IQGAP3 regulates cell proliferation through Ras/ERK signalling cascade

Laboratory of Biological Science, Graduate School of Frontier Biosciences/Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan.
Nature Cell Biology (Impact Factor: 19.68). 08/2008; 10(8):971-8. DOI: 10.1038/ncb1757
Source: PubMed


Proliferation of epithelial cells must be spatiotemporally regulated to maintain the organization of epithelial sheets. Here we show that the IQGAP family, comprising IQGAP1, 2 and 3, underlies lateral cell-cell contacts of epithelial cells. Of the three proteins, IQGAP3 is unique in that its expression is specifically confined to proliferating cells. Knockdown of IQGAP3 in cultured epithelial cells caused inhibition of proliferation and ERK activity. When exogenously expressed in quiescent cells, IQGAP3 was capable of inducing cell-cycle re-entry, which was completely inhibited by the MEK inhibitor U0126. Thus, IQGAP3 is necessary and sufficient for driving cell proliferation and ERK acts downstream of IQGAP3. Furthermore, IQGAP3 specifically interacted with the active, GTP-bound form of Ras, and in IQGAP3 knockdown cells, the activity of Ras, but not of other small GTPases, was inhibited. Thus, IQGAP3 regulates the promotion of cell proliferation through Ras-dependent ERK activation.

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    • "IQGAP3 is the latest addition to this family [24]. Data currently available suggest that it is involved in the proliferation of epithelial cells [34], [35], however its role in tumorigenesis remains to be determined. In the current study, we provide the first evidence that IQGAP3 promotes lung cancer growth and metastasis by enhancing EGFR-mediated ERK signaling. "
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    ABSTRACT: Proteins of the IQGAP family display complicated and often contradictory activities in tumorigenesis. IQGAP1 has well documented oncogenic potential and IQGAP2 has putative tumor-suppressive function. IQGAP3 is the latest addition to this family and its role in cancer development remains to be defined. Here we demonstrate IQGAP3 expression is markedly increased in lung cancer tissues at both mRNA and protein levels. Overexpression of IQGAP3 promoted tumor cell growth, and migration and invasion, whereas knockdown of IQGAP3 exhibited opposite effects. Moreover, suppression of IQGAP3 in a lung cancer cell line caused a reduction in the tumorigenicity of these cells in lung tissue after intravenous injection. Furthermore, we showed that IQGAP3 is able to interact with ERK1 and enhance its phosphorylation following treatment with EGF. These data suggest that IQGAP3 may contribute to the pathogenesis of lung cancer by modulating EGFR-ERK signaling.
    PLoS ONE 05/2014; 9(5):e97578. DOI:10.1371/journal.pone.0097578 · 3.23 Impact Factor
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    • "For instance, down-regulation of CNKSR2 in TDI chondrocytes may impair the crosstalk between MAPK and Ral pathways which is essential for proper receptor endocytosis, cytoskeleton remodeling and DNA synthesis [55]. Likewise, down-regulation of IQGAP3 and LSP1 as well as over-expression of NME1 may modify ERK1/2 activation upon PKC or Ras activation [56]–[58]. "
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    ABSTRACT: Endochondral ossification is the process by which the appendicular skeleton, facial bones, vertebrae and medial clavicles are formed and relies on the tight control of chondrocyte maturation. Fibroblast growth factor receptor (FGFR)3 plays a role in bone development and maintenance and belongs to a family of proteins which differ in their ligand affinities and tissue distribution. Activating mutations of the FGFR3 gene lead to craniosynostosis and multiple types of skeletal dysplasia with varying degrees of severity: thanatophoric dysplasia (TD), achondroplasia and hypochondroplasia. Despite progress in the characterization of FGFR3-mediated regulation of cartilage development, many aspects remain unclear. The aim and the novelty of our study was to examine whole gene expression differences occurring in primary human chondrocytes isolated from normal cartilage or pathological cartilage from TD-affected fetuses, using Affymetrix technology. The phenotype of the primary cells was confirmed by the high expression of chondrocytic markers. Altered expression of genes associated with many cellular processes was observed, including cell growth and proliferation, cell cycle, cell adhesion, cell motility, metabolic pathways, signal transduction, cell cycle process and cell signaling. Most of the cell cycle process genes were down-regulated and consisted of genes involved in cell cycle progression, DNA biosynthesis, spindle dynamics and cytokinesis. About eight percent of all modulated genes were found to impact extracellular matrix (ECM) structure and turnover, especially glycosaminoglycan (GAG) and proteoglycan biosynthesis and sulfation. Altogether, the gene expression analyses provide new insight into the consequences of FGFR3 mutations in cell cycle regulation, onset of pre-hypertrophic differentiation and concomitant metabolism changes. Moreover, impaired motility and ECM properties may also provide clues about growth plate disorganization. These results also suggest that many signaling pathways may be directly or indirectly altered by FGFR3 and confirm the crucial role of FGFR3 in the control of growth plate development.
    PLoS ONE 10/2009; 4(10):e7633. DOI:10.1371/journal.pone.0007633 · 3.23 Impact Factor

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