PI3K/AKT activation induces PTEN ubiquitination and destabilization accelerating tumourigenesis.
Ontology highlight
ABSTRACT:
SUBMITTER: Lee MS
PROVIDER: S-EPMC4518267 | biostudies-literature | 2015 Jul
REPOSITORIES: biostudies-literature
Publications
PI3K/AKT activation induces PTEN ubiquitination and destabilization accelerating tumourigenesis.
Lee Min-Sik MS Jeong Man-Hyung MH Lee Hyun-Woo HW Han Hyun-Ji HJ Ko Aram A Hewitt Stephen M SM Kim Jae-Hoon JH Chun Kyung-Hee KH Chung Joon-Yong JY Lee Cheolju C Cho Hanbyoul H Song Jaewhan J
Nature communications 20150717
The activity of the phosphatase and tensin homologue (PTEN) is known to be suppressed via post-translational modification. However, the mechanism and physiological significance by which post-translational modifications lead to PTEN suppression remain unclear. Here we demonstrate that PTEN destabilization is induced by EGFR- or oncogenic PI3K mutation-mediated AKT activation in cervical cancer. EGFR/PI3K/AKT-mediated ubiquitination and degradation of PTEN are dependent on the MKRN1 E3 ligase. The ...[more]
Similar Datasets
Project description:The PTEN tumor suppressor is a lipid phosphatase that has a central role in regulating the phosphatidylinositol-3-kinase (PI3K) signal transduction cascade. Nevertheless, the mechanism by which the PTEN activity is regulated in cells needs further elucidation. Although previous studies have shown that ubiquitination of PTEN can modulate its stability and subcellular localization, the role of ubiquitination in the most critical aspect of PTEN function, its phosphatase activity, has not been fully addressed. Here, we identify a novel E3 ubiquitin ligase of PTEN, Ret finger protein (RFP), that is able to promote atypical polyubiquitinations of PTEN. These ubiquitinations do not lead to PTEN instability or relocalization, but rather significantly inhibit PTEN phosphatase activity and therefore modulate its ability to regulate the PI3K signal transduction cascade. Indeed, RFP overexpression relieves PTEN-mediated inhibitory effects on AKT activation; in contrast, RNAi-mediated knockdown of endogenous RFP enhances the ability of PTEN to suppress AKT activation. Moreover, RFP-mediated ubiquitination of PTEN inhibits PTEN-dependent activation of TRAIL expression and also suppresses its ability to induce apoptosis. Our findings demonstrate a crucial role of RFP-mediated ubiquitination in controlling PTEN activity.
| S-EPMC3616435 | biostudies-literature
Project description:BackgroundMYCN amplification as a common genetic alteration that correlates with a poor prognosis for neuroblastoma (NB) patients. However, given the challenge of directly targeting MYCN, indirect strategies to modulate MYCN by interfering with its cofactors are attractive in NB treatment. Although cyclin B1 interacting protein 1 (CCNB1IP1) has been found to be upregulated in MYCN-driven mouse NB tissues, its regulation with MYCN and collaboration in driving the biological behaviour of NB remains unknown.MethodsTo evaluate the expression and clinical significance of CCNB1IP1 in NB patients, public datasets, clinical NB samples and cell lines were explored. MTT, EdU incorporation, colony and tumour sphere formation assays, and a mouse xenograft tumour model were utilized to examine the biological function of CCNB1IP1. The reciprocal manipulation of CCNB1IP1 and MYCN and the underlying mechanisms involved were investigated by gain- and loss-of-function approaches, dual-luciferase assay, chromatin immunoprecipitation (CHIP) and co-immunoprecipitation (Co-IP) experiments.ResultsCCNB1IP1 was upregulated in MYCN-amplified (MYCN-AM) NB cell lines and patients-derived tumour tissues, which was associated with poor prognosis. Phenotypic studies revealed that CCNB1IP1 facilitated the proliferation and tumourigenicity of NB cells in cooperation with MYCN in vitro and in vivo. Mechanistically, MYCN directly mediates the transcription of CCNB1IP1, which in turn attenuated the ubiquitination and degradation of MYCN protein, thus enhancing CCNB1IP1-MYCN cooperativity. Moreover, CCNB1IP1 competed with F box/WD-40 domain protein 7 (FBXW7) for MYCN binding and enabled MYCN-mediated tumourigenesis in a C-terminal domain-dependent manner.ConclusionsOur study revealed a previously uncharacterized mechanism of CCNB1IP1-mediated MYCN protein stability and will provide new prospects for precise treatment of MYCN-AM NB based on MYCN-CCNB1IP1 interaction.
