Roles of transactivating functions 1 and 2 of estrogen receptor-α in bone

Anna Borjesson, Sara H Windahl, Marie K Lagerquist, Cecilia Engdahl, Baruch Frenkel, Sofia Moverare-Skrtic, Klara Sjogren, Jenny M Kindblom, Alexandra Stubelius, Ulrika Islander, Maria C Antal, Andree Krust, Pierre Chambon, Claes Ohlsson

Research output: Contribution to journalArticlepeer-review

Abstract

The bone-sparing effect of estrogen is primarily mediated via estrogen receptor-α (ERα), which stimulates target gene transcription through two activation functions (AFs), AF-1 in the N-terminal and AF-2 in the ligand binding domain. To evaluate the role of ERα AF-1 and ERα AF-2 for the effects of estrogen in bone in vivo, we analyzed mouse models lacking the entire ERα protein (ERα−/−), ERα AF-1 (ERαAF-10), or ERα AF-2 (ERαAF-20). Estradiol (E2) treatment increased the amount of both trabecular and cortical bone in ovariectomized (OVX) WT mice. Neither the trabecular nor the cortical bone responded to E2 treatment in OVX ERα−/− or OVX ERαAF-20 mice. OVX ERαAF-10 mice displayed a normal E2 response in cortical bone but no E2 response in trabecular bone. Although E2
treatment increased the uterine and liver weights and reduced the thymus weight in OVX WT mice, no effect was seen on these parameters in OVX ERα−/− or OVX ERαAF-20 mice. The effect of E2 in OVX ERαAF-10 mice was tissue-dependent, with no or weak E2 response on thymus and uterine weights but a normal response on liver weight. In conclusion, ERα AF-2 is required for the estrogenic
effects on all parameters evaluated, whereas the role of ERα AF-1 is tissue-specific, with a crucial role in trabecular bone and uterus but not cortical bone. Selective ER modulators stimulating ERα with minimal activation of ERα AF-1 could retain beneficial actions in cortical bone, constituting 80% of the skeleton, while minimizing effects on reproductive organs.
Original languageEnglish
Pages (from-to)6288-6293
Number of pages6
JournalProceedings of the National Academy of Sciences
Volume108
Issue number15
DOIs
Publication statusPublished - 12 Apr 2011

Keywords

  • Estrogen Receptor alpha
  • BONE
  • OSTEOPOROSIS
  • cortical bone
  • CANCELLOUS BONE
  • activation function

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