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Gomi H, Nagumo T, Asano K, Konosu M, Yasui T, Torii S, Hosaka M. Differential Expression of Secretogranins II and III in Canine Adrenal Chromaffin Cells and Pheochromocytomas. J Histochem Cytochem 2022; 70:335-356. [PMID: 35400231 PMCID: PMC9058372 DOI: 10.1369/00221554221091000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Secretogranin II (SgII) and III (SgIII) function within peptide hormone-producing cells and are involved in secretory granule formation. However, their function in active amine-producing cells is not fully understood. In this study, we analyzed the expression profiles of SgII and SgIII in canine adrenal medulla and pheochromocytomas by immunohistochemical staining. In normal adrenal tissues, the intensity of coexpression of these two secretogranins (Sgs) differed from each chromaffin cell, although a complete match was not observed. The coexpression of vesicular monoamine transporter 2 (VMAT2) with SgIII was similar to that with chromogranin A, but there was a subpopulation of VMAT2-expressing cells that were negative or hardly detectable for SgII. These results are the first to indicate that there are distinct expression patterns for SgII and SgIII in adrenal chromaffin cells. Furthermore, the expression of these two Sgs varied in intensity among pheochromocytomas and did not necessarily correlate with clinical plasma catecholamine levels in patients. However, compared with SgIII, the expression of SgII was shown to be strong at the single-cell level in some tumor tissues. These findings provide a fundamental understanding of the expression differences between SgII and SgIII in normal adrenal chromaffin cells and pheochromocytomas.
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Affiliation(s)
- Hiroshi Gomi
- Department of Veterinary Anatomy, College of Bioresource Sciences
| | - Takahiro Nagumo
- Department of Veterinary Surgery, College of Bioresource Sciences.,Nihon University, Fujisawa, Japan; Division of Companion Animal Surgery, Veterinary Teaching Hospital, Faculty of Agriculture, Iwate University, Morioka, Japan
| | - Kazushi Asano
- Department of Veterinary Surgery, College of Bioresource Sciences
| | - Makoto Konosu
- Department of Veterinary Anatomy, College of Bioresource Sciences
| | - Tadashi Yasui
- Department of Veterinary Anatomy, College of Bioresource Sciences
| | - Seiji Torii
- Center for Food Science and Wellness, Gunma University, Maebashi, Japan
| | - Masahiro Hosaka
- Department of Biotechnology, Faculty of Bioresource Sciences, Akita Prefectural University, Akita, Japan
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Germanos M, Gao A, Taper M, Yau B, Kebede MA. Inside the Insulin Secretory Granule. Metabolites 2021; 11:metabo11080515. [PMID: 34436456 PMCID: PMC8401130 DOI: 10.3390/metabo11080515] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 08/03/2021] [Accepted: 08/03/2021] [Indexed: 12/19/2022] Open
Abstract
The pancreatic β-cell is purpose-built for the production and secretion of insulin, the only hormone that can remove glucose from the bloodstream. Insulin is kept inside miniature membrane-bound storage compartments known as secretory granules (SGs), and these specialized organelles can readily fuse with the plasma membrane upon cellular stimulation to release insulin. Insulin is synthesized in the endoplasmic reticulum (ER) as a biologically inactive precursor, proinsulin, along with several other proteins that will also become members of the insulin SG. Their coordinated synthesis enables synchronized transit through the ER and Golgi apparatus for congregation at the trans-Golgi network, the initiating site of SG biogenesis. Here, proinsulin and its constituents enter the SG where conditions are optimized for proinsulin processing into insulin and subsequent insulin storage. A healthy β-cell is continually generating SGs to supply insulin in vast excess to what is secreted. Conversely, in type 2 diabetes (T2D), the inability of failing β-cells to secrete may be due to the limited biosynthesis of new insulin. Factors that drive the formation and maturation of SGs and thus the production of insulin are therefore critical for systemic glucose control. Here, we detail the formative hours of the insulin SG from the luminal perspective. We do this by mapping the journey of individual members of the SG as they contribute to its genesis.
