The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Ichiro Tatsuno - One of the best experts on this subject based on the ideXlab platform.
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fatty acid desaturase 2 is up regulated by the treatment with statin through Geranylgeranyl Pyrophosphate dependent rho kinase pathway in hepg2 cells
Scientific Reports, 2019Co-Authors: Shou Tanaka, Tomoaki Tanaka, Noriko Ishihara, Sawako Suzuki, Yasuhiro Watanabe, Daiji Nagayama, Atsuhito Saiki, Takashi Yamaguchi, Masahiro Ohira, Ichiro TatsunoAbstract:Statins have been reported to increase the plasma concentration of arachidonic acid (AA), an omega-6 long chain polyunsaturated fatty acid (LCPUFA) in several clinical studies indicating that statins affect the endogenous synthesis of LCUFAs. In the present study, we investigated the roles of the intrinsic mevalonate cascade and Rho-dependent pathway in LCPUFA synthesis, especially focusing on fatty acid desaturases (Fads) 2, using the human hepatocellular carcinoma cell line HepG2. Cell number and the activity of caspase-3 and 7 (caspase-3/7) was measured using a commercial kit. Gene expression was analyzed by quantitative real-time PCR. Protein expression was detected by Western blot analysis. Atorvastatin decreased cell viability and increased caspase-3/7 activity in a dose-dependent manner. At lower concentrations, atorvastatin stimulated both mRNA and protein expression of Fads2, and increased mRNA expression of FADS1 and ELVOL5. Both mevalonate and Geranylgeranyl-Pyrophosphate (GGPP), but not cholesterol, fully reversed atorvastatin-induced upregulation of Fads2, and mevalonate-effected reversal was inhibited by treatment with the Rho-associated protein kinase inhibitor Y-27632. These data clearly demonstrated that in human HepG2 cells, statins affect the endogenous synthesis of LCPUFAs by regulation of not only Fads2, but also Fads1 and Elovl5, through the GGPP-dependent Rho kinase pathway.
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atorvastatin increases fatty acid desaturases fadss and elongation of very long chain fatty acids elovls through Geranylgeranyl Pyrophosphate ggpp dependent rho kinase pathway in hepg2 cells
Diabetes, 2018Co-Authors: Ichiro Tatsuno, Shou Tanaka, Noriko IshiharaAbstract:Background: The plasma concentration of arachidonic acid, one of the omega-6 long-chain polyunsaturated fatty acids (LCPUFAs), was increased by the treatment of statin in several clinical studies indicating that statin affects the endogenous synthesis of LCPUFAs, which is regulated by the action of the fatty acid desaturases (FADSs) and elongation of very long-chain fatty acids (ELOVLs). Aims: We investigated the roles of the intrinsic mevalonate cascade and rho-dependent pathway in the statin-induced regulation of these desaturases and elongases using human hepatocellular carcinoma cell line HepG2 cells. Methods: Cell viability was assessed by measuring mitochondrial activity of WST-8, and the activity of caspase-3 and -7 (caspase-3/7) was measured. Gene expression was analyzed by quantitative real-time PCR. Protein expressions were detected by Western blot analysis. Results: Although atorvastatin decreased the cell viability with increasing activity of caspase-3/7 in a dose-dependent manner, both mRNA and protein expression of FADS2 were stimulated by atorvastatin at lower dose of 12.5 and 25 uM, where mRNA expression of FADS1 and Elovl5 also increased. Both mevalonate and Geranylgeranyl-Pyrophosphate (GGPP), not cholesterol, fully restored the atorvastatin-induced inhibition of cell viability, and the atorvastatin-induced upregulation of mRNA and protein of FADS2. The Rho-associated protein kinase (ROCK) inhibitor Y-27632 inhibits the restoration of mevalonate and GGPP. Both EPA and DHA, but not AA, significantly suppressed the atorvastatin-induced upregulation of gene expression of FADS1, FADS2 and Elovl5. Conclusions: These data demonstrated that statin may affect the endogenous synthesis of LCPUFAs by the regulation of these desaturases and elongases through GGPP-dependent rho kinase pathway in HepG2 cells. Disclosure I. Tatsuno: None. S. Tanaka: None. N. Ishihara: None.
