Met signaling in cardiomyocytes is required for normal cardiac function in adult mice

et al.Hepatocyte growth factor (HGF) and its receptor, Met, are key determinants of distinct developmental processes. Although HGF exerts cardio-protective effects in a number of cardiac pathologies, it remains unknown whether HGF/Met signaling is essential for myocardial development and/or physiological function in adulthood. We therefore investigated the requirement of HGF/Met signaling in cardiomyocyte for embryonic and postnatal heart development and function by conditional inactivation of the Met receptor in cardiomyocytes using the Cre-α-MHC mouse line (referred to as α-MHCMet-KO). Although α-MHCMet-KO mice showed normal heart development and were viable and fertile, by 6. months of age, males developed cardiomyocyte hypertrophy, associated with interstitial fibrosis. A significant upregulation in markers of myocardial damage, such as β-MHC and ANF, was also observed. By the age of 9. months, α-MHCMet-KO males displayed systolic cardiac dysfunction. Mechanistically, we provide evidence of a severe imbalance in the antioxidant defenses in α-MHCMet-KO hearts involving a reduced expression and activity of catalase and superoxide dismutase, with consequent reactive oxygen species accumulation. Similar anomalies were observed in females, although with a slower kinetics. We also found that Met signaling down-regulation leads to an increase in TGF-β production and a decrease in p38MAPK activation, which may contribute to phenotypic alterations displayed in α-MHCMet-KO mice. Consistently, we show that HGF acts through p38α to upregulate antioxidant enzymes in cardiomyocytes. Our results highlight that HGF/Met signaling in cardiomyocytes plays a physiological cardio-protective role in adult mice by acting as an endogenous regulator of heart function through oxidative stress control.This work was supported by grants: (AFM)-13683 from Association Française contre les myopathies, France, FIS-PI07/0071 and SAF-2010-20198-C02-01 from Ministry of Science and Innovation, Spain, and grants from Comunidad de Madrid/Universidad Complutense de Madrid: CAM/UCM 920384 and UCM-BSCH 920384, Spain to A.P.; BFU2011-25304 from Ministry of Science and Innovation, Spain, RD12/0019/0022 (TerCel network, ISCIII), P11-CTS-7564 (Junta de Andalucía) to R. M.-Ch.; FRM (Fondation pour la Recherche Médicale), Fondation Bettencourt-Schueller, and Association Française contre les myopathies (AFM) to F.M.; SAF2010-15881 from Ministry of Science and Innovation, Spain, and RD012/0021 (RedinRen network, ISCIII), and GR100 (Junta de Castilla y León) to J.M. L.-N. The cardiovascular phenotyping unit of the University of Salamanca, including the telemetry equipment, has been acquired with the support of the European Regional Development Funds (FEDER).Peer Reviewe

C3G downregulation induces the acquisition of a mesenchymal phenotype that enhances aggressiveness of glioblastoma cells

© The Author(s) 2021.Glioblastoma (GBM) is the most aggressive tumor from the central nervous system (CNS). The current lack of efficient therapies makes essential to find new treatment strategies. C3G, a guanine nucleotide exchange factor for some Ras proteins, plays a dual role in cancer, but its function in GBM remains unknown. Database analyses revealed a reduced C3G mRNA expression in GBM patient samples. C3G protein levels were also decreased in a panel of human GBM cell lines as compared to astrocytes. Based on this, we characterized C3G function in GBM using in vitro and in vivo human GBM models. We report here that C3G downregulation promoted the acquisition of a more mesenchymal phenotype that enhanced the migratory and invasive capacity of GBM cells. This facilitates foci formation in anchorage-dependent and -independent growth assays and the generation of larger tumors in xenografts and chick chorioallantoic membrane (CAM) assays, but with a lower cell density, as proliferation was reduced. Mechanistically, C3G knock-down impairs EGFR signaling by reducing cell surface EGFR through recycling inhibition, while upregulating the activation of several other receptor tyrosine kinases (RTKs) that might promote invasion. In particular, FGF2, likely acting through FGFR1, promoted invasion of C3G-silenced GBM cells. Moreover, ERKs mediate this invasiveness, both in response to FGF2- and serum-induced chemoattraction. In conclusion, our data show the distinct dependency of GBM tumors on C3G for EGF/EGFR signaling versus other RTKs, suggesting that assessing C3G levels may discriminate GBM patient responders to different RTK inhibition protocols. Hence, patients with a low C3G expression might not respond to EGFR inhibitors.This work was supported by grants from the Spanish Ministry of Economy and Competitiveness [SAF2016-76588-C2-1-R and PID2019-104143RB-C22 to AP; and SAF2016-76588-C2-2-R and PID2019-104143RB-C21 to CG], and by two grants from the Council of Education of Junta de Castilla y León, Spain [SA017U16 and SA078P20 to CG]. All funding was cosponsored by the European FEDER Program. SM and OH are recipients of FPU fellowships from Spanish Ministry of Education. CS was supported by a fellowship from Complutense University from Madrid. A G-U and MRF are supported by Madrid Community Program for Talent Attraction (MRF 2017-T1/BMD-5468). P. B. received support from BBVA (Becas Leonardo 2018, BBM-TRA-0041)

