HIP/PAP, a C-type lectin overexpressed in hepatocellular carcinoma, binds the RIIα regulatory subunit of cAMP-dependent protein kinase and alters the cAMP-dependent protein kinase signalling
HIP/PAP, a C-type lectin overexpressed in hepatocellular carcinoma, binds the RIIα regulatory subunit of cAMP-dependent protein kinase and alters the cAMP-dependent protein kinase signalling
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DOI：
10.1111/j.1432-1033.2004.04302.x
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发表时间：
2004-10-01
期刊：
影响因子：
--
通讯作者：
Brechot, C
中科院分区：
文献类型：
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作者：
Demaugre, F;Philippe, Y;Brechot, C
HIP/PAP 是一种在肝细胞癌 (HCC) 中过度表达的 C 型凝集素。这种蛋白质具有多效性生物活性，但人们对 HIP/PAP 在肝脏中的功能知之甚少。因此，在本研究中，我们通过筛选 HCC cDNA 表达文库来寻找与 HIP/PAP 相互作用的蛋白质。我们已经确定 cAMP 依赖性蛋白激酶 (PKA) 的 RIIalpha 调节亚基是 HIP/PAP 的伙伴。 HIP/PAP 和 RIIalpha 在 HIP/PAP 表达细胞中进行免疫共沉淀。这些蛋白质之间相互作用的生物学相关性是通过使用分级分离方法证明它们位于同一亚细胞区室中而建立的。事实上，虽然 HIP/PAP 是通过高尔基体分泌的蛋白质，但我们发现一部分 HIP/PAP 逃逸出分泌装置并在细胞质中回收。 HIP/PAP 表达细胞的基础 PKA 活性增加，表明 HIP/PAP 可能改变 PKA 信号传导。事实上，我们发现，使用胸苷激酶-荧光素酶报告质粒（其中在胸苷激酶启动子上游插入了 cAMP 响应元件），HIP/PAP 表达细胞中的荧光素酶活性得到增强。因此，我们的研究结果提出了 HIP/PAP 凝集素生物活性的新机制。
HIP/PAP is a C-type lectin overexpressed in hepatocellular carcinoma (HCC). Pleiotropic biological activities have been ascribed to this protein, but little is known about the function of HIP/PAP in the liver. In this study, therefore, we searched for proteins interacting with HIP/PAP by screening a HCC cDNA expression library. We have identified the RIIalpha regulatory subunit of cAMP-dependent protein kinase (PKA) as a partner of HIP/PAP. HIP/PAP and RIIalpha were coimmunoprecipitated in HIP/PAP expressing cells. The biological relevance of the interaction between these proteins was established by demonstrating, using fractionation methods, that they are located in a same subcellular compartment. Indeed, though HIP/PAP is a protein secreted via the Golgi apparatus we showed that a fraction of HIP/PAP escaped the secretory apparatus and was recovered in the cytosol. Basal PKA activity was increased in HIP/PAP expressing cells, suggesting that HIP/PAP may alter PKA signalling. Indeed, we showed, using a thymidine kinase-luciferase reporter plasmid in which a cAMP responsive element was inserted upstream of the thymidine kinase promoter, that luciferase activity was enhanced in HIP/PAP expressing cells. Thus our findings suggest a novel mechanism for the biological activity of the HIP/PAP lectin.