RESUMEN
Internal tandem duplication in Fms-like tyrosine kinase 3 (FLT3-ITD) is the most frequent mutation observed in acute myeloid leukemia (AML) and correlates with poor prognosis. FLT3 tyrosine kinase inhibitors are promising for targeted therapy. Here, we investigated mechanisms dampening the response to the FLT3 inhibitor quizartinib, which is specific to the hematopoietic niche. Using AML primary samples and cell lines, we demonstrate that convergent signals from the hematopoietic microenvironment drive FLT3-ITD cell resistance to quizartinib through the expression and activation of the tyrosine kinase receptor AXL. Indeed, cytokines sustained phosphorylation of the transcription factor STAT5 in quizartinib-treated cells, which enhanced AXL expression by direct binding of a conserved motif in its genomic sequence. Likewise, hypoxia, another well-known hematopoietic niche hallmark, also enhanced AXL expression. Finally, in a xenograft mouse model, inhibition of AXL significantly increased the response of FLT3-ITD cells to quizartinib exclusively within a bone marrow environment. These data highlight a new bypass mechanism specific to the hematopoietic niche that hampers the response to quizartinib through combined upregulation of AXL activity. Targeting this signaling offers the prospect of a new therapy to eradicate resistant FLT3-ITD leukemic cells hidden within their specific microenvironment, thereby preventing relapses from FLT3-ITD clones.
Asunto(s)
Benzotiazoles/farmacología , Resistencia a Antineoplásicos , Leucemia Mieloide Aguda/metabolismo , Compuestos de Fenilurea/farmacología , Proteínas Proto-Oncogénicas/biosíntesis , Proteínas Tirosina Quinasas Receptoras/biosíntesis , Factor de Transcripción STAT5/metabolismo , Microambiente Tumoral , Tirosina Quinasa 3 Similar a fms/metabolismo , Hipoxia de la Célula , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Regulación Leucémica de la Expresión Génica/efectos de los fármacos , Humanos , Células K562 , Leucemia Mieloide Aguda/tratamiento farmacológico , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patología , Proteínas Proto-Oncogénicas/genética , Proteínas Tirosina Quinasas Receptoras/genética , Factor de Transcripción STAT5/genética , Regulación hacia Arriba/efectos de los fármacos , Tirosina Quinasa 3 Similar a fms/genética , Tirosina Quinasa del Receptor AxlRESUMEN
The prion protein is infamous for its involvement in a group of neurodegenerative diseases known as Transmissible Spongiform Encephalopathies. In the longstanding quest to decipher the physiological function of its cellular isoform, PrPC , the discovery of its participation to the self-renewal of hematopoietic and neural stem cells has cast a new spotlight on its potential role in stem cell biology. However, still little is known on the cellular and molecular mechanisms at play. Here, by combining in vitro and in vivo murine models of PrPC depletion, we establish that PrPC deficiency severely affects the Notch pathway, which plays a major role in neural stem cell maintenance. We document that the absence of PrPC in a neuroepithelial cell line or in primary neurospheres is associated with drastically reduced expression of Notch ligands and receptors, resulting in decreased levels of Notch target genes. Similar alterations of the Notch pathway are recovered in the neuroepithelium of Prnp-/- embryos during a developmental window encompassing neural tube closure. In addition, in line with Notch defects, our data show that the absence of PrPC results in altered expression of Nestin and Olig2 as well as N-cadherin distribution. We further provide evidence that PrPC controls the expression of the epidermal growth factor receptor (EGFR) downstream from Notch. Finally, we unveil a negative feedback action of EGFR on both Notch and PrPC . As a whole, our study delineates a molecular scenario through which PrPC takes part to the self-renewal of neural stem and progenitor cells. Stem Cells 2017;35:754-765.