Met signaling in cardiomyocytes is required for normal cardiac function in adult mice.

Hepatocyte growth factor (HGF) and its receptor, Met, are key determinants of distinct developmental processes. Although HGF exerts cardio-protective effects in a number of cardiac pathologies, it remains unknown whether HGF/Met signaling is essential for myocardial development and/or physiological function in adulthood. We therefore investigated the requirement of HGF/Met signaling in cardiomyocyte for embryonic and postnatal heart development and function by conditional inactivation of the Met receptor in cardiomyocytes using the Cre-α-MHC mouse line (referred to as α-MHCMet-KO). Although α-MHCMet-KO mice showed normal heart development and were viable and fertile, by 6 months of age, males developed cardiomyocyte hypertrophy, associated with interstitial fibrosis. A significant upregulation in markers of myocardial damage, such as β-MHC and ANF, was also observed. By the age of 9 months, α-MHCMet-KO males displayed systolic cardiac dysfunction. Mechanistically, we provide evidence of a severe imbalance in the antioxidant defenses in α-MHCMet-KO hearts involving a reduced expression and activity of catalase and superoxide dismutase, with consequent reactive oxygen species accumulation. Similar anomalies were observed in females, although with a slower kinetics. We also found that Met signaling down-regulation leads to an increase in TGF-β production and a decrease in p38MAPK activation, which may contribute to phenotypic alterations displayed in α-MHCMet-KO mice. Consistently, we show that HGF acts through p38α to upregulate antioxidant enzymes in cardiomyocytes. Our results highlight that HGF/Met signaling in cardiomyocytes plays a physiological cardio-protective role in adult mice by acting as an endogenous regulator of heart function through oxidative stress control.Comunidad de Madrid/Universidad Complutense de Madrid; Association Française contre les Myopathies; Seventh Framework Programme; Fondation pour la Recherche Médicale; Instituto de Salud Carlos III; Ministerio de Ciencia e Innovación; Fondation Bettencourt Schueller; European Regional Development Fund; Junta de Andalucía; Junta de Castilla y Leó

Uncovering a Novel Functional Interaction Between Adult Hepatic Progenitor Cells, Inflammation and EGFR Signaling During Bile Acids-Induced Injury

Chronic cholestatic damage is associated to both accumulation of cytotoxic levels of bile acids and expansion of adult hepatic progenitor cells (HPC) as part of the ductular reaction contributing to the regenerative response. Here, we report a bile acid-specific cytotoxic response in mouse HPC, which is partially impaired by EGF signaling. Additionally, we show that EGF synergizes with bile acids to trigger inflammatory signaling and NLRP3 inflammasome activation in HPC. Aiming at understanding the impact of this HPC specific response on the liver microenvironment we run a proteomic analysis of HPC secretome. Data show an enrichment in immune and TGF-beta regulators, ECM components and remodeling proteins in HPC secretome. Consistently, HPC-derived conditioned medium promotes hepatic stellate cell (HSC) activation and macrophage M1-like polarization. Strikingly, EGF and bile acids co-treatment leads to profound changes in the secretome composition, illustrated by an abolishment of HSC activating effect and by promoting macrophage M2-like polarization. Collectively, we provide new specific mechanisms behind HPC regulatory action during cholestatic liver injury, with an active role in cellular interactome and inflammatory response regulation. Moreover, findings prove a key contribution for EGFR signaling jointly with bile acids in HPC-mediated actions

