Bcl2 deficiency activates FoxO through Akt inactivation and accelerates osteoblast differentiation.
Bcl2 deficiency activates FoxO through Akt inactivation and accelerates osteoblast differentiation.
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DOI：
10.1371/journal.pone.0086629
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Komori T
中科院分区：
文献类型：
--
作者：
Moriishi T;Kawai Y;Komori H;Rokutanda S;Eguchi Y;Tsujimoto Y;Asahina I;Komori T
成骨细胞凋亡在骨骼发育和维持中起着重要作用，是性类固醇缺乏、糖皮质激素过量和衰老导致骨质疏松的部分原因。虽然Bcl2亚家族蛋白，包括Bcl2和Bcl-XL，抑制细胞凋亡，但Bcl2在成骨细胞分化中的生理意义尚未完全阐明。为了研究这一点，我们检测了Bcl2缺陷（Bcl2−/−）小鼠。在Bcl2 - / -小鼠中，溴脱氧尿苷（BrdU）阳性的成骨细胞数量减少，而末端脱氧核苷酸转移酶介导的dUTP缺口末端标记（TUNEL）阳性的成骨细胞数量增加。出乎意料的是，Bcl2 - / -小鼠的成骨细胞分化加速，骨钙素阳性成骨细胞早期出现。在体外培养过程中，为了最大限度地减少细胞凋亡对细胞密度的影响，高浓度的原代成骨细胞也可以加速成骨细胞的分化。FoxO转录因子的活性受Akt的磷酸化负调控，在细胞增殖、死亡、分化、寿命和应激反应等多种细胞事件中发挥重要作用。受FoxOs调控的FasL、Gadd45a、Bim表达上调；FoxOs的表达和活性增强；在Bcl2−/−calvariae中Akt和FoxO1、FoxO3a的磷酸化水平降低。此外，p53 mRNA和蛋白水平升高，抑制Akt活化的p53靶基因Pten和Igfbp3的表达在Bcl2−/−calvariae中上调。然而，Pten而非Igfbp3在Bcl2−/−原代成骨细胞中上调，p53诱导Pten而非Igfbp3体外表达。FoxO1或FoxO3a的沉默抑制了FoxO3a的组成性活性，增强了成骨细胞的分化。这些发现表明，Bcl2缺乏通过Akt失活诱导和激活FoxOs，至少在一定程度上，通过p53上调Pten的表达，FoxOs的表达和活性增强可能是Bcl2 - / -小鼠成骨细胞分化加速的原因之一。
Osteoblast apoptosis plays an important role in bone development and maintenance, and is in part responsible for osteoporosis in sex steroid deficiency, glucocorticoid excess, and aging. Although Bcl2 subfamily proteins, including Bcl2 and Bcl-XL, inhibit apoptosis, the physiological significance of Bcl2 in osteoblast differentiation has not been fully elucidated. To investigate this, we examined Bcl2-deficient (Bcl2−/−) mice. In Bcl2−/− mice, bromodeoxyuridine (BrdU)-positive osteoblasts were reduced in number, while terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive osteoblasts were increased. Unexpectedly, osteoblast differentiation was accelerated in Bcl2−/− mice as shown by the early appearance of osteocalcin-positive osteoblasts. Osteoblast differentiation was also accelerated in vitro when primary osteoblasts were seeded at a high concentration to minimize the reduction of the cell density by apoptosis during culture. FoxO transcription factors, whose activities are negatively regulated through the phosphorylation by Akt, play important roles in multiple cell events, including proliferation, death, differentiation, longevity, and stress response. Expressions of FasL, Gadd45a, and Bim, which are regulated by FoxOs, were upregulated; the expression and activity of FoxOs were enhanced; and the phosphorylation of Akt and that of FoxO1 and FoxO3a by Akt were reduced in Bcl2−/− calvariae. Further, the levels of p53 mRNA and protein were increased, and the expression of p53-target genes, Pten and Igfbp3 whose proteins inhibit Akt activation, was upregulated in Bcl2−/− calvariae. However, Pten but not Igfbp3 was upregulated in Bcl2−/− primary osteoblasts, and p53 induced Pten but not Igfbp3 in vitro. Silencing of either FoxO1 or FoxO3a inhibited and constitutively-active FoxO3a enhanced osteoblast differentiation. These findings suggest that Bcl2 deficiency induces and activates FoxOs through Akt inactivation, at least in part, by upregulating Pten expression through p53 in osteoblasts, and that the enhanced expression and activities of FoxOs may be one of the causes of accelerated osteoblast differentiation in Bcl2−/− mice.
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影响因子：
29
作者：
Ambrogini E;Almeida M;Martin-Millan M;Paik JH;Depinho RA;Han L;Goellner J;Weinstein RS;Jilka RL;O'Brien CA;Manolagas SC
通讯作者：
Manolagas SC
影响因子：
3.9
作者：
Lam, E. W-F.;Francis, R. E.;Petkovic, M.
通讯作者：
Petkovic, M.
影响因子：
64.8
作者：
BUCKBINDER, L;TALBOTT, R;KLEY, N
通讯作者：
KLEY, N
影响因子：
2.5
作者：
Maruyama, Zenjiro;Yoshida, Carolina A.;Komori, Toshihisa
通讯作者：
Komori, Toshihisa
影响因子：
15.9
作者：
Jilka, RL;Weinstein, RS;Manolagas, SC
通讯作者：
Manolagas, SC