• BMB Reports
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• 제32권2호
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• pp.196-202
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• 1999

The existence of the Ras-independent signal transduction pathway of insulin leading to DNA synthesis was investigated in Rat-1 fibroblasts overexpressing human insulin receptor (HIRc-B) using the single-cell microinjection technique. Microinjection of a dominant-negative mutant $Ras^{N17}$ protein into quiescent HIRc-B cells inhibited the DNA synthesis stimulated by insulin. Microinjection of oncogenic H-$Ras^{V12}$ protein ($H-Ras^{V12}$) (0.1 mg/ml) induced DNA synthesis by 35%, whereas that of control-injected IgG was induced by 20%. When the marginal amount of oncogenic H-$Ras^{V12}$ protein was coinjected with a dominant-negative mutant of the H-Ras protein ($Ras^{N17}$), DNA synthesis was 35% and 74% in the absence and presence of insulin, respectively. This full recovery of DNA synthesis by insulin suggests the existence of the Ras-independent pathway. The same recovery was observed in the cells coinjected with either H-$Ras^{V12}$ plus H-$Ras^{N17}$ plus SH2 domain of the p85 subunit of PI3-kinase ($p85^{SH2-N}$) or H-$Ras^{V12}$ plus H-$Ras^{N17}$ plus interfering anti-Shc antibody. When co-injected with a dominant-negative H-$Ras^{N17}$, the DNA synthesis induced by the Ras-independent pathway was blocked. These results indicate that the Ras-independent pathway of insulin leading to DNA synthesis exists, bypassing the p85 of PI3-kinase and Shc protein, and requires Rac1 protein.

• Archives of Pharmacal Research
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• 제25권6호
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• pp.759-769
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• 2002

Mutated forms of ras are found in many human tumors and the rate of incidence is significantly higher in colon and pancreatic cancers. The protein product from the ras oncogene is a small G-protein, $p21^{ras}{\;}(Ras)$ that is known to playa key role in the signal transduction cascade and cell differentiation and proliferation. Mutated Ras is unable to regulate itself and remains constantly activated, leading to uncontrolled cell growth. The function of Ras in signal transduction requires its location near the growth factor receptor at the cell membrane. However, Ras does not have a transmembrane domain. Ras requires farnesylation to increase its hydrophobicity and subsequent plasma membrane association for its transforming activity. This key post-translational modification is catalyzed by the enzyme Ras farnesyltransferase (FTase), which transfers a farnesyl group from farnesylpyrophosphate to the C-terminal cysteine of the Ras protein. The requirement has focused attention on FTase as a target for therapeutic intervention. Selective inhibition of FTase will prevent Ras protein from association with the plasma membrane, leading to a disruption of oncogenic Ras function.

• 생명과학회지
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• 제28권9호
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• pp.1100-1117
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• 2018

Ras superfamily에 속하는 monomeric small GTPase는 현재까지 170여 종이 알려져 있으며 이들은 세포 신호전달에 있어서 분자 스위치(molecular switch)로 작용하고 있다. Ras GTPase는 guanosine diphosphate (GDP)와 결합하여 불활성화 되거나 혹은 guanosine triphosphate (GTP)와 결합하여 활성화되는 guanosine nucleotide 결합단백질로서 세포내의 수많은 생리작용을 조절하고 있다. 즉, 쉬고 있던 불활성화 상태의 Ras-GDP는 외부 신호에 반응하여 활성화 된 guanine nucleotide exchange factor (GEF)에 의하여 활성형인 Ras-GTP상태로 전환되어 그 하류로 신호를 전달하는 효과기로 작용하게 된다. 신호전달을 마친 Ras-GTP는 다시 불활성형인 Ras-GDP로 전환되어야 하는데 Ras 자체의 GTPase 활성이 미약하여 RasGTPase activating protein (RasGAP)의 도움을 받아야만 한다. 이와 같이 Ras GTPase는 GEF와 GAP의 활성으로 세포 안의 스위치를 켜고 끄게 된다. 현재까지 알려진 인간 암(cancer)의 30% 이상이 돌연변이를 포함하는 Ras switch의 비정상적인 작동에 기인한다는 점이 밝혀져 있으므로 Ras GTPase의 구조와 생리적 기능에 대한 최근의 연구결과들을 요약하였다. 나아가 GTPase activating protein으로서의 기능을 상실한 RasGAP분자의 돌연변이는 세포 안의 Ras 스위치를 계속 켜 두는 상태인 Ras-GTP 상태를 유발함으로서 종국에는 암의 발생을 촉발하게 된다. 이에, 본고에서는 최근에 와서 tumor suppressor로서 알려지면서 암의 치료 표적단백질로 떠오르게 된 RasGAP의 인체생리학적 기능을 고찰하였다. 인간 게놈 안에는 RASA1, NF1, GAP1 family 및 SynGAP family 등에 속하는 14종의 RasGAP 분자들이 존재하는데 이들 GAP분자들의 이상과 인간 질병의 연관성에 대한 최근의 연구결과들에 대해 고찰하였다.