| S-EPMC10352605 | biostudies-literature
Project description:Loss of PTEN tumor suppressor enhances metastatic risk in breast cancer, although the underlying mechanisms are poorly defined. We report that homozygous deletion of PTEN in mammary epithelial cells induces tubulin-based microtentacles (McTNs) that facilitate cell reattachment and homotypic aggregation. Treatment with contractility-modulating drugs showed that McTNs in PTEN(-/-) cells are suppressible by controlling the actin cytoskeleton. Because outward microtubule extension is counteracted by actin cortical contraction, increased activity of actin-severing proteins could release constraints on McTN formation in PTEN(-/-) cells. One such actin-severing protein, cofilin, is activated in detached PTEN(-/-) cells that could weaken the actin cortex to promote McTNs. Expression of wild-type cofilin, an activated mutant (S3A), and an inactive mutant (S3E) demonstrated that altering cofilin phosphorylation directly affects McTNs formation. Chemical inhibition of PI3K did not reduce McTNs or inactivate cofilin in PTEN(-/-) cells. Additionally, knock-in expression of the two most common PI3K-activating mutations observed in human cancer patients did not increase McTNs or activate cofilin. PTEN loss and PI3K activation also caused differential activation of the cofilin regulators, LIM-kinase1 (LIMK) and Slingshot-1L (SSH). Furthermore, McTNs were suppressed and cofilin was inactivated by restoration of PTEN in the PTEN(-/-) cells, indicating that both the elevation of McTNs and the activation of cofilin are specific results arising from PTEN loss. These data identify a novel mechanism by which PTEN loss could remodel the cortical actin network to facilitate McTNs that promote tumor cell reattachment and aggregation. Using isogenic MCF-10A PTEN(-/-) and PIK3CA mutants, we have further demonstrated that there are clear differences in activation of cofilin, LIMK and SSH between PTEN loss and PI3K activation, providing a new evidence that these mutations yield distinct cytoskeletal phenotypes, which could have an impact on tumor biology.
| S-EPMC3671600 | biostudies-literature
Project description:Background:Formononetin (FMN) is an isoflavone that produces arterial vasodilation. However, the underlying molecular mechanisms are unclear. Purpose:The purpose of this study was to explore the vasorelaxant effect and the potential mechanism of FMN in vascular endothelium in isolated rat aorta. Methods:The thoracic aortas of Sprague Dawley rats were isolated to test the arterial reactivity in the presence of FMN with or without inhibitors. Bioinformatics analyses, including a Bioinformatics Analysis Tool for Molecular Mechanism of Traditional Chinese Medicine and molecular docking methods, were performed to predict therapeutic targets responsible for the vascular protection produced by FMN. We used rat aortic endothelial cells (RAOECs) as an in vitro model to verify the potential mechanism through molecular biological analyses. The production of nitric oxide (NO) metabolites were evaluated via an NO assay kit according to the manufacturer's instruction. The mRNA expression of eNOS was analyzed by polymerase chain reaction, and the protein levels of PTEN, phosphorylated Akt, and eNOS were measured by Western blot. Results:We found that FMN dilated rat aortic rings in a concentration-dependent manner, which was reduced by endothelium denudation and eNOS inhibition. The bioinformatics analyses indicated that FMN activity was associated with the PI3K/PTEN/Akt signaling pathway. Molecular biological studies demonstrated that FMN significantly elevated the levels of NO and eNOS mRNA and markedly increased the protein expression of phosphorylated Akt and eNOS in RAOECs, and decreased PTEN compared with a dimethyl sulfoxide group. Conclusion:FMN performs vasorelaxation of the thoracic aorta through activating the PI3K/PTEN/Akt signaling pathway.
| S-EPMC6219413 | biostudies-literature
Project description:PARK2 is a gene implicated in disease states with opposing responses in cell fate determination, yet its contribution in pro-survival signaling is largely unknown. Here we show that PARK2 is altered in over a third of all human cancers, and its depletion results in enhanced phosphatidylinositol 3-kinase/Akt (PI3K/Akt) activation and increased vulnerability to PI3K/Akt/mTOR inhibitors. PARK2 depletion contributes to AMPK-mediated activation of endothelial nitric oxide synthase (eNOS), enhanced levels of reactive oxygen species, and a concomitant increase in oxidized nitric oxide levels, thereby promoting the inhibition of PTEN by S-nitrosylation and ubiquitination. Notably, AMPK activation alone is sufficient to induce PTEN S-nitrosylation in the absence of PARK2 depletion. Park2 loss and Pten loss also display striking cooperativity to promote tumorigenesis in vivo. Together, our findings reveal an important missing mechanism that might account for PTEN suppression in PARK2-deficient tumors, and they highlight the importance of PTEN S-nitrosylation in supporting cell survival and proliferation under conditions of energy deprivation.
