Gα12/13 Basally Regulates p53 through Mdm4 Expression

Molecular and Cellular Biology

et al. 2007

Self Cite

G␣ 12 and G␣ 13 function as molecular regulators responding to extracellular stimuli. NF-E2-related factor 2 (Nrf2) is involved in a protective adaptive response to oxidative stress. This study investigated the regulation of Nrf2 by G␣ 12 and G␣ 13 . A deficiency of G␣ 12 , but not of G␣ 13 , enhanced Nrf2 activity and target gene transactivation in embryo fibroblasts. In mice, G␣ 12 knockout activated Nrf2 and thereby facilitated heme catabolism to bilirubin and its glucuronosyl conjugations. An oligonucleotide microarray demonstrated the transactivation of Nrf2 target genes by G␣ 12 gene knockout. G␣ 12 deficiency reduced Jun N-terminal protein kinase (JNK)-dependent Nrf2 ubiquitination required for proteasomal degradation, and so did G␣ 13 deficiency. The absence of G␣ 12 , but not of G␣ 13 , increased protein kinase C ␦ (PKC ␦) activation and the PKC ␦-mediated serine phosphorylation of Nrf2. G␣ 13 gene knockout or knockdown abrogated the Nrf2 phosphorylation induced by G␣ 12 deficiency, suggesting that relief from G␣ 12 repression leads to the G␣ 13 -mediated activation of Nrf2. Constitutive activation of G␣ 13 promoted Nrf2 activity and target gene induction via Rho-mediated PKC ␦ activation, corroborating positive regulation by G␣ 13 . In summary, G␣ 12 and G␣ 13 transmit a JNK-dependent signal for Nrf2 ubiquitination, whereas G␣ 13 regulates Rho-PKC ␦-mediated Nrf2 phosphorylation, which is negatively balanced by G␣ 12 .

Section: Resultssupporting

confidence: 61%

Role of Gα₁₂ and Gα₁₃ as Novel Switches for the Activity of Nrf2, a Key Antioxidative Transcription Factor

Cho

Molecular and Cellular Biology

et al. 2007

Self Cite

“…The transfected cells were subjected to in vitro invasion and transwell migration assays. * Statistically different at P \ 0.01 level of p53 and its DNA-binding activity in mouse embryonic fibroblasts, and G a12 QL-and G a13 QL-promoted p53 accumulation in MCF10A cells [27]. We conducted the subsequent experiments to investigate the involvement of p53 in MMP-2 transcriptional activation by G a12/13 .…”

Section: Resultsmentioning

confidence: 99%

“…Small-interfering(si) RNAs: Knockdown of MMP-2, G a12/13 and p53 was performed [22,27] with siRNA molecules targeting MMP-2(Invitrogen, [28]), p53, G a12 or G a13 (Santa Cruz, CA, USA).…”

Section: Methodsmentioning

confidence: 99%

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The G12 family proteins upregulate matrix metalloproteinase-2 via p53 leading to human breast cell invasion

Jeong

Breast Cancer Res Treat

et al. 2010

Self Cite

Although mounting evidence suggests a role for G(12) proteins, G(α12) and G(α13), in tumor progression, a direct role of G(12) proteins has not been determined. This study aims to elucidate the molecular mechanism for a tumorigenic and invasive potential of G(α12) and G(α13) in MCF10A human breast epithelial cells. Here, we report, for the first time, that G(α12) and G(α13) induce upregulation of matrix metalloproteinase (MMP)-2 leading to the invasive and migratory phenotypes in MCF10A cells. We further show that p53 is an important transcription factor for induction of MMP-2 transcriptional activation by G(α12/13). G(α12/13)-induced MMP-2 upregulation, invasion, and migration are dependent on the activation of Ras, Rac1, MKK3/6, p38, and Akt. Using human breast tissue samples, we demonstrate that the expression levels of G(α12) and MMP-2 are strongly correlated with the pathogenically diagnosed cancer (P < 0.0001). Moreover, the expression of G(α12) shows a strong correlation with that of MMP-2 in human breast cancer tissues, implicating the in vivo tumorigenic potential of G(α12). Taken together, this study elucidated the role of G(12) proteins in regulating processes for MMP-2 expression and malignant phenotypic conversion of MCF10A human breast epithelial cells, providing a molecular basis for the promoting role of G(α12) and G(α13) in breast cell invasion.

“…Equally interesting, certain members of the G␣ protein superfamily have been recently shown to regulate p53 expression under nongenotoxic conditions. 23 One limitation of this study is that knockdown of p66shc was not limited to the endothelium. Therefore, although our findings strongly suggest that, in the context of pressor doses of Ang II, endothelial p66shc is the principal mediator of vasomotor dysfunction, we cannot completely exclude the role of p66shc expressed in the vascular smooth muscle and adventitial layers.…”

Section: Discussionmentioning

confidence: 98%

P53 Impairs Endothelium-Dependent Vasomotor Function Through Transcriptional Upregulation of P66shc

Jung

Naqvi

et al. 2008

Circulation Research

Abstract-The transcription factor, p53, and the adaptor protein, p66shc, both play essential roles in promoting oxidative stress in the vascular system. However, the relationship between the two in the context of endothelium-dependent vascular tone is unknown. Here, we report a novel, evolutionarily conserved, p53-mediated transcriptional mechanism that regulates p66shc expression and identify p53 as an important determinant of endothelium-dependent vasomotor function. We provide evidence of a p53 response element in the promoter of p66shc and show that angiotensin II-induced upregulation of p66shc in endothelial cells is dependent on p53.In addition, we demonstrate that downregulation of p66shc expression, as well as inhibition of p53 function in mice, mitigates angiotensin II-induced impairment of endothelium-dependent vasorelaxation, decrease in bioavailable nitric oxide, and hypertension. These findings reveal a novel p53-dependent transcriptional mechanism for the regulation of p66shc expression that is operative in the vascular endothelium and suggest that this mechanism is important in impairing endothelium-dependent vascular relaxation. Key Words: tumor suppressor p53 Ⅲ p66shc angiotensin II Ⅲ endothelial dysfunction P 66shc belongs to the shcA family of adaptor proteins. P66shc is structurally and functionally distinct from p52shc and p46shc, the other 2 members of this family. It has a unique N-terminal collagen homology (CH2) domain that is important in governing its activity, and it functions as a protein that promotes oxidative stress within cells and tissues. Cells lacking p66shc have reduced levels of oxidants, and mice deficient for p66shc are resistant to oxidative stresses, and have an extended lifespan. 1,2 In addition to living longer, p66shc-deficient mice are protected against age-associated and hyperglycemia-induced endothelial dysfunction and oxidative stress. 3,4 Similarly, downregulation of p66shc in normal blood vessels and cells increases endothelial NO synthase activity and improves endothelium-dependent vasorelaxation. 5 P66shc also promotes atherogenesis. P66shc-deficient mice have reduced susceptibility to atheroma formation when fed a high-fat diet. 6 Despite this growing body of evidence implicating p66shc in many pathophysiological states of the cardiovascular system, little information exists about the mechanisms that govern p66shc expression in the cardiovascular system and the relevance of these mechanisms to human cardiovascular disease states.The role that the tumor suppressor protein p53 plays in different cell types comprising the vascular wall, and in the overall pathogenesis of atherosclerosis, as well as in other vascular disorders that are not necessarily associated with atherosclerosis, is highly controversial. P53 is undetectable in normal vascular specimens, but is expressed in endothelial cells, smooth muscle cells, and macrophages of advanced human atherosclerosis. 7 In animal models of high-fat dietinduced atheroma formation, knockout of p53 results in an incre...