In vivo production of fluorine-18 in a chicken egg tumor model of breast cancer for proton therapy range verification

Range verification of clinical protontherapy systems via positron-emission tomography (PET) is not a mature technology, suffering from two major issues: insufficient signal from low-energy protons in the Bragg peak area and biological washout of PET emitters. The use of contrast agents including O-18, Zn-68 or Cu-63, isotopes with a high cross section for low-energy protons in nuclear reactions producing PET emitters, has been proposed to enhance the PET signal in the last millimeters of the proton path. However, it remains a challenge to achieve sufficient concentrations of these isotopes in the target volume. Here we investigate the possibilities of O-18-enriched water (18-W), a potential contrast agent that could be incorporated in large proportions in live tissues by replacing regular water. We hypothesize that 18-W could also mitigate the problem of biological washout, as PET (F-18) isotopes created inside live cells would remain trapped in the form of fluoride anions (F-), allowing its signal to be detected even hours after irradiation. To test our hypothesis, we designed an experiment with two main goals: first, prove that 18-W can incorporate enough O-18 into a living organism to produce a detectable signal from F-18 after proton irradiation, and second, determine the amount of activity that remains trapped inside the cells. The experiment was performed on a chicken embryo chorioallantoic membrane tumor model of head and neck cancer. Seven eggs with visible tumors were infused with 18-W and irradiated with 8-MeV protons (range in water: 0.74 mm), equivalent to clinical protons at the end of particle range. The activity produced after irradiation was detected and quantified in a small-animal PET-CT scanner, and further studied by placing ex-vivo tumours in a gamma radiation detector. In the acquired images, specific activity of F-18 (originating from 18-W) could be detected in the tumour area of the alive chicken embryo up to 9 h after irradiation, which confirms that low-energy protons can indeed produce a detectable PET signal if a suitable contrast agent is employed. Moreover, dynamic PET studies in two of the eggs evidenced a minimal effect of biological washout, with 68% retained specific F-18 activity at 8 h after irradiation. Furthermore, ex-vivo analysis of 4 irradiated tumours showed that up to 3% of oxygen atoms in the targets were replaced by O-18 from infused 18-W, and evidenced an entrapment of 59% for specific activity of F-18 after washing, supporting our hypothesis that F- ions remain trapped within the cells. An infusion of 18-W can incorporate O-18 in animal tissues by replacing regular water inside cells, producing a PET signal when irradiated with low-energy protons that could be used for range verification in protontherapy. F-18 produced inside cells remains entrapped and suffers from minimal biological washout, allowing for a sharper localization with longer PET acquisitions. Further studies must evaluate the feasibility of this technique in dosimetric conditions closer to clinical practice, in order to define potential protocols for its use in patients