Asunto(s)
Células-Madre Neurales/metabolismo , Proteínas Priónicas/metabolismo , Receptores Notch/metabolismo , Transducción de Señal , Animales , Biomarcadores/metabolismo , Cadherinas/metabolismo , Comunicación Celular , Línea Celular , Linaje de la Célula , Embrión de Mamíferos/metabolismo , Desarrollo Embrionario , Receptores ErbB/metabolismo , Retroalimentación Fisiológica , RatonesRESUMEN
Defining the function of the genes that, like RUNX1, are deregulated in blood cell malignancies represents an important challenge. Myeloid leukemia factors (MLFs) constitute a poorly characterized family of conserved proteins whose founding member, MLF1, has been associated with acute myeloid leukemia in humans. To gain insight into the functions of this family, we investigated the role of the Drosophila MLF homolog during blood cell development. Here we report that mlf controls the homeostasis of the Drosophila hematopoietic system. Notably, mlf participates in a positive feedback loop to fine tune the activity of the RUNX transcription factor Lozenge (LZ) during development of the crystal cells, one of the two main blood cell lineages in Drosophila. At the molecular level, our data in cell cultures and in vivo strongly suggest that MLF controls the number of crystal cells by protecting LZ from degradation. Remarkably, it appears that the human MLF1 protein can substitute for MLF in the crystal cell lineage. In addition, MLF stabilizes the human oncogenic fusion protein RUNX1-ETO and is required for RUNX1-ETO-induced blood cell disorders in a Drosophila model of leukemia. Finally, using the human leukemic blood cell line Kasumi-1, we show that MLF1 depletion impairs RUNX1-ETO accumulation and reduces RUNX1-ETO-dependent proliferation. Thus, we propose that the regulation of RUNX protein levels is a conserved feature of MLF family members that could be critical for normal and pathological blood cell development.
Asunto(s)
Secuencia Conservada/genética , Subunidades alfa del Factor de Unión al Sitio Principal/metabolismo , Proteínas de Unión al ADN/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Hematopoyesis , Factores de Transcripción/metabolismo , Animales , Linaje de la Célula , Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Drosophila melanogaster/citología , Drosophila melanogaster/embriología , Embrión no Mamífero/citología , Embrión no Mamífero/metabolismo , Humanos , Larva/citología , Larva/metabolismo , Proteínas de Fusión Oncogénica/metabolismo , Fenotipo , Estabilidad Proteica , Proteolisis , Activación Transcripcional/genéticaRESUMEN
Patients with EGFR-mutated non-small cell lung cancer (NSCLC) benefit from treatment with tyrosine kinase inhibitors (TKI) targeting EGFR. Despite improvements in patient care, especially with the 3rd generation TKI osimertinib, disease relapse is observed in all patients. Among the various processes involved in TKI resistance, epithelial-to-mesenchymal transition (EMT) is far from being fully characterized. We hypothesized that the cellular prion protein PrPC could be involved in EMT and EGFR-TKI resistance in NSCLC. Using 5 independent lung adenocarcinoma datasets, including our own cohort, we document that the expression of the PRNP gene encoding PrPC is associated with EMT. By manipulating the levels of PrPC in different EGFR-mutated NSCLC cell lines, we firmly establish that the expression of PrPC is mandatory for cells to maintain or acquire a mesenchymal phenotype. Mechanistically, we show that PrPC operates through an ILK-RBPJ cascade, which also controls the expression of EGFR. Our data further demonstrate that PrPC levels are elevated in EGFR-mutated versus wild-type tumours or upon EGFR activation in vitro. In addition, we provide evidence that PRNP levels increase with TKI resistance and that reducing PRNP expression sensitizes cells to osimertinib. Finally, we found that plasma PrPC levels are increased in EGFR-mutated NSCLC patients from 2 independent cohorts and that their longitudinal evolution mirrors that of disease. Altogether, these findings define PrPC as a candidate driver of EMT-dependent resistance to EGFR-TKI in NSCLC. They further suggest that monitoring plasma PrPC levels may represent a valuable non-invasive strategy for patient follow-up and warrant considering PrPC-targeted therapies for EGFR-mutated NSCLC patients with TKI failure.
