Estrogen enhances αvβ3 integrin expression by avian osteoclast precursors via stabilization of β3 integrin mRNA

Cheng Fu Li, F. Patrick Ross, Xu Cao, Steven L. Teitelbaum

Research output: Contribution to journalArticle

Abstract

Although bone resorption is accelerated with menopause, the means by which diminished circulating 17β-estradiol (E2) promotes osteoclastic activity are unknown. We hypothesized that since the integrin αvβ3 is essential to the resorptive process, reduced E2 levels may increase the integrin's expression by osteoclast precursors. Thus, avian osteoclast precursors (known to contain E2 receptors) were exposed ± E2, surface iodinated, and lysed. The lysate was immunoprecipitated with an antibody recognizing the intact αvβ3 heterodimer. We find E2 alone fails to impact on αvβ3 expression. Most importantly, however, picomolar (i.e. post-menopausal), but not nanomolar (i.e. premenopausal) concentrations of E2, when added in conjunction with 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], enhance αvβ3 expression on the plasma membrane of avian osteoclast precursors relative to 1,25-(OH)2D3 alone. Induction of αvβ3 by picomolar levels of E2 is dose-dependent, maximizing at 10-11-10-12 M, wherein the sex steroid enhances 1,25-(OH)2-D3-stimulated integrin expression approximately 2.5-fold. Northern analysis reveals that β3 mRNA levels parallel those of αV3. E2 (10-12 M) increases expression of β3 mRNA induced by a range of 1,25-(OH)2D3 concentrations extending from 10-10 M-10-8 M. The E2 + 1,25-(OH)2D3 additive effect on β3 mRNA appears as early as 1 day of treatment and progresses for at least 3 days. Consistent with evidence that the β3 subunit regulates heterodimer expression, the sex steroid does not impact αv mRNA. Attesting to the specificity of E2 on β3 mRNA expression, the steroid does not impact on β5 mRNA, and its stereoisomer, 17αE2, is inactive in these experiments. Likewise, E2 has no effect on retinoic acid-induced stimulation of β3 mRNA levels. While 1,25-(OH)2D3 induction of β3 mRNA reflects transcriptional activation, nuclear run-on studies indicate that, despite its inductive effect on β3 mRNA levels, E2 does not alter β3 gene transcription. Transcriptional arrest experiments demonstrate the t1/2 of β3 mRNA derived from 1,25-(OH)2D3-treated cells cultured in the presence or absence of 10-8 M E2 is approximately 4 h. On the other hand, 10-12 M E2, in conjunction with 1,25-(OH)2D3, more than triples stability of β3 message. Thus, in conjunction with 1,25-(OH)2D3, E2, at levels circulating in postmenopausal (but not premenopausal) females, in whom the rate of bone resorption is accelerated, up-regulates, post-transcriptionally, in osteoclast precursors, αvβ3, an integrin heterodimer pivotal to the resorptive process.

Original languageEnglish (US)
Pages (from-to)805-813
Number of pages9
JournalMolecular Endocrinology
Volume9
Issue number7
StatePublished - Jul 1995
Externally publishedYes

Fingerprint

Osteoclasts
Integrins
Estrogens
Messenger RNA
Steroids
Bone Resorption
Stereoisomerism
Calcitriol
Menopause
Tretinoin
Transcriptional Activation
Estradiol
Cultured Cells
Up-Regulation
Cell Membrane
Antibodies

ASJC Scopus subject areas

  • Molecular Biology
  • Endocrinology, Diabetes and Metabolism

Cite this

Estrogen enhances αvβ3 integrin expression by avian osteoclast precursors via stabilization of β3 integrin mRNA. / Li, Cheng Fu; Ross, F. Patrick; Cao, Xu; Teitelbaum, Steven L.

In: Molecular Endocrinology, Vol. 9, No. 7, 07.1995, p. 805-813.

