Curcumin restrains hepatic glucose production by blocking cAMP/PKA signaling and reducing acetyl CoA accumulation in high-fat diet (HFD)-fed mice

Publication date: Available online 27 February 2018
Source:Molecular and Cellular Endocrinology
Author(s): Zixia Wang, Dan Xu, Linlin She, Yirui Zhang, Qingli Wei, Jiye Aa, Guangji Wang, Baolin Liu, Yuan Xie
ObjectiveThis study is designed to investigate whether curcumin reduces excessive hepatic glucose production (HGP) via regulation of second messenger cAMP.MethodsHigh-fat diet (HFD)-fed mice were orally administrated of metformin (200 mg/kg) or curcumin (50 mg/kg) daily for 10 weeks. Meanwhile, we stimulated mouse primary hepatocytes with palmitate (PA).ResultsCurcumin reduced hepatic cAMP accumulation by preserving PDE4B induction, thereby suppressing gluconeogenesis via blocking cAMP/PKA activation. Curcumin reduced lipid deposition by reducing free fatty acid uptake and prevented acetyl CoA accumulation by combating mitochondrial oxidation. As a result from inhibiting acetyl CoA accumulation, curcumin protected pyruvate dehydrogenase (PDH) activity and inhibited pyruvate carboxylase (PC), limiting the shift of mitochondrial pyruvate from oxidation to gluconeogenesis via the carboxylation.ConclusionCurcumin reduced cAMP accumulation by preserving PDE4B activity and inhibited acetyl CoA production by reducing mitochondrial fatty acid oxidation, thereby restraining pyruvate-driven hepatic glucose production.



http://ift.tt/2CMaxX6

Resistance to BET Inhibitor Leads to Alternative Therapeutic Vulnerabilities in Castration-Resistant Prostate Cancer

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Aishwarya Pawar, Paradesi Naidu Gollavilli, Shaomeng Wang, Irfan A. Asangani
BRD4 plays a major role in the transcription networks orchestrated by androgen receptor (AR) in castration-resistant prostate cancer (CRPC). Several BET inhibitors (BETi) that displace BRD4 from chromatin are being evaluated in clinical trials for CRPC. Here, we describe mechanisms of acquired resistance to BETi that are amenable to targeted therapies in CRPC. BETi-resistant CRPC cells displayed cross-resistance to a variety of BETi in the absence of gatekeeper mutations, exhibited reduced chromatin-bound BRD4, and were less sensitive to BRD4 degraders/knockdown, suggesting a BRD4-independent transcription program. Transcriptomic analysis revealed reactivation of AR signaling due to CDK9-mediated phosphorylation of AR, resulting in sensitivity to CDK9 inhibitors and enzalutamide. Additionally, increased DNA damage associated with PRC2-mediated transcriptional silencing of DDR genes was observed, leading to PARP inhibitor sensitivity. Collectively, our results identify the therapeutic limitation of BETi as a monotherapy; however, our BETi resistance data suggest unique opportunities for combination therapies in treating CRPC.

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Teaser

Resistance to targeted therapies is a major problem. Pawar et al. investigate the potential mechanisms of acquired resistance to BET inhibitors in prostate cancer and identify actionable targets to overcome the resistance. This study highlights the therapeutic limitation of BET inhibitors as a monotherapy and suggests potential combination therapies in treating prostate cancer.


http://ift.tt/2GMIqJO

SynDIG4/Prrt1 Is Required for Excitatory Synapse Development and Plasticity Underlying Cognitive Function

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Lucas Matt, Lyndsey M. Kirk, George Chenaux, David J. Speca, Kyle R. Puhger, Michael C. Pride, Mohammad Qneibi, Tomer Haham, Kristopher E. Plambeck, Yael Stern-Bach, Jill L. Silverman, Jacqueline N. Crawley, Johannes W. Hell, Elva Díaz
Altering AMPA receptor (AMPAR) content at synapses is a key mechanism underlying the regulation of synaptic strength during learning and memory. Previous work demonstrated that SynDIG1 (synapse differentiation-induced gene 1) encodes a transmembrane AMPAR-associated protein that regulates excitatory synapse strength and number. Here we show that the related protein SynDIG4 (also known as Prrt1) modifies AMPAR gating properties in a subunit-dependent manner. Young SynDIG4 knockout (KO) mice have weaker excitatory synapses, as evaluated by immunocytochemistry and electrophysiology. Adult SynDIG4 KO mice show complete loss of tetanus-induced long-term potentiation (LTP), while mEPSC amplitude is reduced by only 25%. Furthermore, SynDIG4 KO mice exhibit deficits in two independent cognitive assays. Given that SynDIG4 colocalizes with the AMPAR subunit GluA1 at non-synaptic sites, we propose that SynDIG4 maintains a pool of extrasynaptic AMPARs necessary for synapse development and function underlying higher-order cognitive plasticity.