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Gomi H, Hinata A, Yasui T, Torii S, Hosaka M. Expression Pattern of the LacZ Reporter in Secretogranin III Gene-trapped Mice. J Histochem Cytochem 2021; 69:229-243. [PMID: 33622062 DOI: 10.1369/0022155421996845] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Secretogranin III (SgIII) is a granin protein involved in secretory granule formation in peptide-hormone-producing endocrine cells. In this study, we analyzed the expression of the LacZ reporter in the SgIII knockout mice produced by gene trapping (SgIII-gtKO) for the purpose of comprehensively clarifying the expression patterns of SgIII at the cell and tissue levels. In the endocrine tissues of SgIII-gtKO mice, LacZ expression was observed in the pituitary gland, adrenal medulla, and pancreatic islets, where SgIII expression has been canonically revealed. LacZ expression was extensively observed in brain regions, especially in the cerebral cortex, hippocampus, hypothalamic nuclei, cerebellum, and spinal cord. In peripheral nervous tissues, LacZ expression was observed in the retina, optic nerve, and trigeminal ganglion. LacZ expression was particularly prominent in astrocytes, in addition to neurons and ependymal cells. In the cerebellum, at least four cell types expressed SgIII under basal conditions. The expression of SgIII in the glioma cell lines C6 and RGC-6 was enhanced by excitatory glutamate treatment. It also became clear that the expression level of SgIII varied among neuron and astrocyte subtypes. These results suggest that SgIII is involved in glial cell function, in addition to neuroendocrine functions, in the nervous system.
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Affiliation(s)
- Hiroshi Gomi
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Japan
| | - Airi Hinata
- Laboratory of Molecular Life Sciences, Department of Biotechnology, Akita Prefectural University, Akita, Japan
| | - Tadashi Yasui
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Japan
| | - Seiji Torii
- Center for Food Science and Wellness, Gunma University, Maebashi, Japan
| | - Masahiro Hosaka
- Laboratory of Molecular Life Sciences, Department of Biotechnology, Akita Prefectural University, Akita, Japan
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Fukuoka H, Shichi H, Yamamoto M, Takahashi Y. The Mechanisms Underlying Autonomous Adrenocorticotropic Hormone Secretion in Cushing's Disease. Int J Mol Sci 2020; 21:ijms21239132. [PMID: 33266265 PMCID: PMC7730156 DOI: 10.3390/ijms21239132] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 11/21/2020] [Accepted: 11/29/2020] [Indexed: 12/16/2022] Open
Abstract
Cushing’s disease caused due to adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas (ACTHomas) leads to hypercortisolemia, resulting in increased morbidity and mortality. Autonomous ACTH secretion is attributed to the impaired glucocorticoid negative feedback (glucocorticoid resistance) response. Interestingly, other conditions, such as ectopic ACTH syndrome (EAS) and non-neoplastic hypercortisolemia (NNH, also known as pseudo-Cushing’s syndrome) also exhibit glucocorticoid resistance. Therefore, to differentiate between these conditions, several dynamic tests, including those with desmopressin (DDAVP), corticotrophin-releasing hormone (CRH), and Dex/CRH have been developed. In normal pituitary corticotrophs, ACTH synthesis and secretion are regulated mainly by CRH and glucocorticoids, which are the ACTH secretion-stimulating and -suppressing factors, respectively. These factors regulate ACTH synthesis and secretion through genomic and non-genomic mechanisms. Conversely, glucocorticoid negative feedback is impaired in ACTHomas, which could be due to the overexpression of 11β-HSD2, HSP90, or TR4, or loss of expression of CABLES1 or nuclear BRG1 proteins. Genetic analysis has indicated the involvement of several genes in the etiology of ACTHomas, including USP8, USP48, BRAF, and TP53. However, the association between glucocorticoid resistance and these genes remains unclear. Here, we review the clinical aspects and molecular mechanisms of ACTHomas and compare them to those of other related conditions.
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Affiliation(s)
- Hidenori Fukuoka
- Division of Diabetes and Endocrinology, Kobe University Hospital, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan;
- Correspondence: ; Tel.: +81-78-382-5861; Fax: +81-78-382-2080
| | - Hiroki Shichi
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan; (H.S.); (Y.T.)
| | - Masaaki Yamamoto
- Division of Diabetes and Endocrinology, Kobe University Hospital, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan;
| | - Yutaka Takahashi
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan; (H.S.); (Y.T.)
