Wadhwa Renu, Yaguchi Tomoko, Hasan Md Kamrul, Taira Kazunari, Kaul Sunil C
National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan.
Biochem Biophys Res Commun. 2003 Mar 21;302(4):735-42. doi: 10.1016/s0006-291x(03)00226-2.
Mortalin (mot-2/GRP75/PBP74/mthsp70) is a member of the hsp70 family of proteins and is differentially distributed in normal and immortal cells. It was shown to be involved in pathways to cell senescence and immortalization. To elucidate its functional aspects, a yeast interactive screen for mortalin (mot-2) binding proteins was performed. Mevalonate pyrophosphate decarboxylase (MPD) was identified as one of the mortalin binding partners. The interactions were confirmed in mammalian cells by two-hybrid assay and in vivo coimmunoprecipitation. MPD is known to furnish prenyl groups required for prenylation, protein modification that is essential for the activity of many proteins including p21(Ras) (Ras). We have examined the effect of MPD-mot-2 interactions on the level and activity of p21(Ras) and its downstream effectors, p44 and p42 MAP kinases (ERK1/ERK2), in Ras-Raf pathway. An overexpression of mot-2 resulted in reduced level of Ras and phosphorylated ERK2. These were rescued by co-expression of MPD from an exogenous promoter demonstrating a functional link between mot-2, MPD, and Ras. Ras and its oncogenic forms act as key players in controlling proliferation of normal and cancerous cells. Assigning mot-2 upstream of p21(Ras) offers an important mechanism for influence over cell proliferation.
mortalin（mot-2/GRP75/PBP74/mthsp70）是热休克蛋白70（hsp70）家族的一员，在正常细胞和永生化细胞中分布不同。研究表明，它参与细胞衰老和永生化途径。为阐明其功能，我们进行了酵母双杂交筛选mortalin（mot-2）结合蛋白的实验。甲羟戊酸焦磷酸脱羧酶（MPD）被鉴定为mortalin的结合伴侣之一。通过双杂交实验和体内免疫共沉淀在哺乳动物细胞中证实了这种相互作用。已知MPD提供异戊二烯化所需的异戊二烯基团，而异戊二烯化是包括p21（Ras）（Ras）在内的许多蛋白质活性所必需的蛋白质修饰。我们研究了MPD与mot-2相互作用对Ras-Raf途径中p21（Ras）及其下游效应分子p44和p42丝裂原活化蛋白激酶（ERK-1/ERK-2）水平和活性的影响。mot-2的过表达导致Ras和磷酸化ERK-2水平降低。通过从外源启动子共表达MPD可挽救这种降低，这表明mot-2、MPD和Ras之间存在功能联系。Ras及其致癌形式在控制正常细胞和癌细胞增殖中起关键作用。确定mot-2在p21（Ras）上游为影响细胞增殖提供了一个重要机制。