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Teaser

Matt et al. show that mice lacking the AMPAR-associated protein SynDIG4/Prrt1 display deficits in synaptic plasticity and cognition. SynDIG4 modifies AMPAR biophysical properties in heterologous cells, but synaptic AMPAR kinetics are unchanged, suggesting that SynDIG4 establishes a pool of extrasynaptic AMPARs necessary for higher-order cognitive plasticity.


http://ift.tt/2HQztk3

A NuRD Complex from Xenopus laevis Eggs Is Essential for DNA Replication during Early Embryogenesis

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Christo P. Christov, Kevin S. Dingwell, Mark Skehel, Helen S. Wilkes, Julian E. Sale, James C. Smith, Torsten Krude
DNA replication in the embryo of Xenopus laevis changes dramatically at the mid-blastula transition (MBT), with Y RNA-independent random initiation switching to Y RNA-dependent initiation at specific origins. Here, we identify xNuRD, an MTA2-containing assemblage of the nucleosome remodeling and histone deacetylation complex NuRD, as an essential factor in pre-MBT Xenopus embryos that overcomes a functional requirement for Y RNAs during DNA replication. Human NuRD complexes have a different subunit composition than xNuRD and do not support Y RNA-independent initiation of DNA replication. Blocking or immunodepletion of xNuRD inhibits DNA replication initiation in isolated nuclei in vitro and causes inhibition of DNA synthesis, developmental delay, and embryonic lethality in early embryos. xNuRD activity declines after the MBT, coinciding with dissociation of the complex and emergence of Y RNA-dependent initiation. Our data thus reveal an essential role for a NuRD complex as a DNA replication factor during early Xenopus development.

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Teaser

Christov et al. show that the chromatin remodeling complex xNuRD is an essential DNA replication factor in the eggs and early embryos of Xenopus laevis. They demonstrate that xNuRD can initiate DNA replication in the absence of non-coding Y RNAs, which only become essential for replication later in development.


http://ift.tt/2GMIpFK

Nap1l1 Controls Embryonic Neural Progenitor Cell Proliferation and Differentiation in the Developing Brain

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Huimin Qiao, Yanxin Li, Chao Feng, Shuguang Duo, Fen Ji, Jianwei Jiao
The precise function and role of nucleosome assembly protein 1-like 1 (Nap1l1) in brain development are unclear. Here, we find that Nap1l1 knockdown decreases neural progenitor cell (NPC) proliferation and induces premature neuronal differentiation during cortical development. A similar deficiency in embryonic neurogenesis was observed in Nap1l1 knockout (KO) mice, which were generated using the CRISPR-Cas9 system. RNA sequencing (RNA-seq) analysis indicates that Ras-associated domain family member 10 (RassF10) may be the downstream target of Nap1l1. Furthermore, we found that Nap1l1 regulates RassF10 expression by promoting SETD1A-mediated H3K4 trimethylation at the RassF10 promoter. Nap1l1 KO defects may be rescued by RassF10 overexpression, suggesting that Nap1l1 controls NPC differentiation through RassF10. Our findings reveal an essential role for the Nap1l1 histone chaperone in cortical neurogenesis during early embryonic brain development.

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Teaser

Nap1l1 plays essential roles in embryonic neurogenesis, including the proliferation and differentiation of neural progenitors. Qiao et al. find that Nap1l1 regulates RassF10 through SETD1A-mediated H3K4me3 of the RassF10 promoter.


http://ift.tt/2HNwQzg

A Single Administration of CRISPR/Cas9 Lipid Nanoparticles Achieves Robust and Persistent In Vivo Genome Editing

