Project description:PTEN encodes a tumor suppressor with lipid and protein phosphatase activities whose dysfunction has been implicated in melanomagenesis; less is known about how its phosphatases regulate melanoma metastasis. We show that PTEN expression negatively correlates with metastatic progression in human melanoma samples and a PTEN-deficient mouse melanoma model. Wildtype PTEN expression inhibited melanoma cell invasiveness and metastasis in a dose-dependent manner, behaviors that specifically required PTEN protein phosphatase activity. PTEN phosphatase activity regulated metastasis through Entpd5. Entpd5 knockdown reduced metastasis and IGF1R levels while promoting ER stress. In contrast, Entpd5 overexpression promoted metastasis and enhanced IGF1R levels, while reducing ER stress. Moreover, Entpd5 expression was regulated by the ER stress sensor ATF6. Altogether, our data show that PTEN phosphatase activity inhibits metastasis by negatively regulating the Entpd5/IGF1R pathway through ATF6, thereby identifying novel candidate therapeutic targets for the treatmtreatingwith PTEN mutant melanoma.
Project description:PTEN is frequently mutated in a wide range of malignancies. Beyond suppressing tumorigenesis, PTEN is involved in multiple biological processes, and the complexity of PTEN function is partially attributed to PTEN family members including PTENα and PTENβ. Here, we report the identification of PTENε (also named as PTEN5), a novel N-terminal-extended PTEN isoform that suppresses tumor invasion and metastasis. We show that the translation of PTENε is initiated from the CUG816 codon within the 5’UTR region of PTEN mRNA. PTENε mainly localizes in the cell membrane, and physically associates with and dephosphorylates VASP and ACTR2, which govern filopodia formation and cell motility. We found that endogenous depletion of PTENε promotes filopodia formation and enhances the metastasis capacity of tumor cells. Overall, we identify a new isoform of PTEN with distinct localization and function compared to the known members of the PTEN family. These findings enrich the PTEN family constitution and advance our current understanding of the importance and diversity of PTEN functions.
Project description:PTEN (Phosphatase and TENsin homolog deleted on chromosome ten) is a major tumor suppressor gene that is frequently mutated or lost under cancerous conditions. PTEN is a dual-specificity phosphatase that negatively regulates the PI3K/AKT/mTOR signaling pathway at the plasma membrane (PM). Its functional regulation and cellular localization are known to be conformationally driven. Access to the PM is phospho-regulated by open and closed PTEN forms. However, clarifying the underlying structural mechanisms is still an open avenue of research. Here, we apply an integrative structural modeling approach, combining coarse-grained and all-atom molecular dynamics with experimental crosslinking mass spectrometry. Conformational exchange between an “eased” form and a “strained” form brings the protein’s phosphatase and C2 domains closer together, blocking the catalytic site, and affecting the loops involved in PM binding. Our full-length PTEN models, AlphaMissense, and RaSP were used to better predict the consequences of PTEN mutations.
Project description:Malignant melanoma is characterized by frequent metastasis, however specific changes that regulate this process have not been clearly delineated. Although it is well known that Wnt signaling is frequently dysregulated in melanoma, the functional implications of this observation are unclear. By modulating beta-catenin levels in a mouse model of melanoma that is based on melanocyte-specific Pten loss and BrafV600E mutation, we demonstrate that beta-catenin is a central mediator of melanoma metastasis to lymph node and lung. In addition to altering metastasis, beta-catenin levels control tumor differentiation and regulate both MAPK/Erk and PI3K/Akt signaling. Highly metastatic tumors with beta-catenin stabilization are very similar to a subset of human melanomas; together these findings establish Wnt signaling as a metastasis regulator in melanoma. MoGene-1_0-st-v1: Four samples total. Two biological replicates of uncultured Pten/Braf murine melanomas and two biological replicates of uncultured Pten/Braf/Bcat-STA murine melanomas. MoEx-1_0-st-v1: Two samples total. Dissociated tumor and FACS-enriched Pten/Braf and Pten/Braf/Bcat-STA murine melanoma.
Project description:The interplay between effector and regulatory T (Treg) cells is crucial for adaptive immunity, but how Treg control effector cell flexibility is elusive. We found that the phosphatase PTEN links Treg stability to the repression of TH1 and TFH (follicular helper) responses. Depletion of PTEN in Treg resulted in excessive TFH and germinal center responses and spontaneous inflammatory disease. These defects are considerably blocked by deletion of Interferon-γ, indicating coordinated control of TH1 and TFH responses. Mechanistically, PTEN maintains Treg stability and proper metabolic balance between glycolysis and mitochondrial fitness. Moreover, PTEN deficiency markedly upregulates mTORC2-Akt activity, and loss of this activity restores PTEN-deficient Treg function. Our studies establish a PTEN-mTORC2 axis that actively maintains Treg stability and coordinates Treg-mediated control of effector cell flexibility. We used microarrays to explore the gene expression profiles differentially expressed in CD4+CD25+Foxp3-YFP+ Treg cells from wild-type (WT; C57BL/6 crossed with Foxp3-Cre) and Ptenfl/flFoxp3-Cre (Ptenfl/fl mice crossed with Foxp3-Cre) mice
Project description:The PTEN tumor suppressor controls cell death and survival by regulating functions of various molecular targets. Whilst the role of PTEN lipid-phosphatase activity on PtdIns(3,4,5)P3 and inhibition of PI3K pathway is well characterized, the biological relevance of PTEN protein-phosphatase activity remains undefined. Using knock-in (KI) mice harbouring cancer-associated and functionally relevant missense mutations, we show that although loss of PTEN lipid-phosphatase function cooperates with oncogenic PI3K to promote rapid mammary tumorigenesis, the additional loss of PTEN protein-phosphatase activity triggered an extensive cell death response evident in early and advanced mammary tumors. Omics and drug-targeting studies revealed that PI3Ks act to reduce glucocorticoid receptor (GR) levels, which are rescued by loss of PTEN protein-phosphatase activity to restrain cell survival. The dual regulation of GR by PI3K and PTEN functions as a rheostat that can be exploited for the treatment of PTEN-loss driven cancers.
Project description:The interplay between effector and regulatory T (Treg) cells is crucial for adaptive immunity, but how Treg control effector cell flexibility is elusive. We found that the phosphatase PTEN links Treg stability to the repression of TH1 and TFH (follicular helper) responses. Depletion of PTEN in Treg resulted in excessive TFH and germinal center responses and spontaneous inflammatory disease. These defects are considerably blocked by deletion of Interferon-γ, indicating coordinated control of TH1 and TFH responses. Mechanistically, PTEN maintains Treg stability and proper metabolic balance between glycolysis and mitochondrial fitness. Moreover, PTEN deficiency markedly upregulates mTORC2-Akt activity, and loss of this activity restores PTEN-deficient Treg function. Our studies establish a PTEN-mTORC2 axis that actively maintains Treg stability and coordinates Treg-mediated control of effector cell flexibility.
Project description:To investigate the effects of PTEN activity on gene expression in 3D cultured glioblastoma cells and the contributions of PTEN's lipid and protein phosphatase activities to these effects. We expressed wild type PTEN, a catalytically dead mutant (C124S) or mutants selectively lacking protein or lipid phosphatase activity (Y138L and G129E respectively) in U87MG cells at physiological levels by transient unselected polyclonal lentiviral transduction. Cells were then seeded into 3D matrigel and RNA prepared after 15 hours.