RESUMEN
The cellular prion protein PrPC partners with caveolin-1 (CAV1) in neurodegenerative diseases but whether this interplay occurs in cancer has never been investigated. By leveraging patient and cell line datasets, we uncover a molecular link between PrPC and CAV1 across cancer. Using cell-based assays, we show that PrPC regulates the expression of and interacts with CAV1. PrPC additionally controls the expression of the amyloid precursor protein APP and of the Aß generating enzyme BACE1, and regulates the levels of Aß, whose accumulation is a central event in Alzheimer's disease. We further identify DKK1 and DKK3, involved in both Alzheimer's disease and cancer progression, as targets of the PrPC-dependent axis. Finally, we establish that antibody-mediated blocking of the Aß-PrPC interaction delays the growth of prostate cancer cell line-derived xenografts and prevents the development of metastases. Our data additionally support an enrichment of the Aß-PrPC-dependent pathway in the basal subtype of prostate cancer, associated with anti-hormonal therapy resistance, and in mesenchymal colon cancer, associated with poor prognosis. Thus, based on a parallel with neurodegenerative diseases, our results bring to light an Aß-PrPC axis and support the potential of targeting this pathway in patients with selected subtypes of prostate and colon cancer.
Asunto(s)
Enfermedad de Alzheimer , Neoplasias del Colon , Neoplasias de la Próstata , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Péptidos beta-Amiloides/química , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Ácido Aspártico Endopeptidasas/metabolismo , Caveolina 1/genética , Caveolina 1/metabolismo , Neoplasias del Colon/genética , Humanos , Masculino , Proteínas Priónicas/genética , Proteínas Priónicas/metabolismo , Neoplasias de la Próstata/genéticaRESUMEN
BACKGROUND: Low miR-31-3p expression was identified as predictive of anti-EGFR efficacy in RAS-wt mCRC. Primary tumor side was also proposed as a predictive factor of anti-EGFR benefit. This retrospective multicentric study evaluated the predictive role of miR-31-3p in right-sided RAS-wt mCRC patients treated with first-line CT+anti-EGFR or CT+bevacizumab (Beva). METHODS: Seventy-two right-sided RAS-wt mCRC patients treated in first-line with CT+anti-EGFR (n = 43) or Beva (n = 29) were included. Overall survival (OS), progression-free survival (PFS) and response rate (RR) were analyzed and stratified according to tumor miR-31-3p expression level and targeted therapy (TT). RESULTS: BRAF V600E mutation was more frequent in high vs low miR-31-3p expressers (60.6% vs 15.4%, P < 0.001). PFS was significantly longer with CT+Beva than with CT+anti-EGFR (13 vs 7 months; P = 0.024). Among low miR-31-3p expressers, PFS, OS and RR were not significantly different between the two groups, while in high miR-31-3p expressers, only PFS was longer in the CT+Beva group (11 vs 6 months; P = 0.03). In patients treated with CT+anti-EGFR, low miR-31-3p expressers had a significantly longer OS (20 vs 13 months; P = 0.02) than high miR-31-3p expressers. ORR was not significantly different between the two groups of treatment, in both low and high miR-31-3p expressers. MiR-31-3p expression status was statistically correlated between primary tumors and corresponding metastases. CONCLUSION: In this study, miR-31-3p couldn't identify a subgroup of patients with right-sided RAS-wt mCRC who might benefit from anti-EGFR and suggest that Beva is the TT of choice in first-line treatment of these patients.