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Jonathan D. Finn, Amy Rhoden Smith, Mihir C. Patel, Lucinda Shaw, Madeleine R. Youniss, Jane van Heteren, Tanner Dirstine, Corey Ciullo, Reynald Lescarbeau, Jessica Seitzer, Ruchi R. Shah, Aalok Shah, Dandan Ling, Jacqueline Growe, Melissa Pink, Ellen Rohde, Kristy M. Wood, William E. Salomon, William F. Harrington, Christian Dombrowski, Walter R. Strapps, Yong Chang, David V. Morrissey
The development of clinically viable delivery methods presents one of the greatest challenges in the therapeutic application of CRISPR/Cas9 mediated genome editing. Here, we report the development of a lipid nanoparticle (LNP)-mediated delivery system that, with a single administration, enabled significant editing of the mouse transthyretin (Ttr) gene in the liver, with a >97% reduction in serum protein levels that persisted for at least 12 months. These results were achieved with an LNP delivery system that was biodegradable and well tolerated. The LNP delivery system was combined with a sgRNA having a chemical modification pattern that was important for high levels of in vivo activity. The formulation was similarly effective in a rat model. Our work demonstrates that this LNP system can deliver CRISPR/Cas9 components to achieve clinically relevant levels of in vivo genome editing with a concomitant reduction of TTR serum protein, highlighting the potential of this system as an effective genome editing platform.

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Teaser

Finn et al. describe the development of a transient, biodegradable LNP-based CRISPR/Cas9 delivery system that achieves >97% knockdown of serum TTR levels following a single administration. Editing levels were stable for 12 months, despite the transient nature of the delivery system and the editing components.


http://ift.tt/2HQ8l4x

Ubiquitination of MBNL1 Is Required for Its Cytoplasmic Localization and Function in Promoting Neurite Outgrowth

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Pei-Ying Wang, Kuei-Ting Chang, Yu-Mei Lin, Ting-Yu Kuo, Guey-Shin Wang
The Muscleblind-like protein family (MBNL) plays an important role in regulating the transition between differentiation and pluripotency and in the pathogenesis of myotonic dystrophy type 1 (DM1), a CTG expansion disorder. How different MBNL isoforms contribute to the differentiation and are affected in DM1 has not been investigated. Here, we show that the MBNL1 cytoplasmic, but not nuclear, isoform promotes neurite morphogenesis and reverses the morphological defects caused by expanded CUG RNA. Cytoplasmic MBNL1 is polyubiquitinated by lysine 63 (K63). Reduced cytoplasmic MBNL1 in the DM1 mouse brain is consistent with the reduced extent of K63 ubiquitination. Expanded CUG RNA induced the deubiqutination of cytoplasmic MBNL1, which resulted in nuclear translocation and morphological impairment that could be ameliorated by inhibiting K63-linked polyubiquitin chain degradation. Our results suggest that K63-linked ubiquitination of MBNL1 is required for its cytoplasmic localization and that deubiquitination of cytoplasmic MBNL1 is pathogenic in the DM1 brain.

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Teaser

Wang et al. find that MBNL1 ubiquitination is required for cytoplasmic localization and promotion of neurite outgrowth. In myotonic dystrophy, expanded CUG repeat RNA leads to MBNL1 deubiquitination, resulting in nuclear-translocation-associated morphological defects that can be rescued by preventing degradation of lysine 63-linked polyubiquitin chains or enhancing MBNL1 ubiquitination.


http://ift.tt/2GMIoBG

The α2δ-1-NMDA Receptor Complex Is Critically Involved in Neuropathic Pain Development and Gabapentin Therapeutic Actions

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Jinjun Chen, Lingyong Li, Shao-Rui Chen, Hong Chen, Jing-Dun Xie, Rita E. Sirrieh, David M. MacLean, Yuhao Zhang, Meng-Hua Zhou, Vasanthi Jayaraman, Hui-Lin Pan
α2δ-1, commonly known as a voltage-activated Ca²⁺ channel subunit, is a binding site of gabapentinoids used to treat neuropathic pain and epilepsy. However, it is unclear how α2δ-1 contributes to neuropathic pain and gabapentinoid actions. Here, we show that Cacna2d1 overexpression potentiates presynaptic and postsynaptic NMDAR activity of spinal dorsal horn neurons to cause pain hypersensitivity. Conversely, Cacna2d1 knockdown or ablation normalizes synaptic NMDAR activity increased by nerve injury. α2δ-1 forms a heteromeric complex with NMDARs in rodent and human spinal cords. The α2δ-1-NMDAR interaction predominantly occurs through the C terminus of α2δ-1 and promotes surface trafficking and synaptic targeting of NMDARs. Gabapentin or an α2δ-1 C terminus-interfering peptide normalizes NMDAR synaptic targeting and activity increased by nerve injury. Thus, α2δ-1 is an NMDAR-interacting protein that increases NMDAR synaptic delivery in neuropathic pain. Gabapentinoids reduce neuropathic pain by inhibiting forward trafficking of α2δ-1-NMDAR complexes.

