LEFTY2/endometrial bleeding-associated factor up-regulates Na+ Coupled Glucose Transporter SGLT1 expression and Glycogen Accumulation in Endometrial Cancer Cells

PLoS One. 2020 Apr 1;15(4):e0230044. doi: 10.1371/journal.pone.0230044. eCollection 2020.

Abstract

LEFTY2 (endometrial bleeding associated factor; EBAF or LEFTYA), a cytokine released shortly before menstrual bleeding, is a negative regulator of cell proliferation and tumour growth. LEFTY2 down-regulates Na+/H+ exchanger activity with subsequent inhibition of glycolytic flux and lactate production in endometrial cancer cells. Glucose can be utilized not only for glycolysis but also for glycogen formation. Both glycolysis and glycogen formation require cellular glucose uptake which could be accomplished by the Na+ coupled glucose transporter-1 (SGLT1; SLC5A1). The present study therefore explored whether LEFTY2 modifies endometrial SGLT1 expression and activity as well as glycogen formation. Ishikawa and HEC1a cells were exposed to LEFTY2, SGLT1 and glycogen synthase (GYS1) transcript levels determined by qRT-PCR. SGLT1, GYS1 and phospho-GYS1 protein abundance was quantified by western blotting, cellular glucose uptake from 2-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)Amino)-2-Deoxyglucose (2-NBDG) uptake, and cellular glycogen content utilizing an enzymatic assay and subsequent colorimetry. As a result, a 48-hour treatment with LEFTY2 significantly increased SGLT1 and GYS1 transcript levels as well as SGLT1 and GYS1 protein abundance in both Ishikawa and HEC1a cells. 2-NBDG uptake and cellular glycogen content were upregulated significantly in Ishikawa (type 1) but not in type 2 endometrial HEC1a cells, although there was a tendency of increased 2-NBDG uptake. Further, none of the effects were seen in human benign endometrial cells (HESCs). Interestingly, in both Ishikawa and HEC1a cells, a co-treatment with TGF-β reduced SGLT1, GYS and phospho-GYS protein levels, and thus reduced glycogen levels and again HEC1a cells had no significant change. In conclusion, LEFTY2 up-regulates expression and activity of the Na+ coupled glucose transporter SGLT1 and glycogen synthase GYS1 in a cell line specific manner. We further show the treatment with LEFTY2 fosters cellular glucose uptake and glycogen formation and TGF-β can negate this effect in endometrial cancer cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line, Tumor
  • Endometrial Neoplasms / metabolism*
  • Endometrium / metabolism*
  • Female
  • Glucose / metabolism
  • Glycogen / metabolism*
  • Glycogen Synthase / metabolism*
  • Humans
  • Left-Right Determination Factors / physiology*
  • Sodium / metabolism
  • Sodium-Glucose Transporter 1 / metabolism*

Substances

  • LEFTY2 protein, human
  • Left-Right Determination Factors
  • SLC5A1 protein, human
  • Sodium-Glucose Transporter 1
  • Glycogen
  • Sodium
  • Glycogen Synthase
  • Glucose

Grants and funding

This work was supported by funding to M.S.S the Zukunftskonzept award (Deutsche Forschungsgemeinschaft; ZUK63), the IZKF (2510-0-0) and the Margarete von Wrangell-Habilitationsprogramm für Frauen (31-7635.41/118/3; Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg). We acknowledge support by Deutsche Forschungsgemeinschaft and Open Access Publishing Fund of the University of Tübingen. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.