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Browsing by Author "Bernal-Mizrachi, Ernesto"
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Item Hypusine biosynthesis in β cells links polyamine metabolism to facultative cellular proliferation to maintain glucose homeostasis(American Association for the Advancement of Science, 2019-12-03) Levasseur, Esther M.; Yamada, Kentaro; Piñeros, Annie R.; Wu, Wenting; Syed, Farooq; Orr, Kara S.; Anderson-Baucum, Emily; Mastracci, Teresa L.; Maier, Bernhard; Mosley, Amber L.; Liu, Yunlong; Bernal-Mizrachi, Ernesto; Alonso, Laura C.; Scott, Donald; Garcia-Ocaña, Adolfo; Tersey, Sarah A.; Mirmira, Raghavendra G.; Pediatrics, School of MedicineDeoxyhypusine synthase (DHPS) utilizes the polyamine spermidine to catalyze the hypusine modification of the mRNA translation factor eIF5A and promotes oncogenesis through poorly-defined mechanisms. Because germline deletion of Dhps is embryonically lethal, its role in normal postnatal cellular function in vivo remains unknown. We generated a mouse model that enabled the inducible, postnatal deletion of Dhps specifically in postnatal islet β cells, which function to maintain glucose homeostasis. Removal of Dhps did not have an effect under normal physiologic conditions. However, upon development of insulin resistance, which induces β-cell proliferation, Dhps deletion caused alterations in proteins required for mRNA translation and protein secretion, reduced production of the cell cycle molecule cyclin D2, impaired β-cell proliferation, and induced overt diabetes. We found that hypusine biosynthesis was downstream of protein kinase C-ζ and was required for c-Myc-induced proliferation. Our studies reveal a requirement for DHPS in β cells to link polyamines to mRNA translation to effect facultative cellular proliferation and glucose homeostasis.Item Integrated Physiology of the Exocrine and Endocrine Compartments in Pancreatic Diseases: Workshop Proceedings(Wolters Kluwer, 2022) Mastracci, Teresa L.; Apte, Minoti; Amundadottir, Laufey T.; Alvarsson, Alexandra; Artandi, Steven; Bellin, Melena D.; Bernal-Mizrachi, Ernesto; Caicedo, Alejandro; Campbell-Thompson, Martha; Cruz-Monserrate, Zobeida; El Ouaamari, Abdelfattah; Gaulton, Kyle J.; Geisz, Andrea; Goodarzi, Mark O.; Hara, Manami; Hull-Meichle, Rebecca L.; Kleger, Alexander; Klein, Alison P.; Kopp, Janel L.; Kulkarni, Rohit N.; Muzumdar, Mandar D.; Naren, Anjaparavanda P.; Oakes, Scott A.; Olesen, Søren S.; Phelps, Edward A.; Powers, Alvin C.; Stabler, Cherie L.; Tirkes, Temel; Whitcomb, David C.; Yadav, Dhiraj; Yong, Jing; Zaghloul, Norann A.; Sander, Maike; Pandol, Stephen J.; Biology, School of ScienceThe Integrated Physiology of the Exocrine and Endocrine Compartments in Pancreatic Diseases Workshop was a 1.5-day scientific conference at the National Institutes of Health (Bethesda, MD) that engaged clinical and basic science investigators interested in diseases of the pancreas. This report summarizes the workshop proceedings. The goal of the workshop was to forge connections and identify gaps in knowledge that could guide future research directions. Presentations were segregated into six major themes, including: (a) Pancreas Anatomy and Physiology; (b) Diabetes in the Setting of Exocrine Disease; (c) Metabolic Influences on the Exocrine Pancreas; (d) Genetic Drivers of Pancreatic Diseases; (e) Tools for Integrated Pancreatic Analysis; and (f) Implications of Exocrine-Endocrine Crosstalk. For each theme, there were multiple presentations followed by panel discussions on specific topics relevant to each area of research; these are summarized herein. Significantly, the discussions resulted in the identification of research gaps and opportunities for the field to address. In general, it was concluded that as a pancreas research community, we must more thoughtfully integrate our current knowledge of the normal physiology as well as the disease mechanisms that underlie endocrine and exocrine disorders so that there is a better understanding of the interplay between these compartments.Item Loss of mTORC1 signalling impairs β-cell homeostasis and insulin processing(Nature Communication Group, 2017-07-12) Blandino-Rosano, Manuel; Barbaresso, Rebecca; Jimenez-Palomares, Margarita; Bozadjieva, Nadejda; Werneck-de-Castro, Joao Pedro; Hatanaka, Masayuki; Mirmira, Raghavendra G.; Sonenberg, Nahum; Liu, Ming; Rüegg, Markus A.; Hall, Michael N.; Bernal-Mizrachi, Ernesto; Pediatrics, School of MedicineDeregulation of mTOR complex 1 (mTORC1) signalling increases the risk for metabolic diseases, including type 2 diabetes. Here we show that β-cell-specific loss of mTORC1 causes diabetes and β-cell failure due to defects in proliferation, autophagy, apoptosis and insulin secretion by using mice with conditional (βraKO) and inducible (MIP-βraKOf/f) raptor deletion. Through genetic reconstitution of mTORC1 downstream targets, we identify mTORC1/S6K pathway as the mechanism by which mTORC1 regulates β-cell apoptosis, size and autophagy, whereas mTORC1/4E-BP2-eIF4E pathway regulates β-cell proliferation. Restoration of both pathways partially recovers β-cell mass and hyperglycaemia. This study also demonstrates a central role of mTORC1 in controlling insulin processing by regulating cap-dependent translation of carboxypeptidase E in a 4EBP2/eIF4E-dependent manner. Rapamycin treatment decreases CPE expression and insulin secretion in mice and human islets. We suggest an important role of mTORC1 in β-cells and identify downstream pathways driving β-cell mass, function and insulin processing.