• 통합자연과학논문집
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• 제16권2호
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• pp.47-51
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• 2023

Ras small GTPases are involved in regulating various cellular signaling pathways including cell migration, proliferation, and differentiation. Ras GTPase subfamily is comprised of 15 proteins; 11 Ras, 3 Rap, and one Rheb related protein. Some Ras proteins, such as RasC and RasG, have been identified for their major functions, but there are proteins whose functions have not been studied yet, such as RasU and RasX. Here, we investigated the roles of RasU in cell motility and development. RasU shows the highest homology with RasX. To investigate the functions of RasU, rasU null cells were used to observe the phenotype. Cells lacking RasU were larger and more spread than wild-type cells. These results indicate that RasU plays a negative role in cell spreading. In addition, we investigated the roles of RasU in cell motility and development of Dictyostelium cells and found that rasU null cells exhibited decreased random migration speed and delayed developmental process. These results suggest that RasU plays an important role in cell motility and development.

• 한국동물생명공학회지
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• 제35권1호
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• pp.12-20
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• 2020

Cell adhesion plays an important role in the differentiation of the morphogenesis and the trophectoderm epithelium of the blastocyst. In the porcine embryo, CDH1 mediated adhesion initiates at compaction before blastocyst formation, regulated post-translationally via protein kinase C and other signaling molecules. Here we focus on muscle RAS oncogene homolog (M-RAS), which is the closest relative to the RAS related proteins and shares most regulatory and effector interactions. To characterize the effects of M-RAS on embryo compaction, we used gain- and loss-of-function strategies in porcine embryos, in which M-RAS gene structure and protein sequence are conserved. We showed that knockdown of M-RAS in zygotes reduced embryo development abilities and CDH1 expression. Moreover, the phosphorylation of ERK was also decreased in M-RAS KD embryos. Overexpression of M-RAS allows M-RAS KD embryos to rescue the embryo compaction and blastocyst formation. Collectively, these results highlight novel conserved and multiple effects of M-RAS during porcine embryo development.

• BMB Reports
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• 제49권7호
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• pp.370-375
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• 2016

Ras oncoproteins are small molecular weight GTPases known for their involvement in oncogenesis, which operate in a complex signaling network with multiple effectors. Approximately 25% of human tumors possess mutations in a member of this family. The Raf1/MEK/Erk1/2 pathway is one of the most intensively studied signaling mechanisms. Different levels of regulation account for the inactivation of MAP kinases by MAPK phosphatases in a cell type- and stimuli-dependent manner. In the present study, using three inducible Ras-expressing NIH/3T3 cell lines, we demonstrated that MKP3 upregulation requires the activation of the Erk1/2 pathway, which correlates with the shutdown of this pathway. We also demonstrated, by applying pharmacological inhibitors and effector mutants of Ras, that induction of MKP3 at the protein level is positively regulated by the oncogenic Ras/Raf/MEK/Erk1/2 signaling pathway.

• Experimental and Molecular Medicine
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• 제50권11호
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• pp.12.1-12.12
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• 2018

