Interaction of estrogen receptor α with protein kinase C α and c-Src in osteoblasts during differentiation

Bone ◽  
2004 ◽  
Vol 34 (1) ◽  
pp. 100-111 ◽  
Author(s):  
Maurizio Longo ◽  
Marina Brama ◽  
Maria Marino ◽  
Silvia Bernardini ◽  
Kenneth S Korach ◽  
...  
Keyword(s):  
Estrogen Receptor ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Estrogen Receptor Α ◽  
Kinase C

scholarly journals Modulation of human estrogen receptor α F promoter by a protein kinase C/c-Src-dependent mechanism in osteoblast-like cells

2006 ◽  
Vol 37 (3) ◽  
pp. 489-502 ◽  
Author(s):  
Maurizio Longo ◽  
Barbara Peruzzi ◽  
Dario Fortunati ◽  
Veronica De Luca ◽  
Stefanie Denger ◽  
...  
Keyword(s):  
Estrogen Receptor ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Osteoblast Differentiation ◽  
Promoter Activity ◽  
Estrogen Receptor Α ◽  
Luciferase Reporter ◽  
Kinase C ◽  
Human Estrogen Receptor ◽  
Primary Osteoblasts

The human estrogen receptor α (ERα ) gene is driven by multiple promoters, of which the F promoter alone is found to be active in primary osteoblasts. The study was aimed at identifying new regulatory pathways affecting transcription of the receptor in this cell lineage. We generated human osteoblast-like cells, Saos-2, stably transfected with a luciferase-reporter gene downstream of the human ERα F promoter (Saos F-Luc), and assayed the reporter response to differentiation-related signals. Over-confluence, shown to stimulate osteoblast differentiation, caused a time-dependent increase of F-promoter activity and correlated with an inactivation of protein kinase C α (PKCα ). PKC downregulation, obtained by long-term treatment with phorbol 12-myristate 13-acetate (PMA), resulted in promoter stimulation at similar levels in sub-confluent cells. The F promoter contains a putative PMA-responsive AP-1 site, but AP-1 activation was unremarkable in over-confluent cells. Treatment with PP1, a specific inhibitor of the non-receptor tyrosine-kinase c-Src, which is a negative regulator of osteoblast differentiation, showed that the activity of this kinase inhibits the F promoter. In PP1-treated cells, F-promoter activity was not further increased by PMA. Treatment with the generic kinase inhibitor 4-dimethylaminopyridine (DMAP) resulted in a dose-dependent induction of the promoter, which matched a parallel decrease of active c-Src. The effect was c-Src dependent, as DMAP caused no further promoter induction in PP1-treated cells. Overexpression of exogenous human ERα resulted in modest promoter stimulation, which required the ligand-independent activator function 1 of the receptor. In murine primary osteoblasts, additional ERα signal was observed upon induction of F promoter. In conclusion, we demonstrated a robust PKC/c-Src-dependent and estrogen-independent mechanism modulating transcription of ERα in osteoblasts, probably affecting estrogen responsiveness during cell differentiation.

scholarly journals Estrogen receptor-α, RBCK1, and protein kinase C β 1 cooperate to regulate estrogen receptor-α gene expression

2012 ◽  
Vol 49 (3) ◽  
pp. 277-287 ◽  
Author(s):  
Nina Gustafsson Sheppard ◽  
Nina Heldring ◽  
Karin Dahlman-Wright
Keyword(s):  
Breast Cancer ◽  
Estrogen Receptor ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Cancer Cells ◽  
Molecular Mechanism ◽  
Breast Cancer Cells ◽  
Target Genes ◽  
Estrogen Receptor Α ◽  
Kinase C

Estrogen receptor α (ERα) is initially overexpressed in two-thirds of all breast cancers and is involved in its development and proliferation. We previously reported that the RanBP-type and C3HC4-type zinc finger containing 1 (RBCK1) interacts with the ERα promoter and that RBCK1 expression positively correlates with ERα levels, expression of ERα downstream target genes, and proliferation of breast cancer cells. Based on this, and that RBCK1 positively correlates with ERα expression in breast cancer samples, we propose RBCK1 as a potential therapeutic target in breast cancer acting as a modulator of ERα expression. To further explore this, the molecular mechanism by which RBCK1 regulates ERα expression has to be defined. Here, we show that ERα, RBCK1, and the RBCK1-interacting protein protein kinase C β 1 (PKCβI) co-occupy a previously identified ERα binding region in the proximal ERα promoter. We describe a number of mechanistic details of this complex including that RBCK1 recruitment to the ERα promoter B is facilitated by ERα, which in turn facilitates PKCβI recruitment and PKCβI-dependent histone modifications. Furthermore, ERα regulation of its own mRNA expression is facilitated by RBCK1 recruitment, suggesting an ERα coactivator function of RBCK1. The interaction between RBCK1 and ERα was dependent on the E3 ubiquitin ligase domain of RBCK1 and the activating function-1 domain of ERα. The ligand-binding function of ERα does not influence the interaction with RBCK1. In summary, our data provide insight into the molecular mechanism by which ERα expression is modulated in breast cancer cells.