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atorvastatin increases fads1 fads2 and elovl5 gene expression via the Geranylgeranyl Pyrophosphate dependent rho kinase pathway in 3t3 l1 cells
Molecular Medicine Reports, 2017Co-Authors: Noriko Ishihara, Tomoaki Tanaka, Sawako Suzuki, Shou Tanaka, Yasuhiro Watanabe, Daiji Nagayama, Atsuhito Saiki, Ichiro TatsunoAbstract:Numerous clinical studies have reported that statins increase the plasma concentration of arachidonic acid, which is an ω-6 long-chain polyunsaturated fatty acid (LCPUFA), and decrease the concentrations of eicosapentaenoic acid and docosahexaenoic acid, which are ω‑3 LCPUFAs. These findings indicate that statins may affect the endogenous synthesis of LCPUFAs, which is regulated by fatty acid desaturases (FADSs) and elongation of very long‑chain fatty acids proteins (ELOVLs). The present study aimed to investigate the roles of the intrinsic mevalonate cascade and Rho‑dependent pathway in statin‑induced regulation of these desaturases and elongases, as well as cell viability using mouse 3T3‑L1 cells. mRNA expression was analyzed by quantitative polymerase chain reaction. Treatment with atorvastatin decreased cell viability and increased the mRNA expression levels of Fads1, Fads2 and ELOVL fatty acid elongase 5 (Elovl5) in a dose‑dependent manner. Mevalonate and Geranylgeranyl Pyrophosphate (GGPP), but not cholesterol, fully reversed the atorvastatin‑induced downregulation of cell viability and upregulation of gene expression; however, mevalonate itself did not affect cell viability and gene expression. The Rho‑associated protein kinase inhibitor Y‑27632 inhibited the mevalonate‑ and GGPP‑mediated reversal of atorvastatin‑induced upregulation of Fads1, Fads2 and Elovl5. These findings indicated that statins may affect the endogenous synthesis of LCPUFAs by regulating Fads1, Fads2 and Elovl5 gene expression via the GGPP‑dependent Rho kinase pathway in mouse 3T3-L1 cells.
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regulation of Geranylgeranyl Pyrophosphate synthase in the proliferation of rat frtl 5 cells involvement of both camp pka and pi3 akt pathways
Biochemical and Biophysical Research Communications, 2004Co-Authors: Masami Fuse, Tomohiko Yoshida, Takahisa Shibata, Tomoaki Tanaka, Tatsuji Yasuda, Yasushi Saito, Norihiko Misawa, Yoshihiko Noguchi, Leonard D Kohn, Ichiro TatsunoAbstract:Abstract 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.
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Geranylgeranylated Rho Small GTPase(s) Are Essential for the Degradation of p27Kip1 and Facilitate the Progression from G1 to S Phase in Growth-stimulated Rat FRTL-5 Cells
Journal of Biological Chemistry, 1997Co-Authors: Aizan Hirai, Tatsuji Yasuda, Ichiro Tatsuno, Susumu Nakamura, Yoshihiko Noguchi, Masatoshi Kitagawa, Toru Oeda, Kazuo Tahara, Takashi Terano, Shuh NarumiyaAbstract:Abstract Cyclin-dependent kinase (Cdk) enzymes are activated for entry into the S phase of the cell cycle. Elimination of Cdk inhibitor protein p27Kip1 during the G1 to S phase is required for the activation process. An inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase prevents its elimination and leads to G1 arrest. Mevalonate and its metabolite, Geranylgeranyl Pyrophosphate, but not farnesyl Pyrophosphate, restore the inhibitory effect of pravastatin on the degradation of p27 and allow Cdk2 activation. By the addition of Geranylgeranyl Pyrophosphate, Rho small GTPase(s) are Geranylgeranylated and translocated to membranes during G1/S progression. The restoring effect of Geranylgeranyl Pyrophosphate is abolished with botulinum C3 exoenzyme, which specifically inactivates Rho. These results indicate (i) among mevalonate metabolites, Geranylgeranyl Pyrophosphate is absolutely required for the elimination of p27 followed by Cdk2 activation; (ii) Geranylgeranylated Rho small GTPase(s) promote the degradation of p27 during G1/S transition in FRTL-5 cells.
