HDAC4 integrates PTH and sympathetic signaling in osteoblasts

Parathyroid hormone (PTH) and the sympathetic tone promote Rankl expression in osteoblasts and osteoclast differentiation by enhancing cyclic adenosine monophosphate production through an unidentified transcription factor for PTH and through ATF4 for the sympathetic tone. How two extracellular cues using the same second messenger in the same cell elicit different transcriptional events is unknown. In this paper, we show that PTH favors Rankl expression by triggering the ubiquitination of HDAC4, a class II histone deacetylase, via Smurf2. HDAC4 degradation releases MEF2c, which transactivates the Rankl promoter. Conversely, sympathetic signaling in osteoblasts favors the accumulation of HDAC4 in the nucleus and its association with ATF4. In this context, HDAC4 increases Rankl expression. Because of its ability to differentially connect two extracellular cues to the genome of osteoblasts, HDAC4 is a critical regulator of osteoclast differentiation

Gpr158 mediates osteocalcin's regulation of cognition

That osteocalcin (OCN) is necessary for hippocampal-dependent memory and to prevent anxiety-like behaviors raises novel questions. One question is to determine whether OCN is also sufficient to improve these behaviors in wild-type mice, when circulating levels of OCN decline as they do with age. Here we show that the presence of OCN is necessary for the beneficial influence of plasma from young mice when injected into older mice on memory and that peripheral delivery of OCN is sufficient to improve memory and decrease anxiety-like behaviors in 16-mo-old mice. A second question is to identify a receptor transducing OCN signal in neurons. Genetic, electrophysiological, molecular, and behavioral assays identify Gpr158, an orphan G protein-coupled receptor expressed in neurons of the CA3 region of the hippocampus, as transducing OCN's regulation of hippocampal-dependent memory in part through inositol 1,4,5-trisphosphate and brain-derived neurotrophic factor. These results indicate that exogenous OCN can improve hippocampal-dependent memory in mice and identify molecular tools to harness this pathway for therapeutic purposes

Hypothalamic pregnenolone mediates recognition memory in the context of metabolic disorders

Obesity and type 2 diabetes are associated with cognitive dysfunction. Because the hypothalamus is implicated in energy balance control and memory disorders, we hypothesized that specific neurons in this brain region are at the interface of metabolism and cognition. Acute obesogenic diet administration in mice impaired recognition memory due to defective production of the neurosteroid precursor pregnenolone in the hypothalamus. Genetic interference with pregnenolone synthesis by Star deletion in hypothalamic POMC, but not AgRP neurons, deteriorated recognition memory independently of metabolic disturbances. Our data suggest that pregnenolone’s effects on cognitive function were mediated via an autocrine mechanism on POMC neurons, influencing hippocampal long-term potentiation. The relevance of central pregnenolone on cognition was also confirmed in metabolically unhealthy patients with obesity. Our data reveal an unsuspected role for POMC neuron-derived neurosteroids in cognition. These results provide the basis for a framework to investigate new facets of POMC neuron biology with implications for cognitive disorders.This work was supported by the Swiss National Science Foundation (no.176206; NCCR Synapsy grant no.185897) to C.S.; the European Research Council (ERC) advanced grant SYNEME to J.C.B.; Instituto de Salud Carlos III (ISCIII)—Fondo Europeo de Desarrollo Regional (FEDER) (PI17/00296), RETICs Oftared (RD16/0008/0014), and Generalitat de Catalunya (2017SGR737) to X.G.; Ministerio de Ciencia e Innovación (BFU2017-83317-P) to D.S.; Ministerio de Economia, Industria y Competitividad, Maria de Maeztu (MDM-2017-0729) to Institut de Neurociencies, Universitat de Barcelona; ISCIII-FEDER (PI14/01126, PI17/01019), the National Institutes of Health (NIA grants 1R01AG056850-01A1, R21AG056974, and R01AG061566), Fundació La Marató de TV3 (20141210), and Generalitat de Catalunya (SLT006/17/00119) to J.F.; ISCIII-FEDER (PI17/00279 and PI20/0042), Fundació La Marató de TV3 (201614.31), and Generalitat de Catalunya (SLT008/18/00127) to A.J.; Plan Nacional de I+D funded by the Agencia Estatal de Investigación (AEI) and FEDER (PID2019-111669RB-I00 and PID2020-115055RB-I00), CIBEREHD, the center grant P50AA011999 Southern California Research Center for ALPD and Cirrhosis funded by NIAAA/NIH, Generalitat de Catalunya (SGR-2017-1112), the European Cooperation in Science & Technology (COST) ACTION CA17112, FUNDACIÓN BBVA (“ER stress-mitochondrial cholesterol axis in obesity-associated insulin resistance and comorbidities”), and Red Nacional 2018-102799-T de Enfermedades Metabólicas y Cáncer and Fundació La Marató de TV3 (201916/31) to J.C.F.-C.; and ERC consolidator grant MITOSENSING (725004), ISCIII-FEDER (PI16/00963), “la Caixa” Foundation (ID100010434) under agreement LCF/PR/HR19/52160016, and CERCA Programme/Generalitat de Catalunya to M.C. D.A. is supported by ISCIII (INT19/00016) and Generalitat de Catalunya PERIS program (SLT006/17/125), A.P. is supported by Hospital Clínic de Barcelona (“Ajut Josep Font”), A.O. is supported by a Miguel Servet contract (CP19/00083) from ISCIII-FEDER, and R.H.-T. is supported by a Marie Skłodowska-Curie Action fellowship (H2020-MSCA-IF) and NEUROPREG (891247). S.R. is a recipient of Juan de la Cierva Formación (FJCI-2016-28911) and Incorporación (IJC2018-037341-I) programs from the Spanish Ministry of Science and Innovation. This work was carried out in part at Esther Koplowitz Centre.Peer reviewe

