Insulin regulation of the Ras activation/inactivation cycle

AbstractSOS1 ablation causes specific defective phenotypes in MEFs including increased levels of intracellular ROS. We showed that the mitochondria-targeted antioxidant MitoTEMPO restores normal endogenous ROS levels, suggesting predominant involvement of mitochondria in generation of this defective SOS1-dependent phenotype. The absence of SOS1 caused specific alterations of mitochondrial shape, mass, and dynamics accompanied by higher percentage of dysfunctional mitochondria and lower rates of electron transport in comparison to WT or SOS2-KO counterparts. SOS1-deficient MEFs also exhibited specific alterations of respiratory complexes and their assembly into mitochondrial supercomplexes and consistently reduced rates of respiration, glycolysis, and ATP production, together with distinctive patterns of substrate preference for oxidative energy metabolism and dependence on glucose for survival. RASless cells showed defective respiratory/metabolic phenotypes reminiscent of those of SOS1-deficient MEFs, suggesting that the mitochondrial defects of these cells are mechanistically linked to the absence of SOS1-GEF activity on cellular RAS targets. Our observations provide a direct mechanistic link between SOS1 and control of cellular oxidative stress and suggest that SOS1-mediated RAS activation is required for correct mitochondrial dynamics and function.

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RasOncogene-Mediated Progressive Silencing of Extracellular Superoxide Dismutase in Tumorigenesis

BioMed Research International ◽

10.1155/2015/780409 ◽

2015 ◽

Vol 2015 ◽

pp. 1-13 ◽

Cited By ~ 9

Author(s):

Francesca Cammarota ◽

Gabriella de Vita ◽

Marco Salvatore ◽

Mikko O. Laukkanen

Keyword(s):

Superoxide Dismutase ◽

Cancer Cells ◽

Self Regulation ◽

Thyroid Cell ◽

Extracellular Superoxide Dismutase ◽

Mrna Synthesis ◽

Ras Activation ◽

Degree Of Differentiation ◽

In Cells

Extracellular superoxide dismutase (SOD3) is a secreted enzyme that uses superoxide anion as a substrate in a dismutase reaction that results in the formation of hydrogen peroxide. Both of these reactive oxygen species affect growth signaling in cells. Although SOD3 has growth-supporting characteristics, the expression ofSOD3is downregulated in epithelial cancer cells. In the current work, we studied the mechanisms regulatingSOD3expressionin vitrousing thyroid cell models representing different stages of thyroid cancer. We demonstrate that a low level of RAS activation increasesSOD3mRNA synthesis that then gradually decreases with increasing levels of RAS activation and the decreasing degree of differentiation of the cancer cells. Our data indicate thatSOD3regulation can be divided into two classes. The first class involves RAS–driven reversible regulation ofSOD3expression that can be mediated by the following mechanisms: RAS GTPase regulatory genes that are responsible forSOD3self-regulation; RAS-stimulated p38 MAPK activation; and RAS-activated increased expression of themir21microRNA, which inversely correlates withsod3mRNA expression. The second class involves permanent silencing ofSOD3mediated by epigenetic DNA methylation in cells that represent more advanced cancers. Therefore, the work suggests thatSOD3belongs to the group ofrasoncogene-silenced genes.

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Ras activation mediates WISP-1-induced increases in cell motility and matrix metalloproteinase expression in human osteosarcoma

Cellular Signalling ◽

10.1016/j.cellsig.2013.09.005 ◽

2013 ◽

Vol 25 (12) ◽

pp. 2812-2822 ◽

Cited By ~ 27

Author(s):

Chien-Lin Wu ◽

Hsiao-Chi Tsai ◽

Zhen-Wei Chen ◽

Chi-Ming Wu ◽

Te-Mao Li ◽

...

Keyword(s):

Matrix Metalloproteinase ◽

Cell Motility ◽

Human Osteosarcoma ◽

Ras Activation

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Gab1 and SHP-2 promote Ras/MAPK regulation of epidermal growth and differentiation

The Journal of Cell Biology ◽

10.1083/jcb.200205017 ◽

2002 ◽

Vol 159 (1) ◽

pp. 103-112 ◽

Cited By ~ 57

Author(s):

Ti Cai ◽

Keigo Nishida ◽

Toshio Hirano ◽

Paul A. Khavari

Keyword(s):

Epidermal Cell ◽

Mapk Signaling ◽

Dominant Negative ◽

Mapk Activity ◽

Ras Activation ◽

Proliferation And Differentiation ◽

Epidermal Proliferation ◽

Epidermal Growth ◽

Docking Protein

În epidermis, Ras can influence proliferation and differentiation; however, regulators of epidermal Ras function are not fully characterized, and Ras effects on growth and differentiation are controversial. EGF induced Ras activation in epidermal cells along with phosphorylation of the multisubstrate docking protein Gab1 and its binding to SHP-2. Expression of mutant Gab1Y627F deficient in SHP-2 binding or dominant-negative SHP-2C459S reduced basal levels of active Ras and downstream MAPK proteins and initiated differentiation. Differentiation triggered by both Gab1Y627F and SHP-2C459S could be blocked by coexpression of active Ras, consistent with Gab1 and SHP-2 action upstream of Ras in this process. To study the role of Gab1 and SHP-2 in tissue, we generated human epidermis overexpressing active Gab1 and SHP-2. Both proteins stimulated proliferation. In contrast, Gab1Y627F and SHP-2C459S inhibited epidermal proliferation and enhanced differentiation. Consistent with a role for Gab1 and SHP-2 in sustaining epidermal Ras/MAPK activity, Gab1−/− murine epidermis displayed lower levels of active Ras and MAPK with postnatal Gab1−/− epidermis, demonstrating the hypoplasia and enhanced differentiation seen previously with transgenic epidermal Ras blockade. These data provide support for a Ras role in promoting epidermal proliferation and opposing differentiation and indicate that Gab1 and SHP-2 promote the undifferentiated epidermal cell state by facilitating Ras/MAPK signaling.

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