Miguel C Seabra - One of the best experts on this subject based on the ideXlab platform.
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rab Geranylgeranylation occurs preferentially via the pre formed rep rggt complex and is regulated by Geranylgeranyl Pyrophosphate
Biochemical Journal, 2008Co-Authors: Rudi Baron, Miguel C SeabraAbstract:Prenylation (or Geranylgeranylation) of Rab GTPases is catalysed by RGGT (Rab Geranylgeranyl transferase) and requires REP (Rab escort protein). In the classical pathway, REP associates first with unprenylated Rab, which is then prenylated by RGGT. In the alternative pathway, REP associates first with RGGT; this complex then binds and prenylates Rab proteins. In the present paper we show that REP mutants defective in RGGT binding (REP1 F282L and REP1 F282L/V290F) are unable to compete with wild-type REP in the prenylation reaction in vitro . When over-expressed in cells, REP wild-type and mutants are unable to form stable cytosolic complexes with endogenous unprenylated Rabs. These results suggest that the alternative pathway may predominate in vivo . We also extend previous suggestions that GGPP (Geranylgeranyl Pyrophosphate) acts as an allosteric regulator of the prenylation reaction. We observed that REP–RGGT complexes are formed in vivo and are unstable in the absence of intracellular GGPP. RGGT increases the ability of REP to extract endogenous prenylated Rabs from membranes in vitro by stabilizing a soluble REP–RGGT–Rab-GG (Geranylgeranylated Rab) complex. This effect is regulated by GGPP, which promotes the dissociation of RGGT and REP–Rab-GG to allow delivery of prenylated Rabs to membranes.
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Rab Geranylgeranylation occurs preferentially via the pre-formed REP–RGGT complex and is regulated by Geranylgeranyl Pyrophosphate
Biochemical Journal, 2008Co-Authors: Rudi A. Baron, Miguel C SeabraAbstract:Prenylation (or Geranylgeranylation) of Rab GTPases is catalysed by RGGT (Rab Geranylgeranyl transferase) and requires REP (Rab escort protein). In the classical pathway, REP associates first with unprenylated Rab, which is then prenylated by RGGT. In the alternative pathway, REP associates first with RGGT; this complex then binds and prenylates Rab proteins. In the present paper we show that REP mutants defective in RGGT binding (REP1 F282L and REP1 F282L/V290F) are unable to compete with wild-type REP in the prenylation reaction in vitro . When over-expressed in cells, REP wild-type and mutants are unable to form stable cytosolic complexes with endogenous unprenylated Rabs. These results suggest that the alternative pathway may predominate in vivo . We also extend previous suggestions that GGPP (Geranylgeranyl Pyrophosphate) acts as an allosteric regulator of the prenylation reaction. We observed that REP–RGGT complexes are formed in vivo and are unstable in the absence of intracellular GGPP. RGGT increases the ability of REP to extract endogenous prenylated Rabs from membranes in vitro by stabilizing a soluble REP–RGGT–Rab-GG (Geranylgeranylated Rab) complex. This effect is regulated by GGPP, which promotes the dissociation of RGGT and REP–Rab-GG to allow delivery of prenylated Rabs to membranes.
Marcel Kuntz - One of the best experts on this subject based on the ideXlab platform.
