Pasteurella Multocida Toxin Prevents Osteoblast Differentiation by Transactivation of the MAP-Kinase Cascade via the Gαq/11 - p63RhoGEF - RhoA Axis
Pasteurella Multocida Toxin Prevents Osteoblast Differentiation by Transactivation of the MAP-Kinase Cascade via the Gαq/11 - p63RhoGEF - RhoA Axis
复制标题
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
作者：
P. Siegert;G. Schmidt;P. Papatheodorou;T. Wieland;K. Aktories;Joachim H. C. Orth
多杀性巴氏杆菌毒素（PMT）是引起多种动物进行性萎缩性鼻炎的主要毒力因子。PMT导致鼻甲骨的破坏，暗示毒素对成骨细胞和/或破骨细胞的影响。该毒素通过脱酰胺化必需的谷氨酰胺残基诱导Gq/11-、G12/13-和Gi-家族的Gα蛋白的组成性活化。为研究PMT对骨细胞的影响，我们采用大鼠颅骨原代成骨细胞和基质ST-2细胞作为分化模型。作为功能性成骨细胞的标志物，测定碱性磷酸酶的表达和活性、矿化结节的形成或特定转录因子如osterix的表达。在这里，我们表明，毒素抑制分化和/或Gαq/11激活成骨细胞的功能。随后，Gαq/11通过p63 RhoGEF激活RhoA，p63 RhoGEF特异性地与Gαq/11相互作用，但不与其他G蛋白如Gα12/13和Gαi相互作用。活化的RhoA通过Rho激酶反式激活丝裂原活化蛋白（MAP）激酶级联，涉及Ras、MEK和ERK，导致成骨细胞分化的抑制。PMT诱导的分化抑制对于成骨细胞系是选择性的，因为ST-2细胞的脂肪细胞样分化没有受到阻碍。目前的工作提供了新的见解，细菌毒素PMT如何通过激活Gαq/11-家族的异源三聚体G蛋白来控制成骨细胞的发育，并且是理解毒素在由多杀性巴氏杆菌引起的进行性萎缩性鼻炎期间骨丢失中的作用的分子发病机制基础。
The 146-kDa Pasteurella multocida toxin (PMT) is the main virulence factor to induce P. multocida-associated progressive atrophic rhinitis in various animals. PMT leads to a destruction of nasal turbinate bones implicating an effect of the toxin on osteoblasts and/or osteoclasts. The toxin induces constitutive activation of Gα proteins of the Gq/11-, G12/13- and Gi-family by deamidating an essential glutamine residue. To study the PMT effect on bone cells, we used primary osteoblasts derived from rat calvariae and stromal ST-2 cells as differentiation model. As marker of functional osteoblasts the expression and activity of alkaline phosphatase, formation of mineralization nodules or expression of specific transcription factors as osterix was determined. Here, we show that the toxin inhibits differentiation and/or function of osteoblasts by activation of Gαq/11. Subsequently, Gαq/11 activates RhoA via p63RhoGEF, which specifically interacts with Gαq/11 but not with other G proteins like Gα12/13 and Gαi. Activated RhoA transactivates the mitogen-activated protein (MAP) kinase cascade via Rho kinase, involving Ras, MEK and ERK, resulting in inhibition of osteoblast differentiation. PMT-induced inhibition of differentiation was selective for the osteoblast lineage as adipocyte-like differentiation of ST-2 cells was not hampered. The present work provides novel insights, how the bacterial toxin PMT can control osteoblastic development by activating heterotrimeric G proteins of the Gαq/11-family and is a molecular pathogenetic basis for understanding the role of the toxin in bone loss during progressive atrophic rhinitis induced by Pasteurella multocida.
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影响因子：
56.9
作者：
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通讯作者：
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影响因子：
56.9
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