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SAT-520 The Effects Of AKAP13 On Osteogenesis By Modulation Of RhoA And Wnt Signaling

[Introduction] AKAP13 (Protein Kinase A Anchoring Protein 13) is a guanine nucleotides exchange factor (GEF) that activates RhoA as well as a scaffold protein integrating multiple signaling cascades. Previous study has shown that Akap13 hetero knockout mice develop osteoporotic changes and result in...

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Autores principales: Ishida, Akiko, Nakayama, Akitoshi, Koide, Hisashi, Tatsuno, Ichiro, Tanaka, Tomoaki, Yokote, Kotaro
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Endocrine Society 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6552077/
http://dx.doi.org/10.1210/js.2019-SAT-520
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author Ishida, Akiko
Nakayama, Akitoshi
Koide, Hisashi
Tatsuno, Ichiro
Tanaka, Tomoaki
Yokote, Kotaro
author_facet Ishida, Akiko
Nakayama, Akitoshi
Koide, Hisashi
Tatsuno, Ichiro
Tanaka, Tomoaki
Yokote, Kotaro
author_sort Ishida, Akiko
collection PubMed
description [Introduction] AKAP13 (Protein Kinase A Anchoring Protein 13) is a guanine nucleotides exchange factor (GEF) that activates RhoA as well as a scaffold protein integrating multiple signaling cascades. Previous study has shown that Akap13 hetero knockout mice develop osteoporotic changes and result in decreased osteogenesis and we believe AKAP13 is involved in the early stages of osteogenesis. On the other hand, the involvement of Wnt signaling in bone metabolism has been extensively studied, however the detailed mechanism has not been elucidated. Recent study showed that focal adhesion kinase (FAK)-integrin contributes to bone formation via Wnt signaling pathway. Thus, it is suggested that Akap13 may influence osteogenesis via Wnt signaling through FAK mediated integrin pathway that is linked to Rho GTPase. In this study, we investigated the involvement of AKAP13 in bone formation and the relationship with Wnt signaling. [Methods] uCT analyses of femurs of Akap13 heterozygous-conventional knock-out mice were performed. We transfected the Akap13 or control siRNA into osteoblastic cells and examined the Wnt-related genes expression and osteogenic markers by real time RT-PCR. Osteogenic marker expression was examined after application of RhoA expression vector with or without Akap13 siRNA to osteoblastic cells. [Results] Mice haploinsufficient for Akap13 (Akap13+/-) displayed reduced bone mineral density resembling the changes observed in osteoporotic bone. Colony forming unit-fibroblast numbers were diminished in Akap13+/- mice. Osteoblast numbers in periosteum and extracellular matrix production in Akap13+/- mice was reduced compared to control littermates. Runx2 and Alp mRNAs were both reduced in femora of Akap13+/- mice. Akap13 knockdown showed a significant decrease of Lef1 mRNA expression in MC3T3-E1 cells as well as a reduction of Runx2 and ALP mRNA expression in immortalized bone marrow stem cells (BMSCs). RhoA overexpression in BMSCs showed Alp mRNA increment in RhoA induction dose dependent manner. Reduction of Alp mRNA by AKAP13 knockdown was amplified in higher RhoA overexpression. [Discussion] The Akap13 knockdown showed decreased expression of Wnt-related genes in osteoblastic cells, suggesting the possibility that AKAP13 plays an important role in regulating osteogenesis through Wnt signaling. AKAP13 may be involved in or contribute directly to Wnt signaling through interaction with RhoA by mechanical stress or stimulation of extracellular matrix.<!--EndFragment-->