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structure of a functional Geranylgeranyl Pyrophosphate synthase gene from capsicum annuum
Plant Molecular Biology, 1995Co-Authors: Alfredo Badillo, Bilal Camara, Johannes Steppuhn, Jean Deruere, Marcel KuntzAbstract:A Geranylgeranyl Pyrophosphate synthase (GGPPS) gene from Capsicum annuum (bell pepper) was cloned. The nucleotide sequence shows that this gene, like the capsanthin/capsorubin gene but unlike the phytoene synthase gene from C. annuum, is not interrupted by an intron. Southern blot analysis of C. annuum genomic DNA suggests the presence of a single gene highly similar to the cDNA and also of additional related sequences. The present data suggest that this cloned gene is functional.
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identification of a cdna for the plastid located Geranylgeranyl Pyrophosphate synthase from capsicum annuum correlative increase in enzyme activity and transcript level during fruit ripening
Plant Journal, 1992Co-Authors: Marcel Kuntz, Susanne Romer, C Suire, Philippe Hugueney, Jacqueshenry Weil, Rudy Schantz, Bilal CamaraAbstract:Geranylgeranyl Pyrophosphate synthase is a key enzyme in plant terpenoid biosynthesis. Using specific antibodies, a cDNA encoding Geranylgeranyl Pyrophosphate synthase has been isolated from bell pepper (Capsicum annuum) ripening fruit. The cloned cDNA codes for a high molecular weight precursor of 369 amino acids which contains a transit peptide of approximately 60 amino acids. In-situ immunolocalization experiments have demonstrated that Geranylgeranyl Pyrophosphate synthase is located exclusively in the plastids. Expression of the cloned cDNA in E. cob has unambiguously demonstrated that the encoded polypeptide catalyzes the synthesis of Geranylgeranyl Pyrophosphate by the addition of isopentenyl Pyrophosphate to an allylic Pyrophosphate. Peptide sequence comparisons revealed significant similarity between the sequences of the C. annuum Geranylgeranyl Pyrophosphate synthase and those deduced from carotenoid biosynthesis (crtE) genes from photosynthetic and non-photosynthetic bacteria. In addition, four highly conserved regions, which are found in various prenyltransferases, were identified. Furthermore, evidence is provided suggesting that conserved and exposed carboxylates are directly involved in the catalytic mechanism. Finally, the expression of the Geranylgeranyl Pyrophosphate synthase gene is demonstrated to be strongly induced during the chloroplast to chromoplast transition which occurs in ripening fruits, and is correlated with an increase in enzyme activity.
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Identification of a cDNA for the plastid‐located Geranylgeranyl Pyrophosphate synthase from Capsicum annuum: correlative increase in enzyme activity and transcript level during fruit ripening
Plant Journal, 1992Co-Authors: Marcel Kuntz, Susanne Romer, C Suire, Philippe Hugueney, Jacqueshenry Weil, Rudy Schantz, Bilal CamaraAbstract:Geranylgeranyl Pyrophosphate synthase is a key enzyme in plant terpenoid biosynthesis. Using specific antibodies, a cDNA encoding Geranylgeranyl Pyrophosphate synthase has been isolated from bell pepper (Capsicum annuum) ripening fruit. The cloned cDNA codes for a high molecular weight precursor of 369 amino acids which contains a transit peptide of approximately 60 amino acids. In-situ immunolocalization experiments have demonstrated that Geranylgeranyl Pyrophosphate synthase is located exclusively in the plastids. Expression of the cloned cDNA in E. cob has unambiguously demonstrated that the encoded polypeptide catalyzes the synthesis of Geranylgeranyl Pyrophosphate by the addition of isopentenyl Pyrophosphate to an allylic Pyrophosphate. Peptide sequence comparisons revealed significant similarity between the sequences of the C. annuum Geranylgeranyl Pyrophosphate synthase and those deduced from carotenoid biosynthesis (crtE) genes from photosynthetic and non-photosynthetic bacteria. In addition, four highly conserved regions, which are found in various prenyltransferases, were identified. Furthermore, evidence is provided suggesting that conserved and exposed carboxylates are directly involved in the catalytic mechanism. Finally, the expression of the Geranylgeranyl Pyrophosphate synthase gene is demonstrated to be strongly induced during the chloroplast to chromoplast transition which occurs in ripening fruits, and is correlated with an increase in enzyme activity.