Contribution of c3g and other gefs to liver cancer development and progression

© The Author(s) 2021.Primary liver cancers constitute the fourth leading cause of cancer mortality worldwide, due to their high morbidity, late diagnosis and lack of effective treatments. Hepatocellular carcinoma (HCC) represents 80% and cholangiocarcinoma (CCA) 15% of liver cancers. Several genetic and epigenetic gene alterations (e.g., TERT, TP53 or CTNNB1) are HCC drivers, although many additional gene alterations contribute to HCC initiation and/or progression. Rho and Ras GTPases have been widely implicated in tumorigenesis and their activators (GEFs) have recently emerged as putative key players in liver cancer. The Ras GEF, C3G (RAPGEF1), a GEF mainly for Rap proteins, has recently been uncovered as a relevant gene in HCC. Its upregulation promotes tumor growth, although a decrease in C3G levels favors migration/invasion and lung metastasis. Rap1A/1B/2A/2B are overexpressed in HCC tumors, but their effects are controversial and not equivalent to those of C3G. The C3G partner, CRKL, is also overexpressed in HCC, promoting proliferation, migration and invasion. Various Rho GEFs are also deregulated in liver cancer. Tiam1 and Tiam2 expression is upregulated in HCC, promoting proliferation, migration and metastasis. In addition, ARHGEF-10L/9/19/39 are overexpressed in HCC tumors, facilitating migration, invasion, metastasis and proliferation. Another Rho GEF, Vav2, is also involved in metastasis. Little is known about the participation of these GEFs and GTPases in CCA. However, analysis of cancer databases uncovered deregulations or genetic alterations in several of these genes, in both CCA and HCC. Hence, GEFs function appear essential for liver homeostasis, although future studies are needed to define their precise function in liver cancer.The work was supported by grants from the Spanish Ministry of Economy and Competitiveness (SAF2016-76588-C2-1-R and PID2019-104143RB-C22 to Porras A; and SAF2016-76588-C2-2-R and PID2019-104143RB-C21 to Guerrero G and PID2019-104991RB-I00 to Bragado P), and by two grants from the Council of Education of Junta de Castilla y León, Spain (SA017U16 and SA078P20 to Guerrero C). All funding was cosponsored by the European FEDER Program. Sequera C was supported by a fellowship from Complutense University from Madrid. Gutierrez-Uzquiza A is supported by Madrid Community Program for Talent Attraction (MRF 2017-T1/BMD-5468). Bragado P received support from BBVA (Becas Leonardo 2018, BBM-TRA-0041)

C3G down-regulates p38 MAPK activity in response to stress by Rap-1 independent mechanisms: Involvement in cell death

We present here evidences supporting a negative regulation of p38α MAPK activity by C3G in MEFs triggered by stress, which can mediate cell death or survival depending on the stimuli. Upon serum deprivation, C3G induces survival through inhibition of p38α activation, which mediates apoptosis. In contrast, in response to H2O2, C3G behaves as a pro-apoptotic molecule, as its knock-down or knock-out enhances survival through up-regulation of p38α activation, which plays an anti-apoptotic role under these conditions. Moreover, the C3G target, Rap-1, plays an opposite role, also through regulation of p38α MAPK activity. Our data also suggest that changes in the protein levels of some members of the Bcl-2 family could account for the regulation of cell death by C3G and/or Rap-1 through p38α MAPK. Bim/Bcl-xL ratio appears to be important in the regulation of cell survival, both upon serum deprivation and in response to H2O2. In addition, the increase in BNIP-3 levels induced by C3G knock-down in wt cells treated with H2O2 might play a role preventing cell death. Therefore, we can conclude that C3G is a negative regulator of p38α MAPK in MEFs, while Rap-1 is a positive regulator, but both, through the regulation of p38α activity, can promote cell survival or cell death depending on the stimuli. © 2009 Elsevier Inc. All rights reserved.This work was supported by grants FIS-PI041131 and FIS-PI070071 (CG: FISPI041324 and FIS-PI070078) from ISCIII, Ministry of Science and Innovation, Spain; and grants from Comunidad de Madrid/Universidad Complutense de Madrid: CAM/UCM 920384 (CCG07-UCM/SAL-2148), Spain. A.G.-U. is a predoctoral student supported by Comunidad de Madrid, Spain. V.M is a predoctoral student supported by grant FISPI070078.Peer Reviewe

Rac signaling in breast cancer: A tale of GEFs and GAPs

Rac GTPases, small G-proteins widely implicated in tumorigenesis and metastasis, transduce signals from tyrosine-kinase, G-protein-coupled receptors (GPCRs), and integrins, and control a number of essential cellular functions including motility, adhesion, and proliferation. Deregulation of Rac signaling in cancer is generally a consequence of enhanced upstream inputs from tyrosine-kinase receptors, PI3K or Guanine nucleotide Exchange Factors (GEFs), or reduced Rac inactivation by GTPase Activating Proteins (GAPs). In breast cancer cells Rac1 is a downstream effector of ErbB receptors and mediates migratory responses by ErbB1/EGFR ligands such as EGF or TGFα and ErbB3 ligands such as heregulins. Recent advances in the field led to the identification of the Rac-GEF P-Rex1 as an essential mediator of Rac1 responses in breast cancer cells. P-Rex1 is activated by the PI3K product PIP3 and Gβγ subunits, and integrates signals from ErbB receptors and GPCRs. Most notably, P-Rex1 is highly overexpressed in human luminal breast tumors, particularly those expressing ErbB2 and estrogen receptor (ER). The P-Rex1/Rac signaling pathway may represent an attractive target for breast cancer therapy.Susan G. Komen for the Cure (M.G.K.)National Institutes of Health (NIH)Depto. de Bioquímica y Biología MolecularFac. de FarmaciaTRUEpu

p38α Mediates Cell Survival in Response to Oxidative Stress via Induction of Antioxidant Genes

