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Endogenous protein kinase-C activation in osteoblast-like cells modulates responsiveness to estrogen and estrogen receptor levels.

Publication ,  Journal Article
Migliaccio, S; Wetsel, WC; Fox, WM; Washburn, TF; Korach, KS
Published in: Mol Endocrinol
September 1993

The osteoblast-like osteosarcoma cell line ROS 17/2.8, which expresses very low levels of estrogen receptor (ER), was stably transfected with the mouse ER in order to more easily evaluate the physiological role of estrogens in bone cell homeostasis. These transfected ROS.SMER 14 cells are highly responsive to estrogenic stimulation at subconfluence, but become refractory to estrogenic stimulation when postconfluency is reached. The purpose of these studies was to determine the mechanisms underlying this loss of responsiveness in these ER stably transfected cells at postconfluence. When proliferative capacity was evaluated by bromodeoxyuridine immunocytochemistry, approximately 70% of the subconfluent cells were actively dividing, whereas none of the postconfluent cells underwent division. Subconfluent cells were found to contain 2500-3000 ER-binding sites/cell, whereas the ER in postconfluent cells was low and often undetectable. Steady state ER mRNA levels were not significantly modified by postconfluency. ER protein levels were also unaffected by confluency status. Since protein kinase-C (PKC) has been reported to influence cell proliferation and steroid hormone receptor binding, PKC activity was measured in sub- and postconfluent cells. Calcium-dependent PKC activity was approximately about 2-fold higher in postconfluent compared to subconfluent cells, whereas no differences were discerned in calcium-independent PKC activity. In an effort to examine the role of PKC in greater detail, postconfluent cells were treated with PKC inhibitors (H-7 or staurosporine) or with the tumor promoter TPA (12-O-tetradecanoylphorbol-13-acetate) to down-regulate PKC activity, and changes in ER were evaluated. Inhibition or down-regulation of the PKC activity in postconfluent cells enhanced ER-binding capacity in a dose-dependent manner and estrogen responsiveness of an exogenous reporter gene and of the endogenous alkaline phosphatase, representing an endogenous estrogen-stimulated gene. These data indicate that there is an interaction between the PKC and ER signaling systems in bone cells and that this interaction may be influenced by the proliferative and/or differentiative state of the cells, resulting in modulation of hormone responsiveness.

Duke Scholars

Published In

Mol Endocrinol

DOI

ISSN

0888-8809

Publication Date

September 1993

Volume

7

Issue

9

Start / End Page

1133 / 1143

Location

United States

Related Subject Headings

  • Tumor Cells, Cultured
  • Transfection
  • Tetradecanoylphorbol Acetate
  • Staurosporine
  • Receptors, Estrogen
  • RNA, Messenger
  • Protein Kinase C
  • Piperazines
  • Osteosarcoma
  • Osteoblasts
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Migliaccio, S., Wetsel, W. C., Fox, W. M., Washburn, T. F., & Korach, K. S. (1993). Endogenous protein kinase-C activation in osteoblast-like cells modulates responsiveness to estrogen and estrogen receptor levels. Mol Endocrinol, 7(9), 1133–1143. https://doi.org/10.1210/mend.7.9.8247015
Migliaccio, S., W. C. Wetsel, W. M. Fox, T. F. Washburn, and K. S. Korach. “Endogenous protein kinase-C activation in osteoblast-like cells modulates responsiveness to estrogen and estrogen receptor levels.Mol Endocrinol 7, no. 9 (September 1993): 1133–43. https://doi.org/10.1210/mend.7.9.8247015.
Migliaccio S, Wetsel WC, Fox WM, Washburn TF, Korach KS. Endogenous protein kinase-C activation in osteoblast-like cells modulates responsiveness to estrogen and estrogen receptor levels. Mol Endocrinol. 1993 Sep;7(9):1133–43.
Migliaccio, S., et al. “Endogenous protein kinase-C activation in osteoblast-like cells modulates responsiveness to estrogen and estrogen receptor levels.Mol Endocrinol, vol. 7, no. 9, Sept. 1993, pp. 1133–43. Pubmed, doi:10.1210/mend.7.9.8247015.
Migliaccio S, Wetsel WC, Fox WM, Washburn TF, Korach KS. Endogenous protein kinase-C activation in osteoblast-like cells modulates responsiveness to estrogen and estrogen receptor levels. Mol Endocrinol. 1993 Sep;7(9):1133–1143.

Published In

Mol Endocrinol

DOI

ISSN

0888-8809

Publication Date

September 1993

Volume

7

Issue

9

Start / End Page

1133 / 1143

Location

United States

Related Subject Headings

  • Tumor Cells, Cultured
  • Transfection
  • Tetradecanoylphorbol Acetate
  • Staurosporine
  • Receptors, Estrogen
  • RNA, Messenger
  • Protein Kinase C
  • Piperazines
  • Osteosarcoma
  • Osteoblasts