Regulation of protein expression and function of octn2 in forskolin-induced syncytialization in BeWo Cells

Placenta. 2009 Feb;30(2):187-94. doi: 10.1016/j.placenta.2008.11.016. Epub 2008 Dec 16.

Abstract

Placental OCTN2 is a high-affinity carnitine transporter that can interact with a number of therapeutic agents. The process of syncytialization is associated with the expression of a variety of genes. However, the association between syncytialization and OCTN2 expression is not yet clear. Given that forskolin induces BeWo cells to undergo biochemical and morphological differentiation, the purpose of the present study was to investigate whether the function and expression of OCTN2 are influenced by forskolin treatment during syncytialization. The forskolin-induced differentiation of BeWo cells was validated by secretion of beta-human chorionic gonadotropin (beta-hCG) and syncytin expression. Cellular localization of OCTN2 was analyzed by confocal microscopy. Expression of OCTN2 and the modular proteins PDZK1, PDZK2, NHERF1 and NHERF2 was analyzed by Western blotting and carnitine uptake by BeWo cells was estimated and the kinetic properties of uptake measured. The results showed that forskolin treatment increased beta-hCG secretion and syncytin expression, suggesting induction of syncytialization. Confocal images of BeWo cells showed the localization of OCTN2 in the brush-border membrane. OCTN2 protein expression was upregulated in isolated brush-border membranes by long-term forskolin treatment, but the V(m) for carnitine uptake was unchanged, although the K(m) increased. PDZK1, NHERF1 and NHERF2 protein expression in the brush-border membrane was downregulated by forskolin treatment, whereas PDZK2 levels remained unchanged. In conclusion, protein expression and function of OCTN2 in BeWo cells can be regulated by forskolin treatment. While the presence of forskolin results in an increase in OCTN2 protein expression, the increase in uptake capacity may be compensated by the decreased expression of PDZK1, NHERF1 or NHERF2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cell Line, Tumor
  • Cell Transformation, Neoplastic
  • Choriocarcinoma / pathology
  • Chorionic Gonadotropin, beta Subunit, Human / metabolism
  • Colforsin / pharmacology*
  • Gene Expression Regulation / drug effects
  • Gene Products, env / genetics
  • Gene Products, env / metabolism
  • Giant Cells / drug effects*
  • Giant Cells / metabolism
  • Humans
  • Membrane Proteins
  • Microvilli / drug effects
  • Microvilli / metabolism
  • Organic Cation Transport Proteins / genetics
  • Organic Cation Transport Proteins / metabolism*
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism
  • Pregnancy Proteins / genetics
  • Pregnancy Proteins / metabolism
  • Sodium-Hydrogen Exchangers / genetics
  • Sodium-Hydrogen Exchangers / metabolism
  • Solute Carrier Family 22 Member 5
  • Trophoblasts / drug effects*
  • Trophoblasts / metabolism
  • Trophoblasts / pathology

Substances

  • Carrier Proteins
  • Chorionic Gonadotropin, beta Subunit, Human
  • Gene Products, env
  • Membrane Proteins
  • Organic Cation Transport Proteins
  • PDZK1 protein, human
  • Phosphoproteins
  • Pregnancy Proteins
  • SLC22A5 protein, human
  • Sodium-Hydrogen Exchangers
  • Solute Carrier Family 22 Member 5
  • sodium-hydrogen exchanger regulatory factor
  • syncytin
  • Colforsin