Rudi Baron - One of the best experts on this subject based on the ideXlab platform.
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rab Geranylgeranylation occurs preferentially via the pre formed rep rggt complex and is regulated by Geranylgeranyl Pyrophosphate
Biochemical Journal, 2008Co-Authors: Rudi Baron, Miguel C SeabraAbstract:Prenylation (or Geranylgeranylation) of Rab GTPases is catalysed by RGGT (Rab Geranylgeranyl transferase) and requires REP (Rab escort protein). In the classical pathway, REP associates first with unprenylated Rab, which is then prenylated by RGGT. In the alternative pathway, REP associates first with RGGT; this complex then binds and prenylates Rab proteins. In the present paper we show that REP mutants defective in RGGT binding (REP1 F282L and REP1 F282L/V290F) are unable to compete with wild-type REP in the prenylation reaction in vitro . When over-expressed in cells, REP wild-type and mutants are unable to form stable cytosolic complexes with endogenous unprenylated Rabs. These results suggest that the alternative pathway may predominate in vivo . We also extend previous suggestions that GGPP (Geranylgeranyl Pyrophosphate) acts as an allosteric regulator of the prenylation reaction. We observed that REP–RGGT complexes are formed in vivo and are unstable in the absence of intracellular GGPP. RGGT increases the ability of REP to extract endogenous prenylated Rabs from membranes in vitro by stabilizing a soluble REP–RGGT–Rab-GG (Geranylgeranylated Rab) complex. This effect is regulated by GGPP, which promotes the dissociation of RGGT and REP–Rab-GG to allow delivery of prenylated Rabs to membranes.
Tomoaki Tanaka - One of the best experts on this subject based on the ideXlab platform.
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fatty acid desaturase 2 is up regulated by the treatment with statin through Geranylgeranyl Pyrophosphate dependent rho kinase pathway in hepg2 cells
Scientific Reports, 2019Co-Authors: Shou Tanaka, Tomoaki Tanaka, Noriko Ishihara, Sawako Suzuki, Yasuhiro Watanabe, Daiji Nagayama, Atsuhito Saiki, Takashi Yamaguchi, Masahiro Ohira, Ichiro TatsunoAbstract:Statins have been reported to increase the plasma concentration of arachidonic acid (AA), an omega-6 long chain polyunsaturated fatty acid (LCPUFA) in several clinical studies indicating that statins affect the endogenous synthesis of LCUFAs. In the present study, we investigated the roles of the intrinsic mevalonate cascade and Rho-dependent pathway in LCPUFA synthesis, especially focusing on fatty acid desaturases (Fads) 2, using the human hepatocellular carcinoma cell line HepG2. Cell number and the activity of caspase-3 and 7 (caspase-3/7) was measured using a commercial kit. Gene expression was analyzed by quantitative real-time PCR. Protein expression was detected by Western blot analysis. Atorvastatin decreased cell viability and increased caspase-3/7 activity in a dose-dependent manner. At lower concentrations, atorvastatin stimulated both mRNA and protein expression of Fads2, and increased mRNA expression of FADS1 and ELVOL5. Both mevalonate and Geranylgeranyl-Pyrophosphate (GGPP), but not cholesterol, fully reversed atorvastatin-induced upregulation of Fads2, and mevalonate-effected reversal was inhibited by treatment with the Rho-associated protein kinase inhibitor Y-27632. These data clearly demonstrated that in human HepG2 cells, statins affect the endogenous synthesis of LCPUFAs by regulation of not only Fads2, but also Fads1 and Elovl5, through the GGPP-dependent Rho kinase pathway.