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spelling pubmed-65520772019-06-13 SAT-520 The Effects Of AKAP13 On Osteogenesis By Modulation Of RhoA And Wnt Signaling Ishida, Akiko Nakayama, Akitoshi Koide, Hisashi Tatsuno, Ichiro Tanaka, Tomoaki Yokote, Kotaro J Endocr Soc Bone and Mineral Metabolism [Introduction] AKAP13 (Protein Kinase A Anchoring Protein 13) is a guanine nucleotides exchange factor (GEF) that activates RhoA as well as a scaffold protein integrating multiple signaling cascades. Previous study has shown that Akap13 hetero knockout mice develop osteoporotic changes and result in decreased osteogenesis and we believe AKAP13 is involved in the early stages of osteogenesis. On the other hand, the involvement of Wnt signaling in bone metabolism has been extensively studied, however the detailed mechanism has not been elucidated. Recent study showed that focal adhesion kinase (FAK)-integrin contributes to bone formation via Wnt signaling pathway. Thus, it is suggested that Akap13 may influence osteogenesis via Wnt signaling through FAK mediated integrin pathway that is linked to Rho GTPase. In this study, we investigated the involvement of AKAP13 in bone formation and the relationship with Wnt signaling. [Methods] uCT analyses of femurs of Akap13 heterozygous-conventional knock-out mice were performed. We transfected the Akap13 or control siRNA into osteoblastic cells and examined the Wnt-related genes expression and osteogenic markers by real time RT-PCR. Osteogenic marker expression was examined after application of RhoA expression vector with or without Akap13 siRNA to osteoblastic cells. [Results] Mice haploinsufficient for Akap13 (Akap13+/-) displayed reduced bone mineral density resembling the changes observed in osteoporotic bone. Colony forming unit-fibroblast numbers were diminished in Akap13+/- mice. Osteoblast numbers in periosteum and extracellular matrix production in Akap13+/- mice was reduced compared to control littermates. Runx2 and Alp mRNAs were both reduced in femora of Akap13+/- mice. Akap13 knockdown showed a significant decrease of Lef1 mRNA expression in MC3T3-E1 cells as well as a reduction of Runx2 and ALP mRNA expression in immortalized bone marrow stem cells (BMSCs). RhoA overexpression in BMSCs showed Alp mRNA increment in RhoA induction dose dependent manner. Reduction of Alp mRNA by AKAP13 knockdown was amplified in higher RhoA overexpression. [Discussion] The Akap13 knockdown showed decreased expression of Wnt-related genes in osteoblastic cells, suggesting the possibility that AKAP13 plays an important role in regulating osteogenesis through Wnt signaling. AKAP13 may be involved in or contribute directly to Wnt signaling through interaction with RhoA by mechanical stress or stimulation of extracellular matrix.<!--EndFragment--> Endocrine Society 2019-04-30 /pmc/articles/PMC6552077/ http://dx.doi.org/10.1210/js.2019-SAT-520 Text en Copyright © 2019 Endocrine Society https://creativecommons.org/licenses/by-nc-nd/4.0/ This article has been published under the terms of the Creative Commons Attribution Non-Commercial, No-Derivatives License (CC BY-NC-ND; https://creativecommons.org/licenses/by-nc-nd/4.0/).
spellingShingle Bone and Mineral Metabolism
Ishida, Akiko
Nakayama, Akitoshi
Koide, Hisashi
Tatsuno, Ichiro
Tanaka, Tomoaki
Yokote, Kotaro
SAT-520 The Effects Of AKAP13 On Osteogenesis By Modulation Of RhoA And Wnt Signaling
title SAT-520 The Effects Of AKAP13 On Osteogenesis By Modulation Of RhoA And Wnt Signaling
title_full SAT-520 The Effects Of AKAP13 On Osteogenesis By Modulation Of RhoA And Wnt Signaling
title_fullStr SAT-520 The Effects Of AKAP13 On Osteogenesis By Modulation Of RhoA And Wnt Signaling
title_full_unstemmed SAT-520 The Effects Of AKAP13 On Osteogenesis By Modulation Of RhoA And Wnt Signaling
title_short SAT-520 The Effects Of AKAP13 On Osteogenesis By Modulation Of RhoA And Wnt Signaling
title_sort sat-520 the effects of akap13 on osteogenesis by modulation of rhoa and wnt signaling
topic Bone and Mineral Metabolism
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6552077/
http://dx.doi.org/10.1210/js.2019-SAT-520
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