Mitochondrial cristae-remodeling protein OPA1 in POMC neurons couples Ca2+ homeostasis with adipose tissue lipolysis

© 2021 The Authors.Appropriate cristae remodeling is a determinant of mitochondrial function and bioenergetics and thus represents a crucial process for cellular metabolic adaptations. Here, we show that mitochondrial cristae architecture and expression of the master cristae-remodeling protein OPA1 in proopiomelanocortin (POMC) neurons, which are key metabolic sensors implicated in energy balance control, is affected by fluctuations in nutrient availability. Genetic inactivation of OPA1 in POMC neurons causes dramatic alterations in cristae topology, mitochondrial Ca2+ handling, reduction in alpha-melanocyte stimulating hormone (α-MSH) in target areas, hyperphagia, and attenuated white adipose tissue (WAT) lipolysis resulting in obesity. Pharmacological blockade of mitochondrial Ca2+ influx restores α-MSH and the lipolytic program, while improving the metabolic defects of mutant mice. Chemogenetic manipulation of POMC neurons confirms a role in lipolysis control. Our results unveil a novel axis that connects OPA1 in POMC neurons with mitochondrial cristae, Ca2+ homeostasis, and WAT lipolysis in the regulation of energy balance.This work was supported by Agencia Estatal de Investigación y Fondo Social Europeo, Proyecto BFU2016-76973-R FEDER (C.V.A.); AG052005, AG052986, AG051459, DK111178 from NIH and NKFI-KKP-126998 from Hungarian National Research, Development and Innovation Office (T.L.H.); MR/P009824/2 from Medical Research Council UK (G.D.); and Ayudas Fundación BBVA a Investigadores y Creadores Culturales (2015), European Research Council (ERC) under the European Union’s Horizon 2020 Research And Innovation Program (grant agreement 725004) and CERCA Programme/Generalitat de Catalunya (M.C.). A.O. is supported by a Miguel Servet contract (CP19/00083) from Instituto de Salud Carlos III and co-financed by FEDER

Hypothalamic pregnenolone mediates recognition memory in the context of metabolic disorders

Obesity and type-2 diabetes are associated with cognitive dysfunction. Since the hypothalamus is implicated in energy balance control and memory disorders, we hypothesized that specific neurons in this brain region are at the interface of metabolism and cognition. Acute obesogenic diet administration in mice impaired recognition memory due to defective production of the neurosteroid-precursor pregnenolone in the hypothalamus. Genetic interference with pregnenolone synthesis by Star deletion in hypothalamic POMC, but not AgRP neurons, deteriorated recognition memory independently of metabolic disturbances. Our data suggested that pregnenolone's effects on cognitive function were mediated via an autocrine mechanism on POMC neurons, influencing hippocampal long-term potentiation. The relevance of central pregnenolone on cognition was also confirmed in metabolically-unhealthy obese patients. Our data reveals an unsuspected role for POMC neuron-derived neurosteroids in cognition. These results provide the basis for a framework to investigate new facets of POMC neuron biology with implications for cognitive disorders

Mitochondrial cristae-remodeling protein OPA1 in POMC neurons couples Ca2+ homeostasis with adipose tissue lipolysis

