Phlpp1 is induced by estrogen in osteoclasts and its loss in Ctsk-expressing cells does not protect against ovariectomy-induced bone loss.

Prior studies demonstrated that deletion of the protein phosphatase Phlpp1 in Ctsk-Cre expressing cells enhances bone mass, characterized by diminished osteoclast activity and increased coupling to bone formation. Due to non-specific expression of Ctsk-Cre, the definitive mechanism for this observat...

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Autores principales:	Marcelline K Hanson, Ismael Y Karkache, David H H Molstad, Andrew A Norton, Kim C Mansky, Elizabeth W Bradley
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/a1676eb44dfb4341bb44d713ce62da0b
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spelling	oai:doaj.org-article:a1676eb44dfb4341bb44d713ce62da0b2021-12-02T20:05:20ZPhlpp1 is induced by estrogen in osteoclasts and its loss in Ctsk-expressing cells does not protect against ovariectomy-induced bone loss.1932-620310.1371/journal.pone.0251732https://doaj.org/article/a1676eb44dfb4341bb44d713ce62da0b2021-01-01T00:00:00Zhttps://doi.org/10.1371/journal.pone.0251732https://doaj.org/toc/1932-6203Prior studies demonstrated that deletion of the protein phosphatase Phlpp1 in Ctsk-Cre expressing cells enhances bone mass, characterized by diminished osteoclast activity and increased coupling to bone formation. Due to non-specific expression of Ctsk-Cre, the definitive mechanism for this observation was unclear. To further define the role of bone resorbing osteoclasts, we performed ovariectomy (Ovx) and Sham surgeries on Phlpp1 cKOCtsk and WT mice. Micro-CT analyses confirmed enhanced bone mass of Phlpp1 cKOCtsk Sham females. In contrast, Ovx induced bone loss in both groups, with no difference between Phlpp1 cKOCtsk and WT mice. Histomorphometry demonstrated that Ovx mice lacked differences in osteoclasts per bone surface, suggesting that estradiol (E2) is required for Phlpp1 deficiency to have an effect. We performed high throughput unbiased transcriptional profiling of Phlpp1 cKOCtsk osteoclasts and identified 290 differentially expressed genes. By cross-referencing these differentially expressed genes with all estrogen response element (ERE) containing genes, we identified IGFBP4 as potential estrogen-dependent target of Phlpp1. E2 induced PHLPP1 expression, but reduced IGFBP4 levels. Moreover, genetic deletion or chemical inhibition of Phlpp1 was correlated with IGFBP4 levels. We then assessed IGFBP4 expression by osteoclasts in vivo within intact 12-week-old females. Modest IGFBP4 immunohistochemical staining of TRAP+ osteoclasts within WT females was observed. In contrast, TRAP+ bone lining cells within intact Phlpp1 cKOCtsk females robustly expressed IGFBP4, but levels were diminished within TRAP+ bone lining cells following Ovx. These results demonstrate that effects of Phlpp1 conditional deficiency are lost following Ovx, potentially due to estrogen-dependent regulation of IGFBP4.Marcelline K HansonIsmael Y KarkacheDavid H H MolstadAndrew A NortonKim C ManskyElizabeth W BradleyPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 16, Iss 6, p e0251732 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Marcelline K Hanson Ismael Y Karkache David H H Molstad Andrew A Norton Kim C Mansky Elizabeth W Bradley Phlpp1 is induced by estrogen in osteoclasts and its loss in Ctsk-expressing cells does not protect against ovariectomy-induced bone loss.
description	Prior studies demonstrated that deletion of the protein phosphatase Phlpp1 in Ctsk-Cre expressing cells enhances bone mass, characterized by diminished osteoclast activity and increased coupling to bone formation. Due to non-specific expression of Ctsk-Cre, the definitive mechanism for this observation was unclear. To further define the role of bone resorbing osteoclasts, we performed ovariectomy (Ovx) and Sham surgeries on Phlpp1 cKOCtsk and WT mice. Micro-CT analyses confirmed enhanced bone mass of Phlpp1 cKOCtsk Sham females. In contrast, Ovx induced bone loss in both groups, with no difference between Phlpp1 cKOCtsk and WT mice. Histomorphometry demonstrated that Ovx mice lacked differences in osteoclasts per bone surface, suggesting that estradiol (E2) is required for Phlpp1 deficiency to have an effect. We performed high throughput unbiased transcriptional profiling of Phlpp1 cKOCtsk osteoclasts and identified 290 differentially expressed genes. By cross-referencing these differentially expressed genes with all estrogen response element (ERE) containing genes, we identified IGFBP4 as potential estrogen-dependent target of Phlpp1. E2 induced PHLPP1 expression, but reduced IGFBP4 levels. Moreover, genetic deletion or chemical inhibition of Phlpp1 was correlated with IGFBP4 levels. We then assessed IGFBP4 expression by osteoclasts in vivo within intact 12-week-old females. Modest IGFBP4 immunohistochemical staining of TRAP+ osteoclasts within WT females was observed. In contrast, TRAP+ bone lining cells within intact Phlpp1 cKOCtsk females robustly expressed IGFBP4, but levels were diminished within TRAP+ bone lining cells following Ovx. These results demonstrate that effects of Phlpp1 conditional deficiency are lost following Ovx, potentially due to estrogen-dependent regulation of IGFBP4.
format	article
author	Marcelline K Hanson Ismael Y Karkache David H H Molstad Andrew A Norton Kim C Mansky Elizabeth W Bradley
author_facet	Marcelline K Hanson Ismael Y Karkache David H H Molstad Andrew A Norton Kim C Mansky Elizabeth W Bradley
author_sort	Marcelline K Hanson
title	Phlpp1 is induced by estrogen in osteoclasts and its loss in Ctsk-expressing cells does not protect against ovariectomy-induced bone loss.
title_short	Phlpp1 is induced by estrogen in osteoclasts and its loss in Ctsk-expressing cells does not protect against ovariectomy-induced bone loss.
title_full	Phlpp1 is induced by estrogen in osteoclasts and its loss in Ctsk-expressing cells does not protect against ovariectomy-induced bone loss.
title_fullStr	Phlpp1 is induced by estrogen in osteoclasts and its loss in Ctsk-expressing cells does not protect against ovariectomy-induced bone loss.
title_full_unstemmed	Phlpp1 is induced by estrogen in osteoclasts and its loss in Ctsk-expressing cells does not protect against ovariectomy-induced bone loss.
title_sort	phlpp1 is induced by estrogen in osteoclasts and its loss in ctsk-expressing cells does not protect against ovariectomy-induced bone loss.
publisher	Public Library of Science (PLoS)
publishDate	2021
url	https://doaj.org/article/a1676eb44dfb4341bb44d713ce62da0b
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Phlpp1 is induced by estrogen in osteoclasts and its loss in Ctsk-expressing cells does not protect against ovariectomy-induced bone loss.

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