Exp Clin Endocrinol Diabetes 2005; 113 - 139
DOI: 10.1055/s-2005-862998

Influence of retinoic acid on post-translational modifications of a-enolase in the human follicular thyroid carcinoma cell line FTC-133

B Trojanowicz 1, A Winkler 1, K Hammje 1, Z Chen 1, C Sekulla 1, D Glanz 2, C Schmutzler 3, B Mentrup 3, S Hombach-Klonisch 4, T Klonisch 4, R Finke 5, J Köhrle 3, H Dralle 1, C Hoang-Vu 1
  • 1Universitätsklinik und Poliklinik für Allgemein-, Viszeral- und Gefäßchirurgie, Halle (Saale)
  • 2Institut für Physiologische Chemie, Halle (Saale)
  • 3Institut für Experimentelle Endokrinologie, Berlin
  • 4University of Manitoba, Winnipeg, Manitoba, Canada
  • 5Universitätsklinik und Poliklinik für Kinderchirurgie, Halle (Saale)

Enolases (2-phospho-D-glycerate hydrolases) are glycolytic enzymes that catalyse the interconversion of 2-phosphoglycerate to phosphoenolpyruvate, may also be involved in cellular differentiation. In this study we investigated the influence of retinoic acid (RA) on the proteome, the 48 kDa human α-enolase (ENO1) and its post-translational modifications in the follicular thyroid carcinoma cell line FTC-133.

FTC 133 cells was cultured in DMEM/F12, stimulated with 1µM RA for 24h and 72h. Total RNA for RT-PCR was obtained using Trizol. For two dimensional (2D) gel analyses, total protein was extracted with either lysis buffer A (8M Urea, 4% CHAPS, 1% DTT, 0.8% Pharmalyte) or lysis buffer B (7M Urea, 2M Thiourea, 4% CHAPS, 2% Pharmalyte, 2% DTT) for standard 2D gel electrophoresis and silver staining gels or 2D fluorescence difference gel electrophoresis (DIGE), respectively. Spots were isolated and prepared for mass spectrometry (MALDI-Tof MS and MS/MS) analyses.

RT-PCR showed no significant differences in ENO1 mRNA expression. Western blot and 2D gel analyses revealed RA-mediated up-regulation of ENO1 protein production. In addition, eleven not yet determined protein spots were up-regulated upon RA treatment. ENO1 was identified and sequenced using tandem mass spectrometry (MS/MS). Modification mapping revealed that RA induced dephosphorylation of tyrosine236 and threonine237 but phosphorylation of serine349 and threonine351. In contrast to controls, RA induced deacetylation of peptides in positions 328–330 IAK and 404–406 LAK, whereas residue methionine368 was acetylated. No changes were observed in ENO1 glycolysation upon RA treatment. RA induced calcium- and phospholipide-independent kinases. Phosphoprotein staining showed that RA affected the phosphorylation status in FTC-133.

Our data show that RA increases the number of protein spots, ENO1 protein expression level and induces changes in the phosphorylation and acetylation of ENO1. The biological significance of de-/phosphorylation and de-/acetylation of the ENO1 in FTC-133 cells still requires clarification.