Research output: Contribution to journalArticle

Li, Cheng Fu ; Ross, F. Patrick ; Cao, Xu ; Teitelbaum, Steven L. / Estrogen enhances αvβ3 integrin expression by avian osteoclast precursors via stabilization of β3 integrin mRNA. In: Molecular Endocrinology. 1995 ; Vol. 9, No. 7. pp. 805-813.
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abstract = "Although bone resorption is accelerated with menopause, the means by which diminished circulating 17β-estradiol (E2) promotes osteoclastic activity are unknown. We hypothesized that since the integrin αvβ3 is essential to the resorptive process, reduced E2 levels may increase the integrin's expression by osteoclast precursors. Thus, avian osteoclast precursors (known to contain E2 receptors) were exposed ± E2, surface iodinated, and lysed. The lysate was immunoprecipitated with an antibody recognizing the intact αvβ3 heterodimer. We find E2 alone fails to impact on αvβ3 expression. Most importantly, however, picomolar (i.e. post-menopausal), but not nanomolar (i.e. premenopausal) concentrations of E2, when added in conjunction with 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], enhance αvβ3 expression on the plasma membrane of avian osteoclast precursors relative to 1,25-(OH)2D3 alone. Induction of αvβ3 by picomolar levels of E2 is dose-dependent, maximizing at 10-11-10-12 M, wherein the sex steroid enhances 1,25-(OH)2-D3-stimulated integrin expression approximately 2.5-fold. Northern analysis reveals that β3 mRNA levels parallel those of αV3β3. E2 (10-12 M) increases expression of β3 mRNA induced by a range of 1,25-(OH)2D3 concentrations extending from 10-10 M-10-8 M. The E2 + 1,25-(OH)2D3 additive effect on β3 mRNA appears as early as 1 day of treatment and progresses for at least 3 days. Consistent with evidence that the β3 subunit regulates heterodimer expression, the sex steroid does not impact αv mRNA. Attesting to the specificity of E2 on β3 mRNA expression, the steroid does not impact on β5 mRNA, and its stereoisomer, 17αE2, is inactive in these experiments. Likewise, E2 has no effect on retinoic acid-induced stimulation of β3 mRNA levels. While 1,25-(OH)2D3 induction of β3 mRNA reflects transcriptional activation, nuclear run-on studies indicate that, despite its inductive effect on β3 mRNA levels, E2 does not alter β3 gene transcription. Transcriptional arrest experiments demonstrate the t1/2 of β3 mRNA derived from 1,25-(OH)2D3-treated cells cultured in the presence or absence of 10-8 M E2 is approximately 4 h. On the other hand, 10-12 M E2, in conjunction with 1,25-(OH)2D3, more than triples stability of β3 message. Thus, in conjunction with 1,25-(OH)2D3, E2, at levels circulating in postmenopausal (but not premenopausal) females, in whom the rate of bone resorption is accelerated, up-regulates, post-transcriptionally, in osteoclast precursors, αvβ3, an integrin heterodimer pivotal to the resorptive process.",
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N2 - Although bone resorption is accelerated with menopause, the means by which diminished circulating 17β-estradiol (E2) promotes osteoclastic activity are unknown. We hypothesized that since the integrin αvβ3 is essential to the resorptive process, reduced E2 levels may increase the integrin's expression by osteoclast precursors. Thus, avian osteoclast precursors (known to contain E2 receptors) were exposed ± E2, surface iodinated, and lysed. The lysate was immunoprecipitated with an antibody recognizing the intact αvβ3 heterodimer. We find E2 alone fails to impact on αvβ3 expression. Most importantly, however, picomolar (i.e. post-menopausal), but not nanomolar (i.e. premenopausal) concentrations of E2, when added in conjunction with 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], enhance αvβ3 expression on the plasma membrane of avian osteoclast precursors relative to 1,25-(OH)2D3 alone. Induction of αvβ3 by picomolar levels of E2 is dose-dependent, maximizing at 10-11-10-12 M, wherein the sex steroid enhances 1,25-(OH)2-D3-stimulated integrin expression approximately 2.5-fold. Northern analysis reveals that β3 mRNA levels parallel those of αV3β3. E2 (10-12 M) increases expression of β3 mRNA induced by a range of 1,25-(OH)2D3 concentrations extending from 10-10 M-10-8 M. The E2 + 1,25-(OH)2D3 additive effect on β3 mRNA appears as early as 1 day of treatment and progresses for at least 3 days. Consistent with evidence that the β3 subunit regulates heterodimer expression, the sex steroid does not impact αv mRNA. Attesting to the specificity of E2 on β3 mRNA expression, the steroid does not impact on β5 mRNA, and its stereoisomer, 17αE2, is inactive in these experiments. Likewise, E2 has no effect on retinoic acid-induced stimulation of β3 mRNA levels. While 1,25-(OH)2D3 induction of β3 mRNA reflects transcriptional activation, nuclear run-on studies indicate that, despite its inductive effect on β3 mRNA levels, E2 does not alter β3 gene transcription. Transcriptional arrest experiments demonstrate the t1/2 of β3 mRNA derived from 1,25-(OH)2D3-treated cells cultured in the presence or absence of 10-8 M E2 is approximately 4 h. On the other hand, 10-12 M E2, in conjunction with 1,25-(OH)2D3, more than triples stability of β3 message. Thus, in conjunction with 1,25-(OH)2D3, E2, at levels circulating in postmenopausal (but not premenopausal) females, in whom the rate of bone resorption is accelerated, up-regulates, post-transcriptionally, in osteoclast precursors, αvβ3, an integrin heterodimer pivotal to the resorptive process.

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