Asunto(s)
Neoplasias del Colon , Neoplasias Colorrectales , MicroARNs , Protocolos de Quimioterapia Combinada Antineoplásica , Bevacizumab/uso terapéutico , Neoplasias del Colon/tratamiento farmacológico , Neoplasias del Colon/genética , Neoplasias Colorrectales/patología , Receptores ErbB/genética , Humanos , MicroARNs/genética , Estudios RetrospectivosRESUMEN
Glioblastoma (GBM), the highest-grade form of gliomas, is the most frequent and the most aggressive. Recently, a subpopulation of cells with stem cells characteristics, commonly named "tumor-initiating stem cells" (TISCs) or "cancer stem cells" (CSCs) were identified in GBM. These cells were shown to be highly resistant to chemotherapeutic drugs and to ionizing radiations. Consequently, the knowledge of the signals that regulate the functions and survival of TISCs is crucial. In our work, we describe a neurosphere-initiating cell (NS-IC) assay to quantify TISC/CSCs from patients with GBM and show that these cells are tumorigenic in vivo. We demonstrate that the intracellular signal transducer and activator of transcription STAT3 is constitutively activated by phosphorylation preferentially on serine 727 in these cells. Moreover, we demonstrate that the selective inhibition of STAT3 by the chemical compound Stattic or by siRNA STAT3 abrogates TISC/CSC proliferation and NS-IC suggesting that self-renewal of GBM "stem-like" cells depends on the presence of STAT3 for their maintenance. Finally, we show that inhibition of STAT3 by Stattic sensitizes TISC/CSCs to the inhibitory action of Temozolomide with a strong synergistic effect of both drugs. Overall, these results suggest that strategies focused on STAT3 inhibition are efficient at the level of "stem-like" cells and could be of interest for therapeutic purposes in patients with malignant GBM.
Asunto(s)
Glioblastoma/metabolismo , Células Madre Neoplásicas/metabolismo , Células-Madre Neurales/metabolismo , Factor de Transcripción STAT3/metabolismo , Animales , Antineoplásicos Alquilantes/farmacología , Apoptosis/efectos de los fármacos , Western Blotting , Proliferación Celular/efectos de los fármacos , Óxidos S-Cíclicos/farmacología , Dacarbazina/análogos & derivados , Dacarbazina/farmacología , Sinergismo Farmacológico , Citometría de Flujo , Técnica del Anticuerpo Fluorescente , Glioblastoma/genética , Glioblastoma/patología , Humanos , Ratones , Ratones Desnudos , Células Madre Neoplásicas/efectos de los fármacos , Células Madre Neoplásicas/patología , Células-Madre Neurales/efectos de los fármacos , Células-Madre Neurales/patología , Fosforilación/efectos de los fármacos , ARN Mensajero/genética , ARN Interferente Pequeño/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factor de Transcripción STAT3/antagonistas & inhibidores , Temozolomida , Células Tumorales CultivadasRESUMEN
The D816V-mutated variant of Kit triggers multiple signaling pathways and is considered essential for malignant transformation in mast cell (MC) neoplasms. We here describe that constitutive activation of the Stat5-PI3K-Akt-cascade controls neoplastic MC development. Retrovirally transduced active Stat5 (cS5(F)) was found to trigger PI3K and Akt activation, and to transform murine bone marrow progenitors into tissue-infiltrating MCs. Primary neoplastic Kit D816V(+) MCs in patients with mastocytosis also displayed activated Stat5, which was found to localize to the cytoplasm and to form a signaling complex with PI3K, with consecutive Akt activation. Finally, the knock-down of either Stat5 or Akt activity resulted in growth inhibition of neoplastic Kit D816V(+) MCs. These data suggest that a downstream Stat5-PI3K-Akt signaling cascade is essential for Kit D816V-mediated growth and survival of neoplastic MCs.