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Teaser

Chen et al. show that α2δ-1, through its C terminus, physically interacts with NMDA receptors and promotes synaptic expression of α2δ-1-NMDA receptor complexes in neuropathic pain. Gabapentin reduces neuropathic pain primarily by targeting α2δ-1-bound NMDA receptors.


http://ift.tt/2HQEedb

Spontaneous Vesicle Fusion Is Differentially Regulated at Cholinergic and GABAergic Synapses

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Haowen Liu, Lei Li, Wei Wang, Jihong Gong, Xiaofei Yang, Zhitao Hu
The locomotion of C. elegans is balanced by excitatory and inhibitory neurotransmitter release at neuromuscular junctions. However, the molecular mechanisms that maintain the balance of synaptic transmission remain enigmatic. Here, we investigated the function of voltage-gated Ca²⁺ channels in triggering spontaneous release at cholinergic and GABAergic synapses. Recordings of the miniature excitatory/inhibitory postsynaptic currents (mEPSCs and mIPSCs, respectively) showed that UNC-2/CaV2 and EGL-19/CaV1 channels are the two major triggers for spontaneous release. Notably, however, Ca²⁺-independent spontaneous release was observed at GABAergic but not cholinergic synapses. Functional screening led to the identification of hypomorphic unc-64/Syntaxin-1A and snb-1/VAMP2 mutants in which mEPSCs are severely impaired, whereas mIPSCs remain unaltered, indicating differential regulation of these currents at cholinergic and GABAergic synapses. Moreover, Ca²⁺-independent spontaneous GABA release was nearly abolished in the hypomorphic unc-64 and snb-1 mutants, suggesting distinct mechanisms for Ca²⁺-dependent and Ca²⁺-independent spontaneous release.

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Teaser

Liu et al. show that spontaneous release is differentially regulated between cholinergic and GABAergic synapses at the C. elegans NMJ. Ca²⁺-independent spontaneous release is observed in GABAergic synapses and regulated by synaptic proteins such as syntaxin-1A and VAMP2.


http://ift.tt/2HPPo1W

Two Parallel Pathways Assign Opposing Odor Valences during Drosophila Memory Formation

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Daisuke Yamazaki, Makoto Hiroi, Takashi Abe, Kazumichi Shimizu, Maki Minami-Ohtsubo, Yuko Maeyama, Junjiro Horiuchi, Tetsuya Tabata
During olfactory associative learning in Drosophila, odors activate specific subsets of intrinsic mushroom body (MB) neurons. Coincident exposure to either rewards or punishments is thought to activate extrinsic dopaminergic neurons, which modulate synaptic connections between odor-encoding MB neurons and MB output neurons to alter behaviors. However, here we identify two classes of intrinsic MB γ neurons based on cAMP response element (CRE)-dependent expression, γCRE-p and γCRE-n, which encode aversive and appetitive valences. γCRE-p and γCRE-n neurons act antagonistically to maintain neutral valences for neutral odors. Activation or inhibition of either cell type upsets this balance, toggling odor preferences to either positive or negative values. The mushroom body output neurons, MBON-γ5β′2a/β′2mp and MBON-γ2α′1, mediate the actions of γCRE-p and γCRE-n neurons. Our data indicate that MB neurons encode valence information, as well as odor information, and this information is integrated through a process involving MBONs to regulate learning and memory.

