress leads to extracellular CRT release, which may contribute to placental dysfunction by suppressing cytotrophoblast syncytialization.
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