| S-EPMC5426642 | biostudies-literature
Project description:The present study aimed to investigate the effects of microRNA (miR)?21 on osteoclastogenesis and its underlying molecular mechanisms. The expression levels of tartrate?resistant acid phosphatase (TRAP) and miR?21 were detected during osteoclastogenesis in receptor activator of NF??B ligand (RANKL)?induced RAW264.7 cells via reverse transcription?quantitative PCR. Bioinformatics and dual luciferase reporter assays were performed to analyze the association between miR?21 and Pten. RANKL?induced RAW264.7 cells were divided into the following groups: MiR?negative control (NC), miR?21 mimic, miR?21 inhibitor and miR?21 mimic + LY294002. The effects of miR?21 on osteoclastogenesis and bone resorption were then detected using TRAP staining and a bone resorption assay. Pten, phosphorylated?Akt and nuclear factor of activated T cell (NFATc1) expression levels were measured by western blotting to analyze the effects of miR?21 on the PI3K/Akt signaling pathway. The present study revealed that miR?21 was upregulated during osteoclastogenesis in RANKL?induced RAW264.7 cells. Furthermore, miR?21 negatively regulated Pten. Compared with the miR?negative control (NC) group, the number of osteoclasts and the percentage of bone resorption were increased in the miR?21 mimic group, whereas they were decreased in the miR?21 inhibitor group. The number of osteoclasts and the percentage of bone resorption in the miR?21 mimic + LY294002 group were lower than in the miR?21 mimic group. Compared with the miR?NC group, the protein expression levels of Pten were decreased, whereas p?Akt and NFATc1 were increased in the miR?21 mimic group. Conversely, Pten protein expression was increased, whereas p?Akt and NFATc1 were decreased in the miR?21 inhibitor group. In the miR?21 mimic + LY294002 group, Pten protein expression was higher, and p?Akt and NFATc1 were lower than in the miR?21 mimic group. In conclusion, miR?21 is upregulated during osteoclastogenesis, and may promote osteoclastogenesis and bone resorption through activating the PI3K/Akt signaling pathway via targeting Pten.
| S-EPMC7003029 | biostudies-literature
Project description:Altered lipid metabolism is increasingly recognized as a signature of cancer cells. Enabled by label-free Raman spectromicroscopy, we performed quantitative analysis of lipogenesis at single-cell level in human patient cancerous tissues. Our imaging data revealed an unexpected, aberrant accumulation of esterified cholesterol in lipid droplets of high-grade prostate cancer and metastases. Biochemical study showed that such cholesteryl ester accumulation was a consequence of loss of tumor suppressor PTEN and subsequent activation of PI3K/AKT pathway in prostate cancer cells. Furthermore, we found that such accumulation arose from significantly enhanced uptake of exogenous lipoproteins and required cholesterol esterification. Depletion of cholesteryl ester storage significantly reduced cancer proliferation, impaired cancer invasion capability, and suppressed tumor growth in mouse xenograft models with negligible toxicity. These findings open opportunities for diagnosing and treating prostate cancer by targeting the altered cholesterol metabolism.
| S-EPMC3969850 | biostudies-literature
Project description:Loss of PTEN, a negative regulator of the phosphoinositide 3-kinase signaling pathway, is a frequent event in T-cell acute lymphoblastic leukemia, suggesting the importance of phosphoinositide 3-kinase activity in this disease. Indeed, hyperactivation of the phosphoinositide 3-kinase pathway is associated with the disease aggressiveness, poor prognosis and resistance to current therapies. To identify a molecular pathway capable of cooperating with PTEN deficiency to drive oncogenic transformation of leukocytes, we performed an unbiased transformation screen with a library of tyrosine kinases. We found that activation of NTRK2 is able to confer a full growth phenotype of Ba/F3 cells in an IL3-independent manner in the PTEN-null setting. NTRK2 activation cooperates with PTEN deficiency through engaging both phosphoinositide3-kinase/AKT and JAK/STAT3 pathway activation in leukocytes. Notably, pharmacological inhibition demonstrated that p110α and p110δ are the major isoforms mediating the phosphoinositide 3-kinase/AKT signaling driven by NTRK2 activation in PTEN-deficient leukemia cells. Furthermore, combined inhibition of phosphoinositide 3-kinase and STAT3 significantly suppressed proliferation of PTEN-mutant T-cell acute lymphoblastic leukemia both in culture and in mouse xenografts. Together, our data suggest that a unique conjunction of PTEN deficiency and NTRK2 activation in T-cell acute lymphoblastic leukemia, and combined pharmacologic inhibition of phosphoinositide 3-kinase and STAT3 signaling may serve as an effective and durable therapeutic strategy for T-cell acute lymphoblastic leukemia.