Asunto(s)
Sistema de Señalización de MAP Quinasas , Mastocitosis Sistémica/patología , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-kit/fisiología , Factor de Transcripción STAT5/metabolismo , Animales , Células de la Médula Ósea , Estudios de Casos y Controles , Proliferación Celular , Células Madre Hematopoyéticas , Humanos , Infiltración Leucémica , Ratones , Mutación Missense , Proteínas Proto-Oncogénicas c-akt/metabolismo , Proteínas Proto-Oncogénicas c-kit/genéticaRESUMEN
Among the ever-growing number of self-replicating proteins involved in neurodegenerative diseases, the prion protein PrP remains the most infamous for its central role in transmissible spongiform encephalopathies (TSEs). In these diseases, pathogenic prions propagate through a seeding mechanism, where normal PrPC molecules are converted into abnormally folded scrapie isoforms termed PrPSc. Since its discovery over 30 years ago, much advance has contributed to define the host-encoded cellular prion protein PrPC as a critical relay of prion-induced neuronal cell demise. A current consensual view is that the conversion of PrPC into PrPSc in neuronal cells diverts the former from its normal function with subsequent molecular alterations affecting synaptic plasticity. Here, we report that prion infection is associated with reduced expression of key effectors of the Notch pathway in vitro and in vivo, recapitulating changes fostered by the absence of PrPC. We further show that both prion infection and PrPC depletion promote drastic alterations in the expression of a defined set of Eph receptors and their ephrin ligands, which represent important players in synaptic function. Our data indicate that defects in the Notch and Eph axes can be mitigated in response to histone deacetylase inhibition in PrPC-depleted as well as prion-infected cells. We thus conclude that infectious prions cause a loss-of-function phenotype with respect to Notch and Eph signaling and that these alterations are sustained by epigenetic mechanisms.
Asunto(s)
Enfermedades por Prión/metabolismo , Proteínas Priónicas/metabolismo , Receptores de la Familia Eph/metabolismo , Receptores Notch/metabolismo , Transducción de Señal/fisiología , Animales , Epigénesis Genética , Ratones , Neuronas/metabolismo , Enfermedades por Prión/genéticaRESUMEN
BACKGROUND: Comprehensive transcriptomic analyses have shown that colorectal cancer (CRC) is heterogeneous and have led to the definition of molecular subtypes among which the stem-cell, mesenchymal-like group is associated with poor prognosis. The molecular pathways orchestrating the emergence of this subtype are incompletely understood. In line with the contribution of the cellular prion protein PrPC to stemness, we hypothesize that deregulation of this protein could lead to a stem-cell, mesenchymal-like phenotype in CRC. METHODS: We assessed the distribution of the PrPC-encoding PRNP mRNA in two large CRC cohorts according to molecular classification and its association with patient survival. We developed cell-based assays to explore the impact of gain and loss of PrPC function on markers of the mesenchymal subtype and to delineate the signalling pathways recruited by PrPC. We measured soluble PrPC in the plasmas of 325 patients with metastatic CRC and probed associations with disease outcome. FINDINGS: We found that PRNP gene expression is enriched in tumours of the mesenchymal subtype and is associated with poor survival. Our in vitro analyses revealed that PrPC controls the expression of genes that specify the mesenchymal subtype through the recruitment of the Hippo pathway effectors YAP and TAZ and the TGFß pathway. We showed that plasma levels of PrPC are elevated in metastatic CRC and are associated with poor disease control. INTERPRETATION: Our findings define PrPC as a candidate driver of the poor-prognosis mesenchymal subtype of CRC. They suggest that PrPC may serve as a potential biomarker for patient stratification in CRC. FUNDING: Grant support was provided by the following: Cancéropôle Ile de France (grant number 2016-1-EMERG-36-UP 5-1), Association pour la Recherche sur le Cancer (grant number PJA 20171206220), SATT Ile de France Innov (grant number 415) as well as INSERM.
