Small GTP-binding protein Rap1 mediates EGF and HB-EGF signaling and modulates EGF receptor expression in HTR-8/SVneo extravillous trophoblast cells

Mikihiro Yoshie; Kensuke Ohishi; Gen Ishikawa; Atsuya Tsuru; Kazuya Kusama; Mana Azumi; Kazuhiro Tamura

doi:10.1002/rmb2.12537

Small GTP-binding protein Rap1 mediates EGF and HB-EGF signaling and modulates EGF receptor expression in HTR-8/SVneo extravillous trophoblast cells

Reprod Med Biol. 2023 Aug 21;22(1):e12537. doi: 10.1002/rmb2.12537. eCollection 2023 Jan-Dec.

Authors

Mikihiro Yoshie¹, Kensuke Ohishi¹, Gen Ishikawa², Atsuya Tsuru¹, Kazuya Kusama¹, Mana Azumi¹, Kazuhiro Tamura¹

Affiliations

¹ Department of Endocrine Pharmacology Tokyo University of Pharmacy and Life Sciences Tokyo Japan.
² Department of Obstetrics Miyagi Children's Hospital Sendai Japan.

Abstract

Purpose: Extravillous trophoblasts (EVTs) invade the endometrium to establish a fetomaternal interaction during pregnancy. Epidermal growth factor (EGF) and heparin-binding EGF-like growth factor (HB-EGF) stimulate EVT invasion by binding to the EGF receptor (EGFR). We examined the role of the small GTP-binding protein Rap1 in EGF- and HB-EGF-stimulated EVT invasion.

Methods: Expression of Rap1 in the first-trimester placenta was examined by immunohistochemistry. Effect of EGF or HB-EGF on Rap1 activation (GTP-Rap1) and Rap1 knockdown on invasion was assessed in EVT cell line (HTR-8/SVneo). In addition, effect of Rap1 knockdown and Rap1GAP (a Rap1 inactivator) overexpression on the activation of EGF signaling and EGFR expression were examined.

Results: Rap1 was expressed by EVTs, villous cytotrophoblasts, and syncytiotrophoblasts in the placenta. EGF and HB-EGF activated Rap1 and promoted invasion of HTR-8/SVneo, and these effects were inhibited by Rap1 knockdown. The EGF- and HB-EGF-induced phosphorylation of AKT, ERK1/2, p38MAPK, and Src was inhibited by Rap1 knockdown. Furthermore, the knockdown of Rap1 reduced the EGFR protein level. Overexpression of Rap1GAP repressed EGF- and HB-EGF-induced Rap1 activation and reduced EGFR expression.

Conclusion: Rap1 may function as a mediator of EGF and HB-EGF signaling pathways and can modulate EGFR expression in EVTs during placental development.

Keywords: EGF; HB‐EGF; Rap1; extravillous trophoblast; invasion.