scholarly journals Rapid Signaling of Estrogen in Hypothalamic Neurons Involves a Novel G-Protein-Coupled Estrogen Receptor that Activates Protein Kinase C

2003 ◽  
Vol 23 (29) ◽  
pp. 9529-9540 ◽  
Author(s):  
Jian Qiu ◽  
Martha A. Bosch ◽  
Sandra C. Tobias ◽  
David K. Grandy ◽  
Thomas S. Scanlan ◽  
...  
Keyword(s):  
Estrogen Receptor ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
G Protein ◽  
Hypothalamic Neurons ◽  
Kinase C ◽  
Rapid Signaling ◽  
G Protein Coupled

Gsα, protein kinase C, cathepsin D, growth factors, estrogen receptor-related protein, and p53 in prolactin cell adenomas and null cell adenomas of the pituitary

1998 ◽  
Vol 9 (2) ◽  
pp. 135-148
Author(s):  
Lars Wellhausen ◽  
Wolfgang Saeger ◽  
Wolf Müller ◽  
Michael Derwahl ◽  
Christiane Hamacher ◽  
...  
Keyword(s):  
Estrogen Receptor ◽  
Protein Kinase C ◽  
Growth Factors ◽  
Protein Kinase ◽  
Cathepsin D ◽  
Related Protein ◽  
Null Cell ◽  
Prolactin Cell ◽  
Kinase C ◽  
Null Cell Adenomas

scholarly journals Direct Binding and Activation of Protein Kinase C Isoforms by Aldosterone and 17β-Estradiol

2007 ◽  
Vol 21 (11) ◽  
pp. 2637-2650 ◽  
Author(s):  
Rodrigo Alzamora ◽  
Laura R. Brown ◽  
Brian J. Harvey
Keyword(s):  
Estrogen Receptor ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Steroid Hormones ◽  
Molecular Mechanisms ◽  
Receptor Expression ◽  
C2 Domain ◽  
Kinase C ◽  
Direct Binding ◽  
17Β Estradiol

Abstract Protein kinase C (PKC) is a signal transduction protein that has been proposed to mediate rapid responses to steroid hormones. Previously, we have shown aldosterone directly activates PKCα whereas 17β-estradiol activates PKCα and PKCδ; however, neither the binding to PKCs nor the mechanism of action has been established. To determine the domains of PKCα and PKCδ involved in binding of aldosterone and 17β-estradiol, glutathione S-transferase fusion recombinant PKCα and PKCδ mutants were used to perform in vitro binding assays with [3H]aldosterone and [3H]17β-estradiol. 17β-Estradiol bound both PKCα and PKCδ but failed to bind PKC mutants lacking a C2 domain. Similarly, aldosterone bound only PKCα and mutants containing C2 domains. Thus, the C2 domain is critical for binding of these hormones. Binding affinities for aldosterone and 17β-estradiol were between 0.5–1.0 nM. Aldosterone and 17β-estradiol competed for binding to PKCα, suggesting they share the same binding site. Phorbol 12,13-dybutyrate did not compete with hormone binding; furthermore, they have an additive effect on PKC activity. EC50 for activation of PKCα and PKCδ by aldosterone and 17β-estradiol was approximately 0.5 nM. Immunoblot analysis using a phospho-PKC antibody revealed that upon binding, PKCα and PKCδ undergo autophosphorylation with an EC50 in the 0.5–1.0 nm range. 17β-Estradiol activated PKCα and PKCδ in estrogen receptor-positive and -negative breast cancer cells (MCF-7 and HCC-38, respectively), suggesting estrogen receptor expression is not required for 17β-estradiol-induced PKC activation. The present results provide first evidence for direct binding and activation of PKCα and PKCδ by steroid hormones and the molecular mechanisms involved.

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