- Department of Diabetes and Endocrinology, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan
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Culture in 10% O 2 enhances the production of active hormones in neuro-endocrine cells by up-regulating the expression of processing enzymes. Biochem J 2019; 476:827-842. [PMID: 30787050 DOI: 10.1042/bcj20180832] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 02/17/2019] [Accepted: 02/19/2019] [Indexed: 12/22/2022]
Abstract
To closely mimic physiological conditions, low oxygen cultures have been employed in stem cell and cancer research. Although in vivo oxygen concentrations in tissues are often much lower than ambient 21% O2 (ranging from 3.6 to 12.8% O2), most cell cultures are maintained at 21% O2 To clarify the effects of the O2 culture concentration on the regulated secretion of peptide hormones in neuro-endocrine cells, we examined the changes in the storage and release of peptide hormones in neuro-endocrine cell lines and endocrine tissues cultured in a relatively lower O2 concentration. In both AtT-20 cells derived from the mouse anterior pituitary and freshly prepared mouse pituitaries cultured in 10% O2 for 24 h, the storage and regulated secretion of the mature peptide hormone adrenocorticotropic hormone were significantly increased compared with those in cells and pituitaries cultured in ambient 21% O2, whereas its precursor proopiomelanocortin was not increased in the cells and tissues after being cultured in 10% O2 Simultaneously, the prohormone-processing enzymes PC1/3 and carboxypeptidase E were up-regulated in cells cultured in 10% O2, thus facilitating the conversion of prohormones to their active form. Similarly, culturing the mouse β-cell line MIN6 and islet tissue in 10% O2 also significantly increased the conversion of proinsulin into mature insulin, which was secreted in a regulated manner. These results suggest that culture under 10% O2 is more optimal for endocrine tissues/cells to efficiently generate and secrete active peptide hormones than ambient 21% O2.
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Dominguez N, van Weering JRT, Borges R, Toonen RFG, Verhage M. Dense-core vesicle biogenesis and exocytosis in neurons lacking chromogranins A and B. J Neurochem 2018; 144:241-254. [PMID: 29178418 PMCID: PMC5814729 DOI: 10.1111/jnc.14263] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 11/16/2017] [Accepted: 11/20/2017] [Indexed: 11/26/2022]
Abstract
Chromogranin A and B (Cgs) are considered to be master regulators of cargo sorting for the regulated secretory pathway (RSP) and dense-core vesicle (DCV) biogenesis. To test this, we analyzed the release of neuropeptide Y (NPY)-pHluorin, a live RSP reporter, and the distribution, number, and appearance of DCVs, in mouse hippocampal neurons lacking expression of CHGA and CHGB genes. qRT-PCR analysis showed that expression of other granin family members was not significantly altered in CgA/B-/- neurons. As synaptic maturation of developing neurons depends on secretion of trophic factors in the RSP, we first analyzed neuronal development in standardized neuronal cultures. Surprisingly, dendritic and axonal length, arborization, synapse density, and synaptic vesicle accumulation in synapses were all normal in CgA/B-/- neurons. Moreover, the number of DCVs outside the soma, stained with endogenous marker Secretogranin II, the number of NPY-pHluorin puncta, and the total amount of reporter in secretory compartments, as indicated by pH-sensitive NPY-pHluorin fluorescence, were all normal in CgA/B-/- neurons. Electron microscopy revealed that synapses contained a normal number of DCVs, with a normal diameter, in CgA/B-/- neurons. In contrast, CgA/B-/- chromaffin cells contained fewer and smaller secretory vesicles with a smaller core size, as previously reported. Finally, live-cell imaging at single vesicle resolution revealed a normal number of fusion events upon bursts of action potentials in CgA/B-/- neurons. These events had normal kinetics and onset relative to the start of stimulation. Taken together, these data indicate that the two chromogranins are dispensable for cargo sorting in the RSP and DCV biogenesis in mouse hippocampal neurons.
