Noncanonical G-Protein-Dependent Modulation of Osteoclast Differentiation and Bone Resorption Mediated by Pasteurella multocida Toxin
Noncanonical G-Protein-Dependent Modulation of Osteoclast Differentiation and Bone Resorption Mediated by Pasteurella multocida Toxin
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多杀性巴氏杆菌毒素介导的非经典 G 蛋白依赖性破骨细胞分化和骨吸收调节
作者：
Strack J;Heni H;Gilsbach R;Hein L;Aktories K;Orth JH
多杀性巴氏杆菌毒素（Pasteurella multocida toxin，PMT）在动物中诱导萎缩性鼻炎，其特征在于鼻甲骨的降解，表明毒素对骨细胞如成骨细胞和破骨细胞的作用。PMT的潜在分子机制被定义为通过特定谷氨酰胺残基的脱酰胺化持续激活异源三聚体G蛋白。在这里，我们表明，PMT直接作用于破骨细胞前体细胞，如骨髓来源的CD 14+单核细胞和RAW246.7细胞，以诱导破骨细胞生成，通过表达破骨细胞特异性标志物，如抗酒石酸酸性磷酸酶和骨吸收活性。仅用PMT进行的治疗刺激破骨细胞分化，显示毒素的核因子-κB配体（RANKL）受体激活剂非依赖性作用。潜在的信号转导途径被定义为异源三聚体G蛋白Gαq/11的激活导致Ras的反式激活和丝裂原活化蛋白激酶途径。Gαq/11通过其效应物磷脂酶Cβ蛋白激酶C（PKC）（包括富含脯氨酸的酪氨酸激酶2（Pyk 2））反式激活Ras。PMT诱导的丝裂原活化蛋白激酶途径活化导致破骨细胞生成转录因子AP-1、NF-κB和NFATc 1的刺激。此外，NFAT的Ca 2+依赖性钙调神经磷酸酶激活对于PMT诱导的破骨细胞生成至关重要。这些数据不仅阐明了萎缩性鼻炎中PMT依赖性骨丢失的基本原理，G蛋白依赖的骨吸收途径，与RANKL-RANK途径不同，但与RANKL-RANK途径相似。我们将异源三聚体G蛋白定义为在破骨细胞成熟过程中被低估的实体/参与者，这可能具有药理学意义。重要信息多杀性巴氏杆菌毒素（PMT）引起鼻甲骨退化，导致萎缩性鼻炎综合征。近年来，PMT的分子机制和底物特异性得到了进一步的研究。该毒素通过共价修饰激活异源三聚体G蛋白。然而，PMT诱导骨降解的机制知之甚少。我们的报告表明，PMT对破骨细胞前体细胞的直接影响，导致骨降解破骨细胞的成熟。有趣的是，PMT独立于细胞因子RANKL刺激破骨细胞生成，RANKL是诱导破骨细胞分化的关键因素。这暗示了PMT诱导的非经典破骨细胞生成信号通路。已阐明的Gαq/11依赖性破骨细胞生成信号转导通路终止于破骨细胞生成NFAT信号转导。非典型的异源三聚体G蛋白依赖性破骨细胞分化过程可能具有药理学相关性，因为该途径的成员是高度可药用的。特别是，G蛋白偶联受体活性的调节破骨细胞祖细胞的小分子可能是特别感兴趣的。
Pasteurella multocida toxin (PMT) induces atrophic rhinitis in animals, which is characterized by a degradation of nasal turbinate bones, indicating an effect of the toxin on bone cells such as osteoblasts and osteoclasts. The underlying molecular mechanism of PMT was defined as a persistent activation of heterotrimeric G proteins by deamidation of a specific glutamine residue. Here, we show that PMT acts directly on osteoclast precursor cells such as bone marrow-derived CD14+monocytes and RAW246.7 cells to induce osteoclastogenesis as measured by expression of osteoclast-specific markers such as tartrate-resistant acid phosphatase and bone resorption activity. Treatment performed solely with PMT stimulates osteoclast differentiation, showing a receptor activator of nuclear factor-κB ligand (RANKL)-independent action of the toxin. The underlying signal transduction pathway was defined as activation of the heterotrimeric G proteins Gαq/11leading to the transactivation of Ras and the mitogen-activated protein kinase pathway. Gαq/11transactivates Ras via its effector phospholipase Cβ-protein kinase C (PKC) involving proline-rich tyrosine kinase 2 (Pyk2). PMT-induced activation of the mitogen-activated protein kinase pathway results in stimulation of the osteoclastogenic transcription factors AP-1, NF-κB, and NFATc1. In addition, Ca2+-dependent calcineurin activation of NFAT is crucial for PMT-induced osteoclastogenesis. The data not only elucidate a rationale for PMT-dependent bone loss during atrophic rhinitis but also highlight a noncanonical, G-protein-dependent pathway toward bone resorption that is distinct from the RANKL-RANK pathway but mimics it. We define heterotrimeric G proteins as as-yet-underestimated entities/players in the maturation of osteoclasts which might be of pharmacological relevance.IMPORTANCEPasteurella multocida toxin (PMT) induces degradation of nasal turbinate bones, leading to the syndrome of atrophic rhinitis. Recently, the molecular mechanism and substrate specificity of PMT were identified. The toxin activates heterotrimeric G proteins by a covalent modification. However, the mechanism by which PMT induces bone degradation is poorly understood. Our report demonstrates a direct effect of PMT on osteoclast precursor cells, leading to maturation of bone-degrading osteoclasts. Interestingly, PMT stimulates osteoclastogenesis independently of the cytokine RANKL, which is a key factor in induction of osteoclast differentiation. This implicates a noncanonical osteoclastogenic signaling pathway induced by PMT. The elucidated Gαq/11-dependent osteoclastogenic signal transduction pathway ends in osteoclastogenic NFAT signaling. The noncanonical, heterotrimeric G protein-dependent osteoclast differentiation process may be of pharmacological relevance, as members of this pathway are highly druggable. In particular, modulation of G protein-coupled receptor activity in osteoclast progenitors by small molecules might be of specific interest.
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多杀性巴氏杆菌毒素通过 Gαq/11 - p63RhoGEF - RhoA 轴反式激活 MAP 激酶级联来防止成骨细胞分化
影响因子：
6.7
作者：
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通讯作者：
Joachim H. C. Orth
DOI：
10.1073/pnas.0902743106
发表时间：
2009-09-22
影响因子：
11.1
作者：
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通讯作者：
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影响因子：
2.4
作者：
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通讯作者：
K. Pedersen
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影响因子：
2.2
作者：
M. D. de Jong;J. Nielsen
通讯作者：
J. Nielsen
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影响因子：
4.1
作者：
M. Bélv
通讯作者：
M. Bélv