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Teaser

Aversive and appetitive olfactory memories in fruit flies are formed in third order olfactory neurons, the mushroom body Kenyon cells (KCs). Yamazaki et al. identify parallel pathways consisting of two subpopulations of KCs and their output neurons that encode aversive and appetitive valences.


http://ift.tt/2GMInO8

A Drosophila Model of Intellectual Disability Caused by Mutations in the Histone Demethylase KDM5

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Sumaira Zamurrad, Hayden A.M. Hatch, Coralie Drelon, Helen M. Belalcazar, Julie Secombe
Mutations in KDM5 family histone demethylases cause intellectual disability in humans. However, the molecular mechanisms linking KDM5-regulated transcription and cognition remain unknown. Here, we establish Drosophila as a model to understand this connection by generating a fly strain harboring an allele analogous to a disease-causing missense mutation in human KDM5C (kdm5^A512P). Transcriptome analysis of kdm5^A512P flies revealed a striking downregulation of genes required for ribosomal assembly and function and a concomitant reduction in translation. kdm5^A512P flies also showed impaired learning and/or memory. Significantly, the behavioral and transcriptional changes in kdm5^A512P flies were similar to those specifically lacking demethylase activity. These data suggest that the primary defect of the KDM5^A512P mutation is a loss of histone demethylase activity and reveal an unexpected role for this enzymatic function in gene activation. Because translation is critical for neuronal function, we propose that this defect contributes to the cognitive defects of kdm5^A512P flies.

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Teaser

In humans, mutations in the transcriptional regulator KDM5 result in intellectual disability (ID). Here, Zamurrad et al. generate a Drosophila strain harboring a KDM5 mutation equivalent to an ID-associated allele to reveal a conserved role for KDM5 in cognition and an unexpected role for KDM5's enzymatic activity in gene activation.


http://ift.tt/2HQ8ftH

Action Selection and Flexible Switching Controlled by the Intralaminar Thalamic Neurons

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Shigeki Kato, Ryoji Fukabori, Kayo Nishizawa, Kana Okada, Nozomu Yoshioka, Masateru Sugawara, Yuko Maejima, Kenju Shimomura, Masahiro Okamoto, Satoshi Eifuku, Kazuto Kobayashi
Learning processes contributing to appropriate selection and flexible switching of behaviors are mediated through the dorsal striatum, a key structure of the basal ganglia circuit. The major inputs to striatal subdivisions are provided from the intralaminar thalamic nuclei, including the central lateral nucleus (CL) and parafascicular nucleus (PF). Thalamostriatal neurons in the PF modulate the acquisition and performance of stimulus-response learning. Here, we address the roles of the CL thalamostriatal neurons in learning processes by using a selective neural pathway targeting technique. We show that the CL neurons are essential for the performance of stimulus-response learning and for behavioral flexibility, including reversal and attentional set-shifting of learned responses. In addition, chemogenetic suppression of neural activity supports the requirements of these neurons for behavioral flexibility. Our results suggest that the main contribution of the CL thalamostriatal neurons is functional control of the basal ganglia circuit linked to the prefrontal cortex.

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Teaser

Intralaminar thalamic nuclei provide the major inputs to the cortico-basal ganglia circuit. Kato et al. describe the essential roles of the thalamostriatal neurons in the CL in the performance of stimulus-response learning and in reversal and set-shifting of learned behaviors, forming a pivotal route that affects the frontostriatal circuit functions.


http://ift.tt/2GMImK4

Oligodendrocytes in the Mouse Corpus Callosum Maintain Axonal Function by Delivery of Glucose

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Niklas Meyer, Nadine Richter, Zoya Fan, Gabrielle Siemonsmeier, Tatyana Pivneva, Philipp Jordan, Christian Steinhäuser, Marcus Semtner, Christiane Nolte, Helmut Kettenmann
In the optic nerve, oligodendrocytes maintain axonal function by supplying lactate as an energy substrate. Here, we report that, in acute brain slices of the mouse corpus callosum, exogenous glucose deprivation (EGD) abolished compound action potentials (CAPs), which neither lactate nor pyruvate could prevent. Loading an oligodendrocyte with 20 mM glucose using a patch pipette prevented EGD-mediated CAP reduction in about 70% of experiments. Loading oligodendrocytes with lactate rescued CAPs less efficiently than glucose. In mice lacking connexin 47, oligodendrocyte filling with glucose did not prevent CAP loss, emphasizing the importance of glial networks for axonal energy supply. Compared with the optic nerve, the astrocyte network in the corpus callosum was less dense, and loading astrocytes with glucose did not prevent CAP loss during EGD. We suggest that callosal oligodendrocyte networks provide energy to sustain axonal function predominantly by glucose delivery, and mechanisms of metabolic support vary across different white matter regions.

