RAS-DEPENDENT SIGNAL-TRANSDUCTION IS INDISPENSABLE BUT NOT SUFFICIENT FOR THE ACTIVATION OF AP1/JUN BY PKC-DELTA
RAS-DEPENDENT SIGNAL-TRANSDUCTION IS INDISPENSABLE BUT NOT SUFFICIENT FOR THE ACTIVATION OF AP1/JUN BY PKC-DELTA
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DOI：
10.1002/j.1460-2075.1994.tb06517.x
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发表时间：
1994-05-15
期刊：
影响因子：
11.4
通讯作者：
OHNO, S
中科院分区：
文献类型：
--
作者：
HIRAI, S;IZUMI, Y;OHNO, S
12-O-十四烷酰佛波醇-13-乙酸酯 (TPA) 对基因表达的调节被认为是由蛋白激酶 C (PKC)（TPA 的主要细胞受体）介导的。我们通过证明 PKC δ 的过度表达增强了 NHI3T3 细胞中 TRE-tk-CAT 报告基因的 TPA 诱导来证实了这一点。为了研究 PKC δ 和 Ras 依赖性信号转导途径与 TRE 结合转录因子 AP1/Jun 之间的相互关系，我们构建了 PKC δ 的组成型活性和显性失活突变体。激活的 Ras 与过表达的 c-Jun 或 JunD 协同诱导报告基因表达，并且这种诱导对显性失活 PKC δ 不敏感。另一方面，由组成型活性 PKC δ 诱导的报告基因表达受到显性失活 Ras 以及显性失活 PKC δ 的严重抑制。因此，Ras 激活对于 PKC delta 激活 AP1/Jun 来说是必不可少的。然而，在没有过表达的 cJun 或 JunD 的情况下，激活的 Ras 明显不如组成型活性 PKC δ 有效，后者显示报告基因表达完全激活。这表明 PKC delta 下游存在一条额外的、不依赖于 Ras 的信号通路来激活 AP1/Jun。尽管组成型活性 PKC δ 具有激活 TRE-tk-CAT 表达的显着能力，但该突变体抑制了细胞生长。
Modulation of gene expression by 12-O-tetradecanoylphorbol-13-acetate (TPA) is thought to be mediated by protein kinase C (PKC), a major cellular receptor for TPA. We confirm this by showing that the overexpression of PKC delta enhances the TPA induction of the TRE-tk-CAT reporter gene in NHI3T3 cells. To investigate the mutual relationship between PKC delta- and Ras-dependent signal transduction pathways to a TRE binding transcription factor, AP1/Jun, we constructed constitutively active and dominant negative mutants of PKC delta. Activated Ras induced reporter gene expression in collaboration with overexpressed c-Jun or JunD, and this induction was insensitive to the dominant negative PKC delta. On the other hand, reporter gene expression induced by the constitutively active PKC delta was severely inhibited by dominant negative Ras, as well as by the dominant negative PKC delta. Thus, Ras activation must be indispensable for PKC delta to activate AP1/Jun. In the absence of overexpressed cJun or JunD, activated Ras was, however, clearly less effective than constitutively active PKC delta which showed full activation of reporter gene expression by itself. This suggests the presence of an additional, Ras-independent, signaling pathway downstream of PKC delta to activate AP1/Jun. In spite of the remarkable ability of constitutively active PKC delta to activate TRE-tk-CAT expression, this mutant suppressed cell growth.