Syncytin proteins incorporated in placenta exosomes are important for cell uptake and show variation in abundance in serum exosomes from patients with preeclampsia

FASEB J. 2014 Aug;28(8):3703-19. doi: 10.1096/fj.13-239053. Epub 2014 May 8.


Exosomes are extracellular vesicles that mediate intercellular communication and are involved in several biological processes. The objective of our study was to determine whether endogenous retrovirus group WE, member l (ERVWE1)/syncytin-1 and endogenous retrovirus group FRD, member 1 (ERVFRDE1)/syncytin-2, encoded by human endogenous retrovirus (HERV) envelope (env) genes, are present at the surface of exosomes produced by placenta-derived villous cytotrophoblasts and whether they play a role in cellular uptake of exosomes. In addition, we sought to determine whether these proteins are present in various abundances in serum-derived exosomes from normal pregnant women vs. women with preeclampsia (PE). Isolated exosomes were analyzed for their content by Western blot, a bead-associated flow cytometry approach, and a syncytin-2 ELISA. Binding and uptake were tested through confocal and electron microscopy using the BeWo choriocarcinoma cell line. Quality control of exosome preparations consisted of detection of exosomal and nonexosomal markers. Exosome-cell interactions were compared between cells incubated in the presence of control exosomes, syncytin-1 or syncytin-2-deprived exosomes, or exosomes solely bearing the uncleaved forms of these HERV env proteins. From our data, we conclude that villous cytotrophoblast exosomes are positive for both env proteins and are rapidly taken up by BeWo cells in a syncytin-1- and syncytin-2-dependent manner and that syncytin-2 is reduced in serum-derived exosomes from women with PE when compared to exosomes from normal pregnant women.

Keywords: HERV; biomarker; fusogenic protein; microvesicles; villous cytotrophoblasts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amino Acid Transport System ASC / antagonists & inhibitors
  • Amino Acid Transport System ASC / genetics
  • Amino Acid Transport System ASC / physiology
  • Cell Communication
  • Cell Fusion
  • Cell Line, Tumor
  • Choriocarcinoma / pathology
  • Endocytosis
  • Endogenous Retroviruses / genetics
  • Endogenous Retroviruses / physiology
  • Endosomes / metabolism
  • Exosomes / metabolism*
  • Female
  • Furin / antagonists & inhibitors
  • Furin / physiology
  • Gene Products, env / blood
  • Gene Products, env / physiology*
  • Humans
  • Microscopy, Confocal
  • Minor Histocompatibility Antigens
  • Pre-Eclampsia / blood*
  • Pregnancy
  • Pregnancy Proteins / blood
  • Pregnancy Proteins / deficiency
  • Pregnancy Proteins / physiology*
  • RNA Interference
  • RNA, Small Interfering / pharmacology
  • Symporters
  • Trophoblasts / metabolism*
  • Tumor Suppressor Proteins / antagonists & inhibitors
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / physiology
  • Uterine Neoplasms / pathology


  • Amino Acid Transport System ASC
  • Gene Products, env
  • MFSD2A protein, human
  • Minor Histocompatibility Antigens
  • Pregnancy Proteins
  • RNA, Small Interfering
  • SLC1A5 protein, human
  • Symporters
  • Tumor Suppressor Proteins
  • syncytin
  • syncytin 2 protein, human
  • FURIN protein, human
  • Furin