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Teaser

Meyer et al. find that, unlike in the optic nerve, lactate does not substitute for glucose to sustain axonal function in the mouse corpus callosum. Oligodendrocyte networks in the corpus callosum provide energy substrates to axons predominantly by delivery of glucose, indicating different metabolic support mechanisms among white matter regions.


http://ift.tt/2HOSpPU

Aspirin Recapitulates Features of Caloric Restriction

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Federico Pietrocola, Francesca Castoldi, Maria Markaki, Sylvie Lachkar, Guo Chen, David P. Enot, Sylvere Durand, Noelie Bossut, Mingming Tong, Shoaib A. Malik, Friedemann Loos, Nicolas Dupont, Guillermo Mariño, Nejma Abdelkader, Frank Madeo, Maria Chiara Maiuri, Romano Kroemer, Patrice Codogno, Junichi Sadoshima, Nektarios Tavernarakis, Guido Kroemer
The age-associated deterioration in cellular and organismal functions associates with dysregulation of nutrient-sensing pathways and disabled autophagy. The reactivation of autophagic flux may prevent or ameliorate age-related metabolic dysfunctions. Non-toxic compounds endowed with the capacity to reduce the overall levels of protein acetylation and to induce autophagy have been categorized as caloric restriction mimetics (CRMs). Here, we show that aspirin or its active metabolite salicylate induce autophagy by virtue of their capacity to inhibit the acetyltransferase activity of EP300. While salicylate readily stimulates autophagic flux in control cells, it fails to further increase autophagy levels in EP300-deficient cells, as well as in cells in which endogenous EP300 has been replaced by salicylate-resistant EP300 mutants. Accordingly, the pro-autophagic activity of aspirin and salicylate on the nematode Caenorhabditis elegans is lost when the expression of the EP300 ortholog cpb-1 is reduced. Altogether, these findings identify aspirin as an evolutionary conserved CRM.

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Teaser

Pietrocola et al. show that the inhibition of the acetyltransferase EP300 is determinant for the autophagy-inducing effect of aspirin and its active metabolite salicylate. As a proof of the evolutionarily conserved nature of this mechanism, the authors demonstrate that aspirin triggers protective autophagy in mice and in the nematode C. elegans.


http://ift.tt/2GObVe1

P2RY1/ALK3-Expressing Cells within the Adult Human Exocrine Pancreas Are BMP-7 Expandable and Exhibit Progenitor-like Characteristics

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Mirza Muhammad Fahd Qadir, Silvia Álvarez-Cubela, Dagmar Klein, Giacomo Lanzoni, Carlos García-Santana, Abelardo Montalvo, Fabiola Pláceres-Uray, Emilia Maria Cristina Mazza, Camillo Ricordi, Luca Alessandro Inverardi, Ricardo Luis Pastori, Juan Domínguez-Bendala
Treatment of human pancreatic non-endocrine tissue with Bone Morphogenetic Protein 7 (BMP-7) leads to the formation of glucose-responsive β-like cells. Here, we show that BMP-7 acts on extrainsular cells expressing PDX1 and the BMP receptor activin-like kinase 3 (ALK3/BMPR1A). In vitro lineage tracing indicates that ALK3⁺ cell populations are multipotent. PDX1⁺/ALK3⁺ cells are absent from islets but prominently represented in the major pancreatic ducts and pancreatic duct glands. We identified the purinergic receptor P2Y1 (P2RY1) as a surrogate surface marker for PDX1. Sorted P2RY1⁺/ALK3^bright+ cells form BMP-7-expandable colonies characterized by NKX6.1 and PDX1 expression. Unlike the negative fraction controls, these colonies can be differentiated into multiple pancreatic lineages upon BMP-7 withdrawal. RNA-seq further corroborates the progenitor-like nature of P2RY1⁺/ALK3^bright+ cells and their multilineage differentiation potential. Our studies confirm the existence of progenitor cells in the adult human pancreas and suggest a specific anatomical location within the ductal and glandular networks.