Asunto(s)
Neoplasias Colorrectales/genética , Neoplasias Colorrectales/patología , Transición Epitelial-Mesenquimal/genética , Proteínas Priónicas/genética , Adulto , Anciano , Anciano de 80 o más Años , Animales , Biomarcadores , Línea Celular Tumoral , Neoplasias Colorrectales/metabolismo , Neoplasias Colorrectales/mortalidad , Femenino , Expresión Génica , Vía de Señalización Hippo , Humanos , Estimación de Kaplan-Meier , Masculino , Persona de Mediana Edad , Proteínas Priónicas/metabolismo , Pronóstico , Proteínas Serina-Treonina Quinasas/metabolismo , ARN Mensajero/genética , Transducción de Señal , Factor de Crecimiento Transformador beta/metabolismoAsunto(s)
Leucemia Mielógena Crónica BCR-ABL Positiva/tratamiento farmacológico , Factor de Transcripción STAT5/fisiología , Antineoplásicos , Benzamidas/uso terapéutico , Supervivencia Celular , Resistencia a Antineoplásicos , Proteínas de Fusión bcr-abl/antagonistas & inhibidores , Proteínas de Fusión bcr-abl/fisiología , Genes abl/genética , Células Madre Hematopoyéticas/fisiología , Humanos , Mesilato de Imatinib , Leucemia Mielógena Crónica BCR-ABL Positiva/genética , Recurrencia Local de Neoplasia/prevención & control , Piperazinas/uso terapéutico , Inhibidores de Proteínas Quinasas , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Pirimidinas/uso terapéuticoRESUMEN
MiR-31-3p expression has been shown to be a predictive biomarker for response to anti-epithelial growth factor receptor therapy in patients with RAS wild-type metastatic colorectal cancer (mCRC). To aid in the quantification of miR-31-3p expression in formalin-fixed paraffin-embedded (FFPE) primary tumor samples from patients with mCRC, a reverse-transcription quantitative polymerase chain reaction (RT-qPCR) assay was developed and validated. Assay development included the identification of a microRNA reference standard and the determination of an appropriate relative quantification cutoff for differentiating low versus high miR-31-3p expression. Sample specimens for the validation studies included both FFPE slides and shavings. Polymerase chain reaction (PCR) efficiency and linearity, analytical sensitivity and specificity, assay robustness, reproducibility, and accuracy were demonstrated across a number of test conditions and differing quantitative PCR platforms. The data from this study provide evidence as to the feasibility of quantifying the expression of miR-31-3p from FFPE tumor tissue using a standardized RT-qPCR assay.
RESUMEN
Although initially disregarded compared to prion pathogenesis, the functions exerted by the cellular prion protein PrPC have gained much interest over the past two decades. Research aiming at unraveling PrPC functions started to intensify when it became appreciated that it would give clues as to how it is subverted in the context of prion infection and, more recently, in the context of Alzheimer's disease. It must now be admitted that PrPC is implicated in an incredible variety of biological processes, including neuronal homeostasis, stem cell fate, protection against stress, or cell adhesion. It appears that these diverse roles can all be fulfilled through the involvement of PrPC in cell signaling events. Our aim here is to provide an overview of our current understanding of PrPC functions from the animal to the molecular scale and to highlight some of the remaining gaps that should be addressed in future research.
Asunto(s)
Proteínas Priónicas/metabolismo , Animales , Adhesión Celular , Diferenciación Celular , Sistema Nervioso Central/metabolismo , Matriz Extracelular/metabolismo , Humanos , Proteínas Priónicas/química , Transducción de SeñalRESUMEN
Although conversion of the cellular form of the prion protein (PrP(C)) into a misfolded isoform is the underlying cause of prion diseases, understanding PrP(C) physiological functions has remained challenging. PrP(C) depletion or overexpression alters the proliferation and differentiation properties of various types of stem and progenitor cells in vitro by unknown mechanisms. Such involvement remains uncertain in vivo in the absence of any drastic phenotype of mice lacking PrP(C). Here, we report PrP(C) enrichment at the base of the primary cilium in stem and progenitor cells from the central nervous system and cardiovascular system of developing mouse embryos. PrP(C) depletion in a neuroepithelial cell line dramatically altered key cilium-dependent processes, such as Sonic hedgehog signalling and α-tubulin post-translational modifications. These processes were also affected over a limited time window in PrP(C)-ablated embryos. Thus, our study reveals PrP(C) as a potential actor in the developmental regulation of microtubule dynamics and ciliary functions.