We reveal a novel pro-survival role for mammalian p38α in response to H(2)O(2), which involves an up-regulation of antioxidant defenses. The presence of p38α increases basal and H(2)O(2)-induced expression of the antioxidant enzymes: superoxide-dismutase 1 (SOD-1), SOD-2, and catalase through different mechanisms, which protects from reactive oxygen species (ROS) accumulation and prevents cell death. p38α was found to regulate (i) H(2)O(2)-induced SOD-2 expression through a direct regulation of transcription mediated by activating transcription factor 2 (ATF-2) and (ii) H(2)O(2)-induced catalase expression through regulation of protein stability and mRNA expression and/or stabilization. As a consequence, SOD and catalase activities are higher in WT MEFs. We also found that this p38α-dependent antioxidant response allows WT cells to maintain an efficient activation of the mTOR/p70S6K pathway. Accordingly, the loss of p38α leads to ROS accumulation in response to H(2)O(2), which causes cell death and inactivation of mTOR/p70S6K signaling. This can be rescued by either p38α re-expression or treatment with the antioxidants, N-acetyl cysteine, or exogenously added catalase. Therefore, our results reveal a novel homeostatic role for p38α in response to oxidative stress, where ROS removal is favored by antioxidant enzymes up-regulation, allowing cell survival and mTOR/p70S6K activation.National Institutes of HealthMinistry of Science and Innovation of SpainComunidad de MadridUniversidad Complutense de MadridSamuel Waxman Cancer Research Foundation Tumor DormancyNew York Stem Cell ScienceDepto. de Bioquímica y Biología MolecularFac. de FarmaciaTRUEpu

C3G protein, a new player in glioblastoma

© 2021 by the authors.C3G (RAPGEF1) is a guanine nucleotide exchange factor (GEF) for GTPases from the Ras superfamily, mainly Rap1, although it also acts through GEF-independent mechanisms. C3G regulates several cellular functions. It is expressed at relatively high levels in specific brain areas, playing important roles during embryonic development. Recent studies have uncovered different roles for C3G in cancer that are likely to depend on cell context, tumour type, and stage. However, its role in brain tumours remained unknown until very recently. We found that C3G expression is downregulated in GBM, which promotes the acquisition of a more mesenchymal phenotype, enhancing migration and invasion, but not proliferation. ERKs hyperactivation, likely induced by FGFR1, is responsible for this pro-invasive effect detected in C3G silenced cells. Other RTKs (Receptor Tyrosine Kinases) are also dysregulated and could also contribute to C3G effects. However, it remains undetermined whether Rap1 is a mediator of C3G actions in GBM. Various Rap1 isoforms can promote proliferation and invasion in GBM cells, while C3G inhibits migration/invasion. Therefore, other RapGEFs could play a major role regulating Rap1 activity in these tumours. Based on the information available, C3G could represent a new biomarker for GBM diagnosis, prognosis, and personalised treatment of patients in combination with other GBM molecular markers. The quantification of C3G levels in circulating tumour cells (CTCs) in the cerebrospinal liquid and/or circulating fluids might be a useful tool to improve GBM patient treatment and survival.This work was supported by grants from the Spanish Ministry of Economy and Competitiveness [SAF2016-76588-C2-1-R and PID2019-104143RB-C22 to A.P.; SAF2016-76588-C2-2-R and PID2019-104143RB-C21 to C.G. and PID2019-104991RB-I00 to P.B.], and by two grants from the Council of Education of Junta de Castilla y León, Spain [SA017U16 and SA078P20 to C.G.]. All funding was cosponsored by the European FEDER Programme. S.M. was a recipient of a FPU fellowship from Spanish Ministry of Education. A.G.-U. is supported by Madrid Community Programme for Talent Attraction (2017-T1/BMD-5468)