Regulation of retinoic acid receptor α by protein kinase C in B16 mouse melanoma cells
Regulation of retinoic acid receptor α by protein kinase C in B16 mouse melanoma cells
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DOI：
10.1074/jbc.m201185200
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发表时间：
2002-07-19
影响因子：
4.8
通讯作者：
Niles, RM
中科院分区：
文献类型：
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作者：
Boskovic, G;Desai, D;Niles, RM
我们之前发现视黄酸可以刺激 B16 小鼠黑色素瘤细胞中蛋白激酶 Cα (PKC) 的表达。由于据报道 PKC 可以磷酸化视黄酸受体 (RAR) 并改变其功能，因此我们确定 PKC 水平和/或活性的变化是否会影响 B16 黑色素瘤中 RAR 的表达或功能。使用体内磷酸化和带移位技术，我们无法证明改变 PKC 活性和/或蛋白质水平会改变 RARα 的体内磷酸化。然而，PKC 的激活导致 RARα 蛋白增加。受体蛋白的增加与佛波二丁酸刺激的受体激活功能 2 (AF-2) 依赖性转录活性的增加相关。酶抑制剂和显性失活 PKC 的使用表明，RARα 的升高需要酶活性。 PKC 介导的 RARα 增加是由于该蛋白质的半衰期增加了 2.5 倍。相反，PKC 的下调会缩短 RARalpha 蛋白的半衰期，并显着抑制 AF-2 依赖性转录活性。 PKC 的下调还抑制了 RAR 与视黄酸反应元件的结合以及视黄酸对 RARbeta 表达的诱导。这些发现表明 PKC 可以通过改变 RAR 蛋白的稳定性来影响视黄酸信号传导，而不直接磷酸化该受体。
We have previously found that retinoic acid stimulates the expression of protein kinase Calpha (PKC) in B16 mouse melanoma cells. Because it has been reported that PKC can phosphorylate retinoic acid receptor (RAR) and alter its function, we determined whether changes in the level and/or activity of PKC could affect the expression or function of the RAR in B16 melanoma. Using in vivo phosphorylation and band shift techniques, we could not demonstrate that altering PKC activity and/or protein level changed the in vivo phosphorylation of RARalpha. However activation of PKC resulted in increased RARalpha protein. Increased receptor protein correlated with a phorbol dibutyrate-stimulated increase in receptor activation function-2 (AF-2)-dependent transcriptional activity. Use of enzyme inhibitors and dominant-negative PKCs indicated that enzyme activity was required for elevation in the RARalpha. The PKC-mediated increase in RARalpha was due to a 2.5-fold increase in the half-life of this protein. In contrast, the down-regulation of PKC diminished RARalpha protein half-life and markedly inhibited AF-2-dependent transcriptional activity. The down-regulation of PKC also inhibited the binding of RAR to a retinoic acid response element and the retinoic acid induction of RARbeta expression. These findings suggest that PKC can influence retinoic acid signaling by altering the stability of RAR protein without directly phosphorylating this receptor.