Drugs targeting the epidermal growth factor receptor (EGFR), such as cetuximab and panitumumab, have been prescribed for metastatic colorectal cancer (CRC), but patients harboring KRAS mutations are insensitive to them and do not have an alternative drug to overcome the problem. The levels of ${\beta}$-catenin, EGFR, and RAS, especially mutant KRAS, are increased in CRC patient tissues due to mutations of adenomatous polyposis coli (APC), which occur in 90% of human CRCs. The increases in these proteins by APC loss synergistically promote tumorigenesis. Therefore, we tested KYA1797K, a recently identified small molecule that degrades both ${\beta}$-catenin and Ras via $GSK3{\beta}$ activation, and its capability to suppress the cetuximab resistance of KRAS-mutated CRC cells. KYA1797K suppressed the growth of tumor xenografts induced by CRC cells as well as tumor organoids derived from CRC patients having both APC and KRAS mutations. Lowering the levels of both ${\beta}$-catenin and RAS as well as EGFR via targeting the $Wnt/{\beta}$-catenin pathway is a therapeutic strategy for controlling CRC and other types of cancer with aberrantly activated the $Wnt/{\beta}$-catenin and EGFR-RAS pathways, including those with resistance to EGFR-targeting drugs attributed to KRAS mutations.

• BMB Reports
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• 제49권9호
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• pp.455-456
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• 2016

Mutations of APC and KRAS are frequently observed in human colorectal cancers (CRCs) and the Wnt/β-catenin and Ras pathways are consequently activated in a significant proportion of CRC patients. Mutations in these two genes are also known to synergistically induce progression of CRCs. Through a series of studies, we have demonstrated that inhibition of the Wnt/β-catenin signaling pathway negatively regulates Ras stability, therefore, Ras abundance is increased together with β-catenin in both mice and human CRCs harboring adenomatous polyposis coli (APC) mutations. In a recent study, we identified KY1220, a small molecule that simultaneously degrades β-catenin and Ras by inhibition of the Wnt/β-catenin pathway, and obtained its derivative KYA1797K, which has improved activity and solubility. We found that KYA1797K binds the RGS domain of axin and enhances the binding affinity of β-catenin or Ras with the β-catenin destruction complex components, leading to simultaneous destabilization of β-catenin and Ras via GSK3β activation. By using both in vitro and in vivo studies, we showed that KYA1797K suppressed the growth of CRCs harboring APC and KRAS mutations through destabilization of β-catenin and Ras. Therefore, our findings indicate that the simultaneous destabilization of β-catenin and Ras via targeting axin may serve as an effective strategy for inhibition of CRCs.

• BMB Reports
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• 제47권12호
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• pp.685-690
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• 2014

The Ras/Raf/MEK/Erk signaling pathway is important for regulation of cell growth, proliferation, differentiation, survival, and apoptosis in response to a variety of extracellular stimuli. Lack of Erk MAPK activation is observed in several cancer cells despite active activation of Ras. However, little is known about the modulation of Erk1/2 activity by active Ras. Here, we show that overexpression of active H-Ras (H-RasG12R) in NIH3T3 fibroblasts impaired FGF2-induced Erk1/2 phosphorylation, as compared to wild-type cells. Northern blot analysis revealed that prolonged expression of active Ras increased MAP kinase phosphatase 3 (MKP3) mRNA expression, a negative regulator of Erk MAPK. Inhibition of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway abrogated active Ras-induced up-regulation of MKP3 expression, leading to the rescue of Erk1/2 phosphorylation. Our results demonstrated that the Ras/Raf/MEK/Erk signaling cascade is negatively regulated by the PI3K/Aktdependent transcriptional activation of the MKP3 gene.

• Archives of Pharmacal Research
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• 제21권4호
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• pp.378-384
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• 1998

The processing pathway of G-proteins and Ras family proteins includes the isoprenylation of the cysteine residue, followed by proteolysis of three terminal residues and .alpha.-carboxyl methyl esterification of the cysteine residue. Farnesylcysteine methyltransferase (FCMT) activity is responsible for the methylation reaction which play a role in the membrane attachment of a variety of cellular proteins. Four kinds of Ras protein (c-Ha-ras, c-N-Ras, c-Ki-Ras, pan-Ras) expression were detected in adenocarcinoma of human tissue by immunohistochemical method, and hematoxylin and eosin staining. The level of Ras protein in human stomach tumor tissues was much higher than in normal and peritumoral regions of the same biopsy samples. The FCMT activities of each cellular fractions were high in mitochondrial fraction followed by microsomal fraction, whole homogenate and cytosolic fraction. The inhibitory effect on FCMT activity on stomach tumor tissue was determined after treatment with 0.25 $\mu\textrm{M}$ of S-adenosyl-$_L$-homocysteine. S-adenosyl-$_L$-homocysteine inhibited FCMT activity from 11.2% to 30.5%. These results suggested that FCMT might be involved in Ras proteins activity.