Fuse Masami, Tanaka Tomoaki, Shibata Takahisa, Yoshida Tomohiko, Noguchi Yoshihiko, Misawa Norihiko, Yasuda Tatsuji, Saito Yasushi, Kohn Leonard D, Tatsuno Ichiro
Department of Clinical Cell Biology, Graduate School of Medicine, Chiba University, Chiba, Japan.
Biochem Biophys Res Commun. 2004 Mar 19;315(4):1147-53. doi: 10.1016/j.bbrc.2004.02.008.
We have reported that geranylgeranyl pyrophosphate (GGPP), one of the isoprenoids in the mevalonate pathway, plays an essential role for cell growth through the geranylgeranylation of Rho small GTPases, which control the degradation of P27Kip1 at G1/S transition in rat thyroid FRTL-5 cells. Since GGPP is synthesized from isopentenyl pyrophosphate (IPP) and farnesyl pyrophosphate (FPP) by GGPP synthase, we analyzed the regulatory roles of GGPP synthase in the proliferation of FRTL-5 cells stimulated by thyrotropin and insulin in the presence of 5% calf serum (TSH+Ins). We found that: (1) GGPP synthase was activated at G1/S transition with increasing mRNA accumulation followed by protein expression, (2) pravastatin, an inhibitor of HMG-CoA reductase, did not suppress the increasing activity of GGPP synthase with its protein expression although it inhibits proliferation in growth-stimulated FRTL-5 cells, (3) forskolin stimulated proliferation with activation of GGPP synthase in FRTL-5 cells, and (4) LY294002, an inhibitor of phosphatidylinositol 3-kinase, inhibited proliferation with the decreasing activity of GGPP synthase in growth-stimulated FRTL-5 cells. These data indicated that growth stimulation by TSH+Ins increased the activity of GGPP synthase with its increasing protein expression from G1/S transition, in which both cAMP-PKA and PI3-kinase pathways are involved in the proliferation of FRTL-5 cells.
我们曾报道，香叶基香叶基焦磷酸（GGPP）是甲羟戊酸途径中的类异戊二烯之一，通过Rho小GTP酶的香叶基香叶基化作用对细胞生长起着至关重要的作用，Rho小GTP酶在大鼠甲状腺FRTL-5细胞的G1/S期转换过程中控制P27Kip1的降解。由于GGPP是由香叶基香叶基焦磷酸合酶从异戊烯基焦磷酸（IPP）和法尼基焦磷酸（FPP）合成而来，我们分析了香叶基香叶基焦磷酸合酶在5%小牛血清（TSH+Ins）存在的情况下，对促甲状腺激素和胰岛素刺激的FRTL-5细胞增殖的调节作用。我们发现：（1）GGPP合酶在G1/S期转换时被激活，mRNA积累增加，随后蛋白质表达增加；（2）HMG-CoA还原酶抑制剂普伐他汀虽然抑制生长刺激的FRTL-5细胞的增殖，但不抑制GGPP合酶活性及其蛋白质表达的增加；（3）福斯可林通过激活FRTL-5细胞中的GGPP合酶来刺激增殖；（4）磷脂酰肌醇3-激酶抑制剂LY294002通过降低生长刺激的FRTL-5细胞中GGPP合酶的活性来抑制增殖。这些数据表明，TSH+Ins的生长刺激通过从G1/S期转换增加蛋白质表达，从而增加了GGPP合酶的活性，其中cAMP-PKA和PI3-激酶途径均参与了FRTL-5细胞的增殖。