Appropriate cristae remodeling is a determinant of mitochondrial function and bioenergetics and thus represents a crucial process for cellular metabolic adaptations. Here, we show that mitochondrial cristae architecture and expression of the master cristae-remodeling protein OPA1 in proopiomelanocortin (POMC) neurons, which are key metabolic sensors implicated in energy balance control, is affected by fluctuations in nutrient availability. Genetic inactivation of OPA1 in POMC neurons causes dramatic alterations in cristae topology, mitochondrial Ca2+ handling, reduction in alpha-melanocyte stimulating hormone (α-MSH) in target areas, hyperphagia, and attenuated white adipose tissue (WAT) lipolysis resulting in obesity. Pharmacological blockade of mitochondrial Ca2+ influx restores α-MSH and the lipolytic program, while improving the metabolic defects of mutant mice. Chemogenetic manipulation of POMC neurons confirms a role in lipolysis control. Our results unveil a novel axis that connects OPA1 in POMC neurons with mitochondrial cristae, Ca2+ homeostasis, and WAT lipolysis in the regulation of energy balance

Etude structurale et fonctionnelle de la variante d'histone H2AZ

The histone variant H2AZ has emerged as a key regulator of chromatin function and plays an essential role in transcriptional activation, cell proliferation, development, and differentiation. H2AZ marks nucleosomes flanking the promoters of most genes, but the mechanistic basis for this localization is unknown. A mechanistic understanding of nucleosome assembly/disassembly requiresa detailed knowledge of nucleosome thermodynamics and histone chaperones. The aim of my thesis was to identify specific chaperone involved in H2AZ dynamic by using biochemical and proteomic strategies. To elucidate the mechanism of H2AZ deposition/eviction, I purified the prenucelosomal H2AZ complex and characterized in details the interacting protein partners. I found that Anp32e is a member of the presumed H2A.Z histone-exchange complex p400/TIP60. Bacterially expressed Anp32e binds only to the H2AZ/H2B dimers but not to the H2A/H2B. Anp32e interacts with a short region of the docking domain of H2A.Z. The binding occurred through a novel Anp32e motif, termed ZID. Finally, I show that down regulation of Anp32e interferes with both the de-repression of hormone dependent genes and H2A.Z removal from their promoter. Our data identified Anp32e as a novel mammalian H2AZ chaperone invoved in H2AZ eviction.La variante d’histone H2AZ joue un rôle important dans l’activation de la transcription, la prolifération cellulaire, le développement et la différentiation. H2AZ orne les promoteurs de la majorité des gènes, mais les mécanismes de bases de cette localisation sont inconnus. La compréhension de l’assemblage et du désassemblage du nucléosome passe par la caractérisation de la dynamique du nucléosome et des chaperonnes d’histones. L’objectif de ma thèse était d’identifier des chaperonnes spécifiques impliqués dans la dynamique de H2AZ en utilisant une approche de protéomique. Pour élucider les mécanismes de déposition/éviction de H2AZ, j’ai purifié le complexe prénucléosomale de H2AZ et j’ai caractérisé toutes les protéines associées. J’ai trouvé que Anp32e fait partie du complexe p400/TIP60 qui est présumée pour être responsable de l’échange d’H2AZ sur la chromatine. Anp32e présente une spécificité pour le dimère H2AZ-H2B, car il n’interagit pas avec le dimère H2A-H2B. L’interaction est accomplie au niveau d’une petite région dans le domaine d’ancrage sur H2AZ et au niveau d’un nouveau domaine ZID sur Anp32e. Finalement, j’ai montré que la suppression d’Anp32e entraine : un défaut dans la dé-répression des gènes dont l’expression est contrôlée par une hormone et une accumulation sur les promoteurs de ces derniers. Dans l’ensemble ces résultats identifient Anp32e comme une nouvelle chaperonne de la variante d’histoneH2AZ impliquée dans l’éviction de H2AZ chez les mammifères

