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Sundaresan S, Meininger CA, Kang AJ, Photenhauer AL, Hayes MM, Sahoo N, Grembecka J, Cierpicki T, Ding L, Giordano TJ, Else T, Madrigal DJ, Low MJ, Campbell F, Baker AM, Xu H, Wright NA, Merchant JL. Gastrin Induces Nuclear Export and Proteasome Degradation of Menin in Enteric Glial Cells. Gastroenterology 2017; 153:1555-1567.e15. [PMID: 28859856 PMCID: PMC5705278 DOI: 10.1053/j.gastro.2017.08.038] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 07/31/2017] [Accepted: 08/13/2017] [Indexed: 12/21/2022]
Abstract
BACKGROUND & AIMS The multiple endocrine neoplasia, type 1 (MEN1) locus encodes the nuclear protein and tumor suppressor menin. MEN1 mutations frequently cause neuroendocrine tumors such as gastrinomas, characterized by their predominant duodenal location and local metastasis at time of diagnosis. Diffuse gastrin cell hyperplasia precedes the appearance of MEN1 gastrinomas, which develop within submucosal Brunner's glands. We investigated how menin regulates expression of the gastrin gene and induces generation of submucosal gastrin-expressing cell hyperplasia. METHODS Primary enteric glial cultures were generated from the VillinCre:Men1FL/FL:Sst-/- mice or C57BL/6 mice (controls), with or without inhibition of gastric acid by omeprazole. Primary enteric glial cells from C57BL/6 mice were incubated with gastrin and separated into nuclear and cytoplasmic fractions. Cells were incubated with forskolin and H89 to activate or inhibit protein kinase A (a family of enzymes whose activity depends on cellular levels of cyclic AMP). Gastrin was measured in blood, tissue, and cell cultures using an ELISA. Immunoprecipitation with menin or ubiquitin was used to demonstrate post-translational modification of menin. Primary glial cells were incubated with leptomycin b and MG132 to block nuclear export and proteasome activity, respectively. We obtained human duodenal, lymph node, and pancreatic gastrinoma samples, collected from patients who underwent surgery from 1996 through 2007 in the United States or the United Kingdom. RESULTS Enteric glial cells that stained positive for glial fibrillary acidic protein (GFAP+) expressed gastrin de novo through a mechanism that required PKA. Gastrin-induced nuclear export of menin via cholecystokinin B receptor (CCKBR)-mediated activation of PKA. Once exported from the nucleus, menin was ubiquitinated and degraded by the proteasome. GFAP and other markers of enteric glial cells (eg, p75 and S100B), colocalized with gastrin in human duodenal gastrinomas. CONCLUSIONS MEN1-associated gastrinomas, which develop in the submucosa, might arise from enteric glial cells through hormone-dependent PKA signaling. This pathway disrupts nuclear menin function, leading to hypergastrinemia and associated sequelae.
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Affiliation(s)
- Sinju Sundaresan
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Cameron A Meininger
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Anthony J Kang
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Amanda L Photenhauer
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Michael M Hayes
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Nirakar Sahoo
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Jolanta Grembecka
- Department of Pathology, University of Michigan, Ann Arbor, Michigan
| | - Tomasz Cierpicki
- Department of Pathology, University of Michigan, Ann Arbor, Michigan
| | - Lin Ding
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Thomas J Giordano
- Department of Pathology, University of Michigan, Ann Arbor, Michigan
| | - Tobias Else
- Division of Metabolism Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan
| | - David J Madrigal
- Endocrine Oncology Program, University of Michigan, Ann Arbor, Michigan
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Fiona Campbell
- Department of Pathology, Royal Liverpool University Hospital, Liverpool, United Kingdom
| | - Ann-Marie Baker
- Center for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom
| | - Haoxing Xu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Nicholas A Wright
- Center for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom
| | - Juanita L Merchant
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan.
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