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Affiliation(s)
- Natalia Dominguez
- Department of Clinical GeneticsCenter for Neurogenomics and Cognitive Research (CNCR)VU University Amsterdam and VU University Medical Center (VUmc)AmsterdamThe Netherlands
| | - Jan R. T. van Weering
- Department of Clinical GeneticsCenter for Neurogenomics and Cognitive Research (CNCR)VU University Amsterdam and VU University Medical Center (VUmc)AmsterdamThe Netherlands
| | - Ricardo Borges
- Unidad de FarmacologíaFacultad de MedicinaUniversidad de la LagunaTenerifeSpain
| | - Ruud F. G. Toonen
- Functional GenomicsCenter for Neurogenomics and Cognitive Research (CNCR)VU University Amsterdam and VU University Medical Center (VUmc)AmsterdamThe Netherlands
| | - Matthijs Verhage
- Department of Clinical GeneticsCenter for Neurogenomics and Cognitive Research (CNCR)VU University Amsterdam and VU University Medical Center (VUmc)AmsterdamThe Netherlands
- Functional GenomicsCenter for Neurogenomics and Cognitive Research (CNCR)VU University Amsterdam and VU University Medical Center (VUmc)AmsterdamThe Netherlands
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Maeda Y, Kudo S, Tsushima K, Sato E, Kubota C, Kayamori A, Bochimoto H, Koga D, Torii S, Gomi H, Watanabe T, Hosaka M. Impaired Processing of Prohormones in Secretogranin III-Null Mice Causes Maladaptation to an Inadequate Diet and Stress. Endocrinology 2018; 159:1213-1227. [PMID: 29281094 DOI: 10.1210/en.2017-00636] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Accepted: 12/15/2017] [Indexed: 11/19/2022]
Abstract
Secretogranin III (SgIII), a member of the granin family, binds both to another granin, chromogranin A (CgA), and to a cholesterol-rich membrane that is destined for secretory granules (SGs). The knockdown of SgIII in adrenocorticotropic hormone (ACTH)-producing AtT-20 cells largely impairs the regulated secretion of CgA and ACTH. To clarify the physiological roles of SgIII in vivo, we analyzed hormone secretion and SG biogenesis in newly established SgIII-knockout (KO) mice. Although the SgIII-KO mice were viable and fertile and exhibited no overt abnormalities under ordinary rearing conditions, a high-fat/high-sucrose diet caused pronounced obesity in the mice. Furthermore, in the SgIII-KO mice compared with wild-type (WT) mice, the stimulated secretion of active insulin decreased substantially, whereas the storage of proinsulin increased in the islets. The plasma ACTH was also less elevated in the SgIII-KO mice than in the WT mice after chronic restraint stress, whereas the storage level of the precursor proopiomelanocortin in the pituitary gland was somewhat increased. These findings suggest that the lack of SgIII causes maladaptation of endocrine cells to an inadequate diet and stress by impairing the proteolytic conversion of prohormones in SGs, whereas SG biogenesis and the basal secretion of peptide hormones under ordinary conditions are ensured by the compensatory upregulation of other residual granins or factors.
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Affiliation(s)
- Yoshinori Maeda
- Department of Biotechnology, Laboratory of Molecular Life Sciences, Akita Prefectural University, Akita, Japan
| | - Saki Kudo
- Department of Biotechnology, Laboratory of Molecular Life Sciences, Akita Prefectural University, Akita, Japan
| | - Ken Tsushima
- Department of Biotechnology, Laboratory of Molecular Life Sciences, Akita Prefectural University, Akita, Japan
| | - Eri Sato
- Department of Biotechnology, Laboratory of Molecular Life Sciences, Akita Prefectural University, Akita, Japan
| | - Chisato Kubota
- Biosignal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
- Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan
| | - Aika Kayamori
- Department of Biotechnology, Laboratory of Molecular Life Sciences, Akita Prefectural University, Akita, Japan
| | - Hiroki Bochimoto
- Health Care Administration Center, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan
| | - Daisuke Koga
- Department of Microscopic Anatomy and Cell Biology, Asahikawa Medical University, Asahikawa, Japan
| | - Seiji Torii
- Biosignal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Hiroshi Gomi
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Japan
| | - Tsuyoshi Watanabe
- Department of Microscopic Anatomy and Cell Biology, Asahikawa Medical University, Asahikawa, Japan
| | - Masahiro Hosaka
- Department of Biotechnology, Laboratory of Molecular Life Sciences, Akita Prefectural University, Akita, Japan
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Schmudlach A, Felton J, Kennedy RT, Dovichi NJ. Bottom-up proteomics analysis of the secretome of murine islets of Langerhans in elevated glucose levels. Analyst 2017; 142:284-291. [PMID: 27966681 DOI: 10.1039/c6an02268e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Glucotoxicity is a causative agent of type-2 diabetes, where high glucose levels damage the islets of Langerhans resulting in oxidative damage and endoplasmic reticulum stress. We evaluated the secretomes of healthy CD-1 murine islets. Three experimental conditions were investigated in biological triplicate: a control incubated with 11 mM glucose, 1-day incubation with 25 mM glucose, and 2-day incubation with 25 mM glucose. An SDS-based, filter-aided sample preparation protocol was used to prepare secretomes for analysis. A total of 428 protein groups were identified across the nine samples. Each condition generated between 328-349 protein IDs and intracondition protein overlap was between 66-90% for the biological triplicates. 232 protein groups were identified in all three conditions with 184 quantified at least once in each condition. Significant expression changes were observed for proteins associated with the unfolded protein response, such as proteases, chaperones, and elongation factors, as well as proteins associated with peptide hormone processing and small molecule metabolism.
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Affiliation(s)
- Andrew Schmudlach
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
| | - Jeