Acute expression of RET/PTC induces isozyme-specific activation and subsequent downregulation of PKCepsilon in PCCL3 thyroid cells.
Acute expression of RET/PTC induces isozyme-specific activation and subsequent downregulation of PKCepsilon in PCCL3 thyroid cells.
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RET/PTC 的急性表达诱导 PCCL3 甲状腺细胞中同工酶特异性激活和随后 PKCepsilon 的下调。
DOI：
10.1038/sj.onc.1206829
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发表时间：
2003
期刊：
影响因子：
8
通讯作者：
Fagin,JamesA
中科院分区：
文献类型：
--
作者：
Knauf,JeffreyA;Ouyang,Bin;Croyle,Mickey;Kimura,Edna;Fagin,JamesA
大多数甲状腺乳头状癌具有同工酶特异性的蛋白激酶Cɛ还原，这种还原是通过转录后机制发生的。在这里，我们测试癌蛋白Ret/PtC是否可能对这种效应起作用，因为Ret/PtC重排在PtC中相当普遍，并且Ret/Ptc激活了Pkcs的上游调节因子PLCγ。在诱导Ret/Ptc1或Ret/PtC3表达后3h，有明显的PKCɛ活化。由于ɛ/PTC的急性表达并不改变PCCL3细胞中表达的其他PKC同工酶的亚细胞分布，因此激活仅限于PKC同工酶。延长Ret/Ptc的表达时间(2-6天)可引起蛋白激酶Cɛ亚细胞定位的同工酶特异性改变和总蛋白激酶Cɛ水平的降低。RET/PTC3Y541F的表达不与PLCγ相互作用，但通过其他RET效应器正常传递信号，在所研究的任何时间点对PKCɛ的分布都没有影响。然而，Ret/PTC Y541F的表达仅能部分阻止总的PKCɛ水平的下调。随着Ret/ɛ表达时间的延长，PKC基因表达降低的细胞对阿霉素诱导的细胞凋亡具有相对的抵抗力。根据我们先前的观察，表达显性负性PKCɛ的PCCL3细胞也具有明显的抗凋亡能力，我们认为在延长RET/PTC激活时间后选择性下调PKCɛ可促进细胞存活和克隆性扩增。
Most papillary thyroid carcinomas (PTC) have an isozyme-specific reduction of protein kinase C (PKC) ɛ, which occurs through a post-transcriptional mechanism. Here, we test whether the oncoprotein RET/PTC could be responsible for this effect, since RET/PTC rearrangements are quite prevalent in PTC and RET/PTC activates PLCγ, an upstream modulator of PKCs. At 3 h after induction of RET/PTC1 or RET/PTC3 expression, there was evidence of PKCɛ activation. Activation was restricted to PKCɛ, as acute expression of RET/PTC did not change the subcellular distribution of other PKC isozymes expressed in PCCL3 cells. Prolonged RET/PTC expression (2–6 days) produced an isozyme-specific change in PKCɛ subcellular localization and a decrease in total PKCɛ levels. The expression of RET/PTC3 Y541F, which does not interact with PLCγ, but signals normally through other RET effectors, had no effect on PKCɛ distribution at any of the time points examined. However, downregulation of total PKCɛ levels was only partially prevented by expression of RET/PTC Y541F. Cells with decreased PKCɛ following prolonged expression of RET/PTC were relatively resistant to doxorubicin-induced apoptosis. Based on our previous observation that PCCL3 cells expressing a dominant-negative PKCɛ are also markedly resistant to apoptosis, we propose that selective downregulation of PKCɛ following prolonged RET/PTC activation promotes cell survival and clonal expansion.