Structural and functional study of the histone variant H2AZ

La variante d’histone H2AZ joue un rôle important dans l’activation de la transcription, la prolifération cellulaire, le développement et la différentiation. H2AZ orne les promoteurs de la majorité des gènes, mais les mécanismes de bases de cette localisation sont inconnus. La compréhension de l’assemblage et du désassemblage du nucléosome passe par la caractérisation de la dynamique du nucléosome et des chaperonnes d’histones. L’objectif de ma thèse était d’identifier des chaperonnes spécifiques impliqués dans la dynamique de H2AZ en utilisant une approche de protéomique. Pour élucider les mécanismes de déposition/éviction de H2AZ, j’ai purifié le complexe prénucléosomale de H2AZ et j’ai caractérisé toutes les protéines associées. J’ai trouvé que Anp32e fait partie du complexe p400/TIP60 qui est présumée pour être responsable de l’échange d’H2AZ sur la chromatine. Anp32e présente une spécificité pour le dimère H2AZ-H2B, car il n’interagit pas avec le dimère H2A-H2B. L’interaction est accomplie au niveau d’une petite région dans le domaine d’ancrage sur H2AZ et au niveau d’un nouveau domaine ZID sur Anp32e. Finalement, j’ai montré que la suppression d’Anp32e entraine : un défaut dans la dé-répression des gènes dont l’expression est contrôlée par une hormone et une accumulation sur les promoteurs de ces derniers. Dans l’ensemble ces résultats identifient Anp32e comme une nouvelle chaperonne de la variante d’histoneH2AZ impliquée dans l’éviction de H2AZ chez les mammifères.The histone variant H2AZ has emerged as a key regulator of chromatin function and plays an essential role in transcriptional activation, cell proliferation, development, and differentiation. H2AZ marks nucleosomes flanking the promoters of most genes, but the mechanistic basis for this localization is unknown. A mechanistic understanding of nucleosome assembly/disassembly requiresa detailed knowledge of nucleosome thermodynamics and histone chaperones. The aim of my thesis was to identify specific chaperone involved in H2AZ dynamic by using biochemical and proteomic strategies. To elucidate the mechanism of H2AZ deposition/eviction, I purified the prenucelosomal H2AZ complex and characterized in details the interacting protein partners. I found that Anp32e is a member of the presumed H2A.Z histone-exchange complex p400/TIP60. Bacterially expressed Anp32e binds only to the H2AZ/H2B dimers but not to the H2A/H2B. Anp32e interacts with a short region of the docking domain of H2A.Z. The binding occurred through a novel Anp32e motif, termed ZID. Finally, I show that down regulation of Anp32e interferes with both the de-repression of hormone dependent genes and H2A.Z removal from their promoter. Our data identified Anp32e as a novel mammalian H2AZ chaperone invoved in H2AZ eviction

Etude structurale et fonctionnelle de la variante d'histone H2AZ

La variante d histone H2AZ joue un rôle important dans l activation de la transcription, la prolifération cellulaire, le développement et la différentiation. H2AZ orne les promoteurs de la majorité des gènes, mais les mécanismes de bases de cette localisation sont inconnus. La compréhension de l assemblage et du désassemblage du nucléosome passe par la caractérisation de la dynamique du nucléosome et des chaperonnes d histones. L objectif de ma thèse était d identifier des chaperonnes spécifiques impliqués dans la dynamique de H2AZ en utilisant une approche de protéomique. Pour élucider les mécanismes de déposition/éviction de H2AZ, j ai purifié le complexe prénucléosomale de H2AZ et j ai caractérisé toutes les protéines associées. J ai trouvé que Anp32e fait partie du complexe p400/TIP60 qui est présumée pour être responsable de l échange d H2AZ sur la chromatine. Anp32e présente une spécificité pour le dimère H2AZ-H2B, car il n interagit pas avec le dimère H2A-H2B. L interaction est accomplie au niveau d une petite région dans le domaine d ancrage sur H2AZ et au niveau d un nouveau domaine ZID sur Anp32e. Finalement, j ai montré que la suppression d Anp32e entraine : un défaut dans la dé-répression des gènes dont l expression est contrôlée par une hormone et une accumulation sur les promoteurs de ces derniers. Dans l ensemble ces résultats identifient Anp32e comme une nouvelle chaperonne de la variante d histoneH2AZ impliquée dans l éviction de H2AZ chez les mammifères.The histone variant H2AZ has emerged as a key regulator of chromatin function and plays an essential role in transcriptional activation, cell proliferation, development, and differentiation. H2AZ marks nucleosomes flanking the promoters of most genes, but the mechanistic basis for this localization is unknown. A mechanistic understanding of nucleosome assembly/disassembly requiresa detailed knowledge of nucleosome thermodynamics and histone chaperones. The aim of my thesis was to identify specific chaperone involved in H2AZ dynamic by using biochemical and proteomic strategies. To elucidate the mechanism of H2AZ deposition/eviction, I purified the prenucelosomal H2AZ complex and characterized in details the interacting protein partners. I found that Anp32e is a member of the presumed H2A.Z histone-exchange complex p400/TIP60. Bacterially expressed Anp32e binds only to the H2AZ/H2B dimers but not to the H2A/H2B. Anp32e interacts with a short region of the docking domain of H2A.Z. The binding occurred through a novel Anp32e motif, termed ZID. Finally, I show that down regulation of Anp32e interferes with both the de-repression of hormone dependent genes and H2A.Z removal from their promoter. Our data identified Anp32e as a novel mammalian H2AZ chaperone invoved in H2AZ eviction.STRASBOURG-Bib.electronique 063 (674829902) / SudocSudocFranceF