Sinnett-Smith James, Zhukova Elena, Rey Osvaldo, Rozengurt Enrique
Division of Digestive Diseases, Department of Medicine, School of Medicine, CURE: Digestive Diseases Research Center and Molecular Biology Institute, University of California, Los Angeles, California 90095, USA.
J Cell Physiol. 2007 Jun;211(3):781-90. doi: 10.1002/jcp.20984.
Protein kinase D (PKD) plays an important role in mediating cellular DNA synthesis in response to G protein-coupled receptor (GPCR) agonists but the function of other isoforms of the PKD family has been much less explored. Here, we examined whether PKD2 overexpression in Swiss 3T3 cells facilitates DNA synthesis and the activation of the extracellular regulated protein kinase (ERK) pathway in response to the mitogenic GPCR agonist bombesin. We show that PKD2 overexpression markedly potentiated the ability of this agonist to induce DNA synthesis. Addition of bombesin to Swiss 3T3 cells overexpressing PKD2 also induced a striking increase in the duration of MEK/ERK/RSK activation as compared with cultures of control cells. In contrast, neither DNA synthesis nor the duration of ERK activation in response to epidermal growth factor, which acts via protein kinase C/PKD2-independent pathways, was increased. Furthermore, bombesin promoted a striking accumulation of c-Fos protein in cells overexpressing PKD2. Our study demonstrates that PKD2, like PKD, facilitates mitogenesis and supports the hypothesis that an increase in the duration of the ERK signaling leading to accumulation of immediate gene products is one of the mechanisms by which isoforms of the PKD family enhance re-initiation of DNA synthesis by Gq-coupled receptor activation.
蛋白激酶D（PKD）在介导细胞对G蛋白偶联受体（GPCR）激动剂的DNA合成反应中起重要作用，但PKD家族其他亚型的功能研究较少。在此，我们研究了瑞士3T3细胞中PKD2的过表达是否能促进DNA合成以及响应有丝分裂原性GPCR激动剂蛙皮素时细胞外调节蛋白激酶（ERK）途径的激活。我们发现PKD2的过表达显著增强了该激动剂诱导DNA合成的能力。与对照细胞培养物相比，向过表达PKD2的瑞士3T3细胞中添加蛙皮素也导致MEK/ERK/RSK激活的持续时间显著增加。相反，通过不依赖蛋白激酶C/PKD2的途径起作用的表皮生长因子所诱导的DNA合成或ERK激活的持续时间均未增加。此外，蛙皮素促进了过表达PKD2的细胞中c-Fos蛋白的显著积累。我们的研究表明，PKD2与PKD一样，促进有丝分裂，并支持以下假设：导致即刻早期基因产物积累的ERK信号持续时间增加是PKD家族亚型通过Gq偶联受体激活增强DNA合成重新起始的机制之一。