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Teaser

Qadir et al. describe and characterize a population of multipotent, BMP-7-responsive progenitor-like cells within the human exocrine pancreas. These cells are characterized by the expression of PDX1 and ALK3, a canonical BMP receptor. Their findings shed new light on potential regenerative pathways in the human pancreas.


http://ift.tt/2HQzt3x

Quantitative Operating Principles of Yeast Metabolism during Adaptation to Heat Stress

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Tania Pereira, Ester Vilaprinyo, Gemma Belli, Enric Herrero, Baldiri Salvado, Albert Sorribas, Gisela Altés, Rui Alves
Microorganisms evolved adaptive responses to survive stressful challenges in ever-changing environments. Understanding the relationships between the physiological/metabolic adjustments allowing cellular stress adaptation and gene expression changes being used by organisms to achieve such adjustments may significantly impact our ability to understand and/or guide evolution. Here, we studied those relationships during adaptation to various stress challenges in Saccharomyces cerevisiae, focusing on heat stress responses. We combined dozens of independent experiments measuring whole-genome gene expression changes during stress responses with a simplified kinetic model of central metabolism. We identified alternative quantitative ranges for a set of physiological variables in the model (production of ATP, trehalose, NADH, etc.) that are specific for adaptation to either heat stress or desiccation/rehydration. Our approach is scalable to other adaptive responses and could assist in developing biotechnological applications to manipulate cells for medical, biotechnological, or synthetic biology purposes.

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Teaser

Evolution selects coordinated adaptive changes in gene expression and metabolism that ensure survival to stress challenges. Pereira et al. identify quantitative ranges for those changes in a set of genes and physiological variables (production of ATP, trehalose, NADH, etc.) that are specific for adaptation to heat stress, desiccation/rehydration, or pH.


http://ift.tt/2GOPPrW

S. aureus Evades Macrophage Killing through NLRP3-Dependent Effects on Mitochondrial Trafficking

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Taylor S. Cohen, Michelle L. Boland, Brandon B. Boland, Virginia Takahashi, Andrey Tovchigrechko, Young Lee, Aimee D. Wilde, Mark J. Mazaitis, Omari Jones-Nelson, Christine Tkaczyk, Rajiv Raja, C. Kendall Stover, Bret R. Sellman
Clinical severity of Staphylococcus aureus respiratory infection correlates with alpha toxin (AT) expression. AT activates the NLRP3 inflammasome; deletion of Nlrp3, or AT neutralization, protects mice from lethal S. aureus pneumonia. We tested the hypothesis that this protection is not due to a reduction in inflammasome-dependent cytokines (IL-1β/IL-18) but increased bactericidal function of macrophages. In vivo, neutralization of AT or NLRP3 improved bacterial clearance and survival, while blocking IL-1β/IL-18 did not. Primary human monocytes were used in vitro to determine the mechanism through which NLRP3 alters bacterial killing. In cells treated with small interfering RNA (siRNA) targeting NLRP3 or infected with AT-null S. aureus, mitochondria co-localize with bacterial-containing phagosomes. Mitochondrial engagement activates caspase-1, a process dependent on complex II of the electron transport chain, near the phagosome, promoting its acidification. These data demonstrate a mechanism utilized by S. aureus to sequester itself from antimicrobial processes within the cell.

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Teaser

In the lung, alpha toxin (AT) is a primary virulence factor used by S. aureus to evade innate immune responses. Cohen et al. demonstrate that AT activation of the NLRP3 inflammasome uncouples key components of the phagocytic killing machinery, namely, mitochondria dissociate from internalized bacteria. Without close association of mitochondria with internalized bacteria, macrophages are unable to effectively kill S. aureus.


http://ift.tt/2HPH5TJ

USP2a Supports Metastasis by Tuning TGF-β Signaling

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Yin Zhao, Xiaomeng Wang, Qingqing Wang, Yu Deng, Kang Li, Man Zhang, Qiang Zhang, Jin Zhou, Hong-Yan Wang, Peng Bai, Yujie Ren, Ni Zhang, Weina Li, Yongbo Cheng, Wuhan Xiao, Hai-Ning Du, Xiaoliang Cheng, Lei Yin, Xiangning Fu, Dandan Lin, Qianghui Zhou, Bo Zhong
TGF-β has been demonstrated to promote tumor metastasis, and the regulatory mechanisms are poorly understood. Here, we report the role of USP2a in promoting metastasis by facilitating TGF-β-triggered signaling. USP2a interacts with TGFBR1 and TGFBR2 upon TGF-β stimulation and removes K33-linked polyubiquitin chains from Lys502 of TGFBR1, promoting the recruitment of SMAD2/3. Simultaneously, TGFBR2 phosphorylates Ser207/Ser225 of USP2a, leading to the disassociation of SMAD2/3 from TGFBR1. The phosphorylation of USP2a and SMAD2 is positively correlated in human tumor biopsies, and USP2a is hyper-phosphorylated in lung adenocarcinomas with lymph node invasion. Depletion or pharmacologic inhibition of USP2a dampens TGF-β-triggered signaling and metastasis. Our findings have characterized an essential role of USP2a as a potential target for treatment of metastatic cancers.