Asunto(s)
Cilios/metabolismo , Priones/metabolismo , Tubulina (Proteína)/metabolismo , Animales , Sistema Cardiovascular/metabolismo , Células Cultivadas , Sistema Nervioso Central/metabolismo , Embrión de Mamíferos/metabolismo , Desarrollo Embrionario , Proteínas Hedgehog/metabolismo , Ratones , Microscopía Confocal , Proteínas PrPC/deficiencia , Proteínas PrPC/genética , Priones/genética , Procesamiento Proteico-Postraduccional , ARN Mensajero/metabolismo , Transducción de Señal , Células Madre/citología , Células Madre/metabolismoRESUMEN
The cellular prion protein PrP(C) was identified over twenty-five years ago as the normal counterpart of the scrapie prion protein PrP(Sc), itself the main if not the sole component of the infectious agent at the root of Transmissible Spongiform Encephalopathies (TSEs). PrP(C) is a ubiquitous cell surface protein, abundantly expressed in neurons, which constitute the targets of PrP(Sc)-mediated toxicity. Converging evidence have highlighted that neuronal, GPI-anchored PrP(C) is absolutely required for prion-induced neuropathogenesis, which warrants investigating into the normal function exerted by PrP(C) in a neuronal context. It is now well-established that PrP(C) can serve as a cell signalling molecule, able to mobilize transduction cascades in response to interactions with partners. This function endows PrP(C) with the capacity to participate in multiple neuronal processes, ranging from survival to synaptic plasticity. A diverse array of data have allowed to shed light on how this function is corrupted by PrP(Sc). Recently, amyloid Aß oligomers, whose accumulation is associated with Alzheimer's disease (AD), were shown to similarly instigate toxic events by deviating PrP(C)-mediated signalling. Here, we provide an overview of the various signal transduction cascades ascribed to PrP(C) in neurons, summarize how their subversion by PrP(Sc) or Aß oligomers contributes to TSE or AD neuropathogenesis and discuss the ensuing clinical implications.
Asunto(s)
Neuronas/citología , Proteínas PrPC/metabolismo , Transducción de Señal , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Enfermedad de Alzheimer/terapia , Animales , Membrana Celular/metabolismo , Humanos , Neuronas/patología , Receptores de Neurotransmisores/metabolismoRESUMEN
The cellular prion protein PrP(c) is the normal counterpart of the scrapie prion protein PrP (Sc), the main component of the infectious agent of transmissible spongiform encephalopathies. The recent discovery that PrP (c) can serve as a receptor for the amyloid beta (Aß) peptide and relay its neurotoxicity is sparking renewed interest on this protein and its involvement in signal transduction processes. Disease-associated PrP (Sc) shares with Aß the ability to hijack PrP (c)-dependent signaling cascades, and thereby instigate pathogenic events. Among these is an impairment of Aß clearance, uncovered in prion-infected neuronal cells. These findings add another facet to the intricate interplay between PrP (c) and Aß. Here, we summarize the connection between PrP-mediated signaling and Aß clearance and discuss its pathological implications.
RESUMEN
The cellular prion protein, PrP(C), is a glycosylphosphatidylinositol-anchored protein, abundant in lipid rafts and highly expressed in the brain. While PrP(C) is much studied for its involvement under its abnormal PrP(Sc) isoform in Transmissible Spongiform Encephalopathies, its physiological role remains unclear. Here, we report that GSK3ß, a multifunctional kinase whose inhibition is neuroprotective, is a downstream target of PrP(C) signalling in serotonergic neuronal cells. We show that the PrP(C)-dependent inactivation of GSK3ß is relayed by a caveolin-Lyn platform located on neuronal cell bodies. Furthermore, the coupling of PrP(C) to GSK3ß potentiates serotonergic signalling by altering the distribution and activity of the serotonin 1B receptor (5-HT1BR), a receptor that limits neurotransmitter release. In vivo, our data reveal an increased GSK3ß kinase activity in PrP-deficient mouse brain, as well as sustained 5-HT1BR activity, whose inhibition promotes an anxiogenic behavioural response. Collectively, our data unveil a new facet of PrP(C) signalling that strengthens neurotransmission.
