Fima E, Shahaf G, Hershko T, Apte R N, Livneh E
Department of Microbiology and Immunology, Faculty of Health Sciences, Ben Gurion University, Beer Sheva 84105, Israel.
Eur Cytokine Netw. 1999 Dec;10(4):491-500.
Protein kinase C encodes a family of enzymes implicated in cellular differentiation, growth control and tumor promotion. The generation and characterization of NIH-3T3 cells which stably overexpress the PKCeta isoform has been previously described by us. In these cells, overexpression of PKCeta altered the expression of specific cell cycle regulators and promoted differentiation [20]. Since PKC has been implicated in the regulation of gene expression, including that of various cytokines, we examined the production of several cytokines in these cells. We report here that out of the major pro-inflammatory cytokines examined, IL-1alpha, IL-1beta, TNF-alpha and IL-6, only IL-6 was generated and secreted in PKCeta -expressing cells without any additional inducer in serum-supplemented cultures (10% FCS). IL-6 was not detected in the control cell line, transfected with the same vector, but lacking the cDNA coding for PKCeta. Moreover, the production of IL-6 on serum stimulation correlated with the levels of PKCeta expressed in these cells. This implies that factors in the serum activate PKCeta and induce IL-6 production. We have examined several growth factors and cytokines for their ability to induce IL-6 production in our PKCeta-expressing cells. Among the growth factors tested (EGF, PDGF, FGF, insulin, IGF-1 and IL-1), PDGF and FGF were the most potent IL-6 inducers. The effects of FGF and PDGF on IL-6 production were blocked in the presence of PKC inhibitors. We also examined the signaling pathways that mediate production of IL-6 in PKCeta-expressing cells. Using specific inhibitors of the MAPK pathway, we have shown a role for ERK and p38 MAPK in FGF- and serum-stimulated IL-6 production, but only for p38 MAPK in PDGF-stimulated IL-6 production. Our studies provide evidence that PDGF and FGF can serve as upstream regulators of PKCeta and that PKCeta is involved in the expression of IL-6. This suggests that inhibition of PKC may provide a basis for the development of drugs for the treatment of disorders in which IL-6 is pathologically involved.
蛋白激酶C编码一族与细胞分化、生长控制及肿瘤促进相关的酶。我们之前已描述过稳定过表达PKCeta亚型的NIH-3T3细胞的产生及特性。在这些细胞中，PKCeta的过表达改变了特定细胞周期调节因子的表达并促进了分化[20]。由于PKC已被认为参与基因表达的调控，包括各种细胞因子的表达调控，我们检测了这些细胞中几种细胞因子的产生情况。我们在此报告，在所检测的主要促炎细胞因子中，即白细胞介素-1α、白细胞介素-1β、肿瘤坏死因子-α和白细胞介素-6，在添加血清（10%胎牛血清）的培养物中，无任何额外诱导剂的情况下，表达PKCeta的细胞中仅产生并分泌了白细胞介素-6。在转染相同载体但缺乏编码PKCeta的cDNA的对照细胞系中未检测到白细胞介素-6。此外，血清刺激时白细胞介素-6的产生与这些细胞中PKCeta的表达水平相关。这意味着血清中的因子激活PKCeta并诱导白细胞介素-6的产生。我们检测了几种生长因子和细胞因子在我们的表达PKCeta的细胞中诱导白细胞介素-6产生的能力。在所检测的生长因子（表皮生长因子、血小板衍生生长因子、成纤维细胞生长因子、胰岛素、胰岛素样生长因子-1和白细胞介素-1）中，血小板衍生生长因子和成纤维细胞生长因子是最有效的白细胞介素-6诱导剂。在存在PKC抑制剂的情况下，成纤维细胞生长因子和血小板衍生生长因子对白细胞介素-6产生的作用被阻断。我们还检测了介导表达PKCeta的细胞中白细胞介素-6产生的信号通路。使用丝裂原活化蛋白激酶（MAPK）途径的特异性抑制剂，我们已表明细胞外信号调节激酶（ERK）和p38 MAPK在成纤维细胞生长因子和血清刺激的白细胞介素-6产生中起作用，但在血小板衍生生长因子刺激的白细胞介素-6产生中仅p38 MAPK起作用。我们的研究提供了证据，表明血小板衍生生长因子和成纤维细胞生长因子可作为PKCeta的上游调节因子，且PKCeta参与白细胞介素-6的表达。这表明抑制PKC可能为开发治疗白细胞介素-6病理参与的疾病的药物提供基础。