| S-EPMC5029543 | biostudies-literature
Project description:The PI3K/AKT/mTOR signaling pathway is constitutively active in PTEN-deficient cancer cells, and its targeted inhibition has significant anti-tumor effects. However, the efficacy of targeted therapies is often limited due to drug resistance. The relevant signaling pathways in PTEN-deficient cancer cells treated with the PI3K/mTOR inhibitor BEZ235 were screened using a phosphokinase array, and further validated following treatment with multiple PI3K/AKT/mTOR inhibitors or AKT knockdown. The correlation between PTEN expression levels and STAT3 kinase phosphorylation in the tissue microarrays of gastric cancer patients was analyzed by immunohistochemistry. Cell proliferation and clonogenic assays were performed on the suitably treated PTEN-deficient cancer cells. Cytokine arrays, small molecule inhibition and knockdown assays were performed to identify related factors. PTEN-deficient tumor xenografts were established in nude mice that were treated with PI3K/AKT/mTOR and/or STAT3 inhibitors. PTEN deficiency was positively correlated with low STAT3 activity. PI3K/mTOR inhibitors increased the expression and secretion of macrophage migration inhibitory factor (MIF) and activated the JAK1/STAT3 signaling pathway. Both cancer cells and in vivo tumor xenografts showed that the combined inhibition of PI3K/AKT/mTOR and STAT3 activity enhanced the inhibitory effect of BEZ235 on the proliferation of PTEN-deficient cancer cells. Our findings provide a scientific basis for a novel treatment strategy in cancer patients with PTEN deficiency.
| S-EPMC7801611 | biostudies-literature
Project description:The mammalian signalling pathway involving class I PI3K (phosphoinositide 3-kinase), PTEN (phosphatidylinositol 3-phosphatase) and PKB (protein kinase B)/c-Akt has roles in multiple processes, including cell proliferation and apoptosis. To facilitate novel approaches for genetic, molecular and pharmacological analyses of these proteins, we have reconstituted this signalling pathway by heterologous expression in the unicellular eukaryote, Saccharomyces cerevisiae (yeast). High-level expression of the p110 catalytic subunit of mammalian PI3K dramatically inhibits yeast cell growth. This effect depends on PI3K kinase activity and is reversed partially by a PI3K inhibitor (LY294002) and reversed fully by co-expression of catalytically active PTEN (but not its purported yeast orthologue, Tep1). Growth arrest by PI3K correlates with loss of PIP2 (phosphatidylinositol 4,5-bisphosphate) and its conversion into PIP3 (phosphatidylinositol 3,4,5-trisphosphate). PIP2 depletion causes severe rearrangements of actin and septin architecture, defects in secretion and endocytosis, and activation of the mitogen-activated protein kinase, Slt2. In yeast producing PIP3, PKB/c-Akt localizes to the plasma membrane and its phosphorylation is enhanced. Phospho-specific antibodies show that both active and kinase-dead PKB/c-Akt are phosphorylated at Thr308 and Ser473. Thr308 phosphorylation, but not Ser473 phosphorylation, requires the yeast orthologues of mammalian PDK1 (3-phosphoinositide-dependent protein kinase-1): Pkh1 and Pkh2. Elimination of yeast Tor1 and Tor2 function, or of the related kinases (Tel1, Mec1 and Tra1), did not block Ser473 phosphorylation, implicating another kinase(s). Reconstruction of the PI3K/PTEN/Akt pathway in yeast permits incisive study of these enzymes and analysis of their functional interactions in a simplified context, establishes a new tool to screen for novel agonists and antagonists and provides a method to deplete PIP2 uniquely in the yeast cell.
| S-EPMC1198941 | biostudies-literature