Asunto(s)
Caveolinas/metabolismo , Glucógeno Sintasa Quinasa 3/metabolismo , Neuronas/metabolismo , Priones/metabolismo , Receptor de Serotonina 5-HT1B/metabolismo , Animales , Línea Celular Tumoral , Glucógeno Sintasa Quinasa 3 beta , Masculino , Ratones , Ratones Endogámicos C57BL , Enfermedades por Prión/metabolismo , Unión Proteica/fisiología , Ratas , Transducción de Señal/fisiologíaRESUMEN
The cellular prion protein PrP(C) was initially discovered as the normal counterpart of the pathological scrapie prion protein PrP(Sc), the main component of the infectious agent of Transmissible Spongiform Encephalopathies. While clues as to the physiological function of this ubiquitous protein were greatly anticipated from the development of knockout animals, PrP-null mice turned out to be viable and to develop without major phenotypic abnormalities. Notwithstanding, the discovery that hematopoietic stem cells from PrP-null mice have impaired long-term repopulating potential has set the stage for investigating into the role of PrP(C) in stem cell biology. A wealth of data have now exemplified that PrP(C) is expressed in distinct types of stem cells and regulates their self-renewal as well as their differentiation potential. A role for PrP(C) in the fate restriction of embryonic stem cells has further been proposed. Paralleling these observations, an overexpression of PrP(C) has been documented in various types of tumors. In line with the contribution of PrP(C) to stemness and to the proliferation of cancer cells, PrP(C) was recently found to be enriched in subpopulations of tumor-initiating cells. In the present review, we summarize the current knowledge of the role played by PrP(C) in stem cell biology and discuss how the subversion of its function may contribute to cancer progression.
RESUMEN
The deletion of the cellular form of the prion protein (PrP(C)) in mouse, goat, and cattle has no drastic phenotypic consequence. This stands in apparent contradiction with PrP(C) quasi-ubiquitous expression and conserved primary and tertiary structures in mammals, and its pivotal role in neurodegenerative diseases such as prion and Alzheimer's diseases. In zebrafish embryos, depletion of PrP ortholog leads to a severe loss-of-function phenotype. This raises the question of a potential role of PrP(C) in the development of all vertebrates. This view is further supported by the early expression of the PrP(C) encoding gene (Prnp) in many tissues of the mouse embryo, the transient disruption of a broad number of cellular pathways in early Prnp(-/-) mouse embryos, and a growing body of evidence for PrP(C) involvement in the regulation of cell proliferation and differentiation in various types of mammalian stem cells and progenitors. Finally, several studies in both zebrafish embryos and in mammalian cells and tissues in formation support a role for PrP(C) in cell adhesion, extra-cellular matrix interactions and cytoskeleton. In this review, we summarize and compare the different models used to decipher PrP(C) functions at early developmental stages during embryo- and organo-genesis and discuss their relevance.
RESUMEN
STAT5 fulfills essential roles in hematopoietic stem cell (HSC) self-renewal and chronic myeloid leukemia (CML), a prototypical stem cell malignancy. However, the specific contributions of the two related genes STAT5A and STAT5B have not been determined. In this study, we used a RNAi-based strategy to establish participation of these genes to CML disease and persistence following targeted therapy. We showed that STAT5A/STAT5B double-knockdown triggers CML cell apoptosis and suppresses both normal and CML HSC long-term clonogenic potential. STAT5A and STAT5B exhibited similar prosurvival activity, but STAT5A attenuation alone was ineffective at impairing growth of normal and CML CD34(+) cells isolated at diagnosis. In contrast, STAT5A attenuation was sufficient to enhance basal oxidative stress and DNA damage of normal CD34(+) and CML cells. Furthermore, it weakened the ability to manage exogenous oxidative stress, increased p53 (TRP53)/CHK-2 (CHEK2) stress pathway activation, and enhanced prolyl hydroxylase domain (PHD)-3 (EGLN3) mRNA expression. Only STAT5A and its transactivation domain-deficient mutant STAT5AΔ749 specifically rescued these activities. STAT5A attenuation was also active at inhibiting growth of CML CD34(+) cells from patients with acquired resistance to imatinib. Our findings show that STAT5A has a selective role in contributing to stress resistance through unconventional mechanisms, offering new opportunities to eradicate the most primitive and tyrosine kinase inhibitor-resistant CML cells with an additional potential to eradicate persistent stem cell populations.