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atorvastatin increases fads1 fads2 and elovl5 gene expression via the Geranylgeranyl Pyrophosphate dependent rho kinase pathway in 3t3 l1 cells
Molecular Medicine Reports, 2017Co-Authors: Noriko Ishihara, Tomoaki Tanaka, Sawako Suzuki, Shou Tanaka, Yasuhiro Watanabe, Daiji Nagayama, Atsuhito Saiki, Ichiro TatsunoAbstract:Numerous clinical studies have reported that statins increase the plasma concentration of arachidonic acid, which is an ω-6 long-chain polyunsaturated fatty acid (LCPUFA), and decrease the concentrations of eicosapentaenoic acid and docosahexaenoic acid, which are ω‑3 LCPUFAs. These findings indicate that statins may affect the endogenous synthesis of LCPUFAs, which is regulated by fatty acid desaturases (FADSs) and elongation of very long‑chain fatty acids proteins (ELOVLs). The present study aimed to investigate the roles of the intrinsic mevalonate cascade and Rho‑dependent pathway in statin‑induced regulation of these desaturases and elongases, as well as cell viability using mouse 3T3‑L1 cells. mRNA expression was analyzed by quantitative polymerase chain reaction. Treatment with atorvastatin decreased cell viability and increased the mRNA expression levels of Fads1, Fads2 and ELOVL fatty acid elongase 5 (Elovl5) in a dose‑dependent manner. Mevalonate and Geranylgeranyl Pyrophosphate (GGPP), but not cholesterol, fully reversed the atorvastatin‑induced downregulation of cell viability and upregulation of gene expression; however, mevalonate itself did not affect cell viability and gene expression. The Rho‑associated protein kinase inhibitor Y‑27632 inhibited the mevalonate‑ and GGPP‑mediated reversal of atorvastatin‑induced upregulation of Fads1, Fads2 and Elovl5. These findings indicated that statins may affect the endogenous synthesis of LCPUFAs by regulating Fads1, Fads2 and Elovl5 gene expression via the GGPP‑dependent Rho kinase pathway in mouse 3T3-L1 cells.
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Geranylgeranyl Pyrophosphate ggpp synthase is down regulated during differentiation of osteoblastic cell line mc3t3 e1
FEBS Letters, 2006Co-Authors: Tomohiko Yoshida, Mie Asanuma, Laura Grossmann, Masami Fuse, Takahisa Shibata, Taeko Yonekawa, Tomoaki Tanaka, Koichi Ueno, Tatsuji Yasuda, Yasushi SaitoAbstract:Isoprenylation of Geranylgeranyl-Pyrophosphate (GGPP) is critical for activation of small GTPases. We examined the roles of GGPP synthase (GGPPS) during the differentiation induced by the cell-to-cell contact in osteoblastic cell line MC3T3-E1 cells. We found that (1) both mRNA and protein expression of GGPPS was reduced with decrement of its activity during the differentiation, (2) GGOH, which is converted to GGPP in the cells, inhibited differentiation. These results suggest that the decrement of GGPP is critical for the cell-to-cell contact-induced differentiation, in which the down-regulation of GGPPS might be involved.
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regulation of Geranylgeranyl Pyrophosphate synthase in the proliferation of rat frtl 5 cells involvement of both camp pka and pi3 akt pathways
Biochemical and Biophysical Research Communications, 2004Co-Authors: Masami Fuse, Tomohiko Yoshida, Takahisa Shibata, Tomoaki Tanaka, Tatsuji Yasuda, Yasushi Saito, Norihiko Misawa, Yoshihiko Noguchi, Leonard D Kohn, Ichiro TatsunoAbstract:Abstract 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.