Activation of protein kinase G increases the expression of p21CIP1, p27KIP1, and Histidine triad protein 1 through Sp1
Activation of protein kinase G increases the expression of p21CIP1, p27KIP1, and Histidine triad protein 1 through Sp1
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DOI：
10.1158/0008-5472.can-07-6869
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发表时间：
2008-07-01
期刊：
影响因子：
11.2
通讯作者：
Weinstein, I. Bernard
中科院分区：
文献类型：
--
作者：
Cen, Bo;Deguchi, Atsuko;Weinstein, I. Bernard
环鸟苷3 '，5'-单磷酸（cGMP）依赖性蛋白激酶G（PKG）的抗癌作用已引起相当大的兴趣，但其潜在机制尚未完全建立。在这项研究中，我们研究了PKG激活对人结肠癌细胞SW 480中三种抑癌蛋白表达的影响。我们的研究结果表明，用细胞可渗透的cGMP衍生物或cGMP磷酸二酯酶抑制剂舒林砜（依昔舒林，aptosyn，以下称为依昔舒林）处理导致肿瘤抑制蛋白p21（CIP 1），p27（KIP 1）和组氨酸三联体蛋白1（HINTI）及其相应mRNA的表达增加。PKG I β的过表达也引起p21（CIP 1）、p27（KIP 1）和HINT 1蛋白的表达增加。p21（CIP 1）、p27（KIP 1）启动子均含有Sp1结合位点，并且在荧光素酶报告基因测定中它们被PKG激活。P21和P27启动子中的特异性Sp1位点足以介导PKG诱导的荧光素酶报告活性，表明Sp1和PKG之间存在相互作用。事实上，我们发现PKG可以磷酸化丝氨酸残基上的Sp1，这导致Sp1的转录激活。用siRNA敲低Sp1表达抑制了cGMP衍生物8-pCPT-cGMP诱导的SW 480细胞中p21（CIP 1）、p27（KIP 1）和HINT 1表达的增加。PKG激活对三种肿瘤抑制基因表达的这些新的影响可以解释，至少部分地，PKG激活的抗癌作用。它们还为进一步开发PKG活化剂用于预防和治疗癌症提供了理论基础。
The anticancer role of cyclic guanosine 3',5'-monophosphate (cGMP)-dependent protein kinase G (PKG) has become of considerable interest, but the underlying mechanisms are not fully established. In this study, we examined the effects of activation of PKG on the expression of three tumor suppressor proteins in human SW480 colon cancer cells. Our results revealed that treatment with cell permeable cGMP derivatives, or the cGMP phosphodiesterase inhibitor sulindac sulfone (exisulind, aptosyn, hereafter called exisulind) led to increased expression of the tumor suppressor proteins p21(CIP1), p27(KIP1), and Histidine triad protein 1 (HINTI), and their corresponding mRNAs. Overexpression of PKG I beta also caused increased expression of the p21(CIP1), p27(KIP1), and HINT1 proteins. Both the p21(CIP1), p27(KIP1) promoters contain Sp1 binding sites and they were activated by PKG in luciferase reporter assays. Specific Sp1 sites in the p21 and p27 promoters were sufficient to mediate PKG-induced luciferase reporter activity, suggesting an interaction between Sp1 and PKG. Indeed, we found that PKG can phosphorylate Sp1 on serine residue(s) and this resulted in transcriptional activation of Sp1. Knockdown of Sp1 expression with siRNA inhibited the increased expression of p21(CIP1), p27(KIP1), and HINT1 induced by the cGMP derivative 8-pCPT-cGMP in SW480 cells. These novel effects of PKG activation on the expression of three tumor suppressor genes may explain, at least in part, the anticancer effects of activation of PKG. They also provide a rationale for further developing activators of PKG for the prevention and treatment of cancer.