蛋白激酶C对100 kDa 2-5A合成酶的特异性调控。

Specific regulation of the 100 kDa 2-5 A synthetase by protein kinase C.

作者信息

Raber J, Eldar H, Lehrer R, Chebath J, Livneh E

机构信息

Department of Molecular Genetics and Virology, Weizmann Institute of Science, Rehovot, Israel.

出版信息

Eur Cytokine Netw. 1991 Aug-Sep;2(4):281-90.

PMID:1756233

Abstract

The 2-5 A synthetase is a system of several isozymes, whose expression is induced by interferons (IFNs) at the transcriptional level. These enzymes mediate part of the antiviral effects of IFNs and are thought to have an important role in cell growth or differentiation. The different isozymes -100, 69, 46 and 40 kDa expressed in human cells, or the 105, 71 and 43 kDa expressed in mouse cells--are induced by IFNs with cell type specificity, and exhibit individual differences in their biochemical and enzymatic properties. Here we studied the effects of the tumor promoter phorbol ester (TPA), or the calcium ionophore A23187, on the pattern of expression of 2-5 A synthetase isoforms, and found a role of protein kinase C (PKC) in the adjustments of this pattern. We show that in HeLa cells the 100 kDa 2-5 A synthetase can be specifically induced by short term treatments with TPA, or with the calcium ionophore A23187. Induction of the 100 kDa form is mainly post-transcriptional. By contrast long term treatments by TPA resulting in the down regulation of PKC, or employing H7, a specific PKC inhibitor, reduced drastically the induction by IFNs of the 100 kDa enzyme in HeLa or fibroblast cells, without reducing the expression of the other forms. Moreover, using a mouse Swiss 3T3 cell line in which the cDNA coding for PKC-alpha was introduced, leading to its overexpression, we could show that the mouse 105 kDa synthetase was constitutively expressed. Thus, a direct correlation was found between the expression of PKC-alpha and the specific induction of the 105 kDa form. Neutralization of autocrine IFNs by antibodies reduces the expression of the 105 kDa species. However the autocrine IFN in the medium of the cells overexpressing PKC is not able to induce 2-5 A synthetase in control transfected Swiss 3T3 cells. Thus, IFN is probably essential for the expression of the 105 kDa synthetase but may be not produced in sufficient amounts to induce the 105 kDa protein.

摘要

2-5A合成酶是一个由多种同工酶组成的系统，其表达在转录水平上由干扰素（IFN）诱导。这些酶介导IFN的部分抗病毒作用，并且被认为在细胞生长或分化中起重要作用。在人类细胞中表达的不同同工酶——100、69、46和40 kDa，或在小鼠细胞中表达的105、71和43 kDa——由IFN以细胞类型特异性诱导，并且在其生化和酶学性质上表现出个体差异。在这里，我们研究了肿瘤启动子佛波酯（TPA）或钙离子载体A23187对2-5A合成酶同工型表达模式的影响，并发现蛋白激酶C（PKC）在这种模式的调节中起作用。我们表明，在HeLa细胞中，100 kDa的2-5A合成酶可以通过用TPA或钙离子载体A23187进行短期处理而被特异性诱导。100 kDa形式的诱导主要是转录后水平的。相比之下，TPA的长期处理导致PKC下调，或使用特异性PKC抑制剂H7，可显著降低HeLa或成纤维细胞中IFN对100 kDa酶的诱导，而不降低其他形式的表达。此外，使用导入了编码PKC-α的cDNA从而导致其过表达的小鼠瑞士3T3细胞系，我们可以表明小鼠105 kDa合成酶是组成性表达的。因此，发现PKC-α的表达与105 kDa形式的特异性诱导之间存在直接相关性。用抗体中和自分泌IFN会降低105 kDa种类的表达。然而，过表达PKC的细胞培养基中的自分泌IFN不能在对照转染的瑞士3T3细胞中诱导2-5A合成酶。因此，IFN可能对105 kDa合成酶的表达至关重要，但可能产生的量不足以诱导105 kDa蛋白。