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Teaser

Zhao et al. find that USP2a deconjugates K33-linked ubiquitination of TGFBR1 at Lys502 and is phosphorylated at Ser207/Ser225 by TGFBR2 after TGF-β stimulation. This allows R-SMAD recruitment to and subsequent disassociation from the TGFBR1/2 receptor complex.


http://ift.tt/2GOgjd2

GNA11 Q209L Mouse Model Reveals RasGRP3 as an Essential Signaling Node in Uveal Melanoma

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Amanda R. Moore, Leili Ran, Youxin Guan, Jessica J. Sher, Tyler D. Hitchman, Jenny Q. Zhang, Catalina Hwang, Edward G. Walzak, Alexander N. Shoushtari, Sébastien Monette, Rajmohan Murali, Thomas Wiesner, Klaus G. Griewank, Ping Chi, Yu Chen
Uveal melanoma (UM) is characterized by mutually exclusive activating mutations in GNAQ, GNA11, CYSLTR2, and PLCB4, four genes in a linear pathway to activation of PLCβ in almost all tumors and loss of BAP1 in the aggressive subset. We generated mice with melanocyte-specific expression of GNA11^Q209L with and without homozygous Bap1 loss. The GNA11^Q209L mice recapitulated human Gq-associated melanomas, and they developed pigmented neoplastic lesions from melanocytes of the skin and non-cutaneous organs, including the eye and leptomeninges, as well as at atypical sites, including the lymph nodes and lungs. The addition of Bap1 loss increased tumor proliferation and cutaneous melanoma size. Integrative transcriptome analysis of human and murine melanomas identified RasGRP3 to be specifically expressed in GNAQ/GNA11-driven melanomas. In human UM cell lines and murine models, RasGRP3 is specifically required for GNAQ/GNA11-driven Ras activation and tumorigenesis. This implicates RasGRP3 as a critical node and a potential target in UM.

Graphical abstract

Teaser

Moore et al. generate a preclinical mouse model of melanoma that recapitulates features of aggressive uveal melanoma. By comparing murine and human melanomas, they identify a dependency on RasGRP3 in uveal melanoma.


http://ift.tt/2HQ8aWV

PHLDA1 Mediates Drug Resistance in Receptor Tyrosine Kinase-Driven Cancer

Publication date: 27 February 2018
Source:Cell Reports, Volume 22, Issue 9
Author(s): Abbie E. Fearon, Edward P. Carter, Natasha S. Clayton, Edmund H. Wilkes, Ann-Marie Baker, Ekaterina Kapitonova, Bakhouche A. Bakhouche, Yasmine Tanner, Jun Wang, Emanuela Gadaleta, Claude Chelala, Kate M. Moore, John F. Marshall, Juliette Chupin, Peter Schmid, J. Louise Jones, Michelle Lockley, Pedro R. Cutillas, Richard P. Grose
Development of resistance causes failure of drugs targeting receptor tyrosine kinase (RTK) networks and represents a critical challenge for precision medicine. Here, we show that PHLDA1 downregulation is critical to acquisition and maintenance of drug resistance in RTK-driven cancer. Using fibroblast growth factor receptor (FGFR) inhibition in endometrial cancer cells, we identify an Akt-driven compensatory mechanism underpinned by downregulation of PHLDA1. We demonstrate broad clinical relevance of our findings, showing that PHLDA1 downregulation also occurs in response to RTK-targeted therapy in breast and renal cancer patients, as well as following trastuzumab treatment in HER2⁺ breast cancer cells. Crucially, knockdown of PHLDA1 alone was sufficient to confer de novo resistance to RTK inhibitors and induction of PHLDA1 expression re-sensitized drug-resistant cancer cells to targeted therapies, identifying PHLDA1 as a biomarker for drug response and highlighting the potential of PHLDA1 reactivation as a means of circumventing drug resistance.

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Teaser

Fearon et al. use unbiased transcriptomic and phosphoproteomic analysis to identify PHLDA1 as a mediator of acquired resistance to kinase-targeted therapies in cancer. Using a range of cell models and clinical data, they uncover a mechanism underpinning the re-wiring of Akt signaling in cancer drug resistance.


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