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Reduction of protein phosphatase 2A Cα promotes in vivo bone formation and adipocyte differentiation
Kaya Yoshida1, Jumpei Teramachi2, Kenta Uchibe3
1Department of Oral Healthcare Educations, 3-18-15, Kuramoto, Tokushima 770-8504, Japan.
Abstract:
Serine/threonine protein phosphatase 2A (PP2A) regulates diverse physiological processes such as cell cycle, growth, apoptosis, and signal transduction. Previously, we demonstrated that silencing of the α-isoform of PP2A catalytic subunit (PP2A Cα) in osteoblasts accelerated osteoblast differentiation, whereas its overexpression suppressed differentiation. In this study, we examined the role of PP2A Cα in in vivo bone formation by generating transgenic mice (PP2A-Tg), in which the dominant negative form of PP2A Cα was specifically expressed in osteoblasts. PP2A-Tg mice exhibited an increase in body weight, cortical bone mineral density, and cortical bone thickness. Interestingly, they also displayed higher amounts of adipose tissue in the bone marrow of tibiae. The co-culture study showed that PP2A Cα-knockdown osteoblasts stimulated adipocyte differentiation from undifferentiated mesenchymal cells via upregulation of the adipocyte marker genes, such as peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer binding protein α (C/EBPα). These results indicated that the reduction of PP2A Cα levels in osteoblasts promoted bone formation in vivo. Additionally, PP2A Cα in osteoblasts was also potentially involved in controlling adipocyte differentiation through a paracrine mechanism.
Insights
Reducing Serine/threonine protein phosphatase 2A catalytic subunit alpha (PP2A Cα) in osteoblasts enhances bone formation in vivo. This involves promoting osteoblast differentiation and potentially influencing adipocyte differentiation via paracrine signaling.
Area of Science:
- Biochemistry
- Cell Biology
- Bone Biology
Background:
- Serine/threonine protein phosphatase 2A (PP2A) is crucial for various cellular processes.
- The α-isoform of the PP2A catalytic subunit (PP2A Cα) plays a role in osteoblast differentiation.
- Previous studies showed PP2A Cα influences osteoblast differentiation in vitro.
Purpose of the Study:
- To investigate the in vivo role of PP2A Cα in osteoblast differentiation and bone formation.
- To determine the effect of PP2A Cα manipulation in osteoblasts on overall bone health.
- To explore the potential paracrine mechanisms by which PP2A Cα affects bone marrow adiposity.
Main Methods:
- Generation of transgenic mice (PP2A-Tg) expressing a dominant-negative form of PP2A Cα in osteoblasts.
- Analysis of bone mineral density, cortical bone thickness, and body weight in PP2A-Tg mice.
- Co-culture experiments to assess the effect of PP2A Cα-knockdown osteoblasts on adipocyte differentiation.
Main Results:
- PP2A-Tg mice showed increased body weight, cortical bone mineral density, and cortical bone thickness.
- Increased adipose tissue was observed in the bone marrow of PP2A-Tg mice tibiae.
- Knockdown of PP2A Cα in osteoblasts stimulated adipocyte differentiation, upregulating PPARγ and C/EBPα.
Conclusions:
- Reduced PP2A Cα levels in osteoblasts promote in vivo bone formation.
- Osteoblast-derived PP2A Cα may regulate bone marrow adipocyte differentiation through paracrine signaling.
- Targeting PP2A Cα in osteoblasts represents a potential strategy for enhancing bone formation.