STX2 Promotes Trophoblast Growth, Migration, and Invasion Through Activation of the PI3K-AKT Pathway in Preeclampsia

Yan Li,Xian-Li Sun,Ying Zhan,Yi-Hao Wang,Chun-Ling Ma,Wen-Ting Li,Chao Li,Can Li

doi:10.3389/fcell.2021.615973

Abstract

ObjectivesAbnormal trophoblast behaviors during pregnancy contribute to the development of preeclampsia (PE). Syntaxin2 (STX2) has been shown to be a crucial epithelial mediator in numerous diseases. However, the functions of STX2 and the mechanisms underlying its role in PE remain largely unknown. The aim of this study was to explore the role of STX2 on trophoblast biology and unravel the molecular mechanisms that contribute to the development and progression of PE.Materials and MethodsWe first compared the expression of STX2 in placental tissues from women with PE and women with normal pregnancies. Then, we investigated the role of STX2 on trophoblast proliferation, migration and invasion in HTR-8/SVneo and primary human trophoblast cells by loss or gain of function experiments. In addition, co-immunoprecipitation, pulldown and immunofluorescence assays were performed to investigate the co-localization of STX2 with other proteins, and to help clarify the mechanisms underlying STX2-mediated functions on trophoblasts.ResultsWe demonstrated that STX2 expression was downregulated in placental tissues of women with PE compared with those from normal pregnancies. Loss and gain of function experiments further confirmed a role for STX2 in cell proliferation, migration and invasion in trophoblasts. By co-immunoprecipitation, pulldown and immunofluorescence co-localization assays, we revealed that STX2 selectively interacted with p85, a subunit of PI3K, and directly recruited p85 to the cytomembrane, thereby activating the AKT signaling pathway. We further demonstrated that the AKT activation was abolished by the use of a PI3K inhibitor (LY294002), which negatively affected STX2-mediated functions on trophoblasts.ConclusionAll together, our findings point to a crucial role for STX2 in PE progression. Our new insights also suggest that STX2 may be a potential diagnostic tool and a novel therapeutic target for treating PE.

Highlights

MATERIALS AND METHODSPreeclampsia (PE) is a pregnancy complication characterized by high blood pressure, excess protein excretion in the urine and multiple organ dysfunction
Using a combination of loss and gain of function experiments, we suggest a role for STX2 in promoting trophoblast growth and invasion potentially via the membrane recruitment of p85, a regulatory subunit of PI3K, which could lead to AKT activation in women with PE
Analysis of STX2 mRNA levels, by qRT-PCR, and of STX2 protein levels, by western blot, in placental tissues further confirmed the IHC results (Figures 1B,C). These results demonstrate that STX2 expression downregulated significantly in the placenta of women with PE

Summary

Introduction

MATERIALS AND METHODSPreeclampsia (PE) is a pregnancy complication characterized by high blood pressure, excess protein excretion in the urine and multiple organ dysfunction. STX2 is involved in the progression and metastasis of various cancers, such as mammary adenocarcinoma (Bascom et al, 2005), hepatocellular carcinoma (Jia et al, 2011), ovarian cancer (Yew et al, 2013), and colorectal cancer (Wang et al, 2018). Overall, these findings suggest a role for STX2 in cell proliferation, invasion and metastasis. The specific biological functions of STX2 and associated molecular mechanisms underlying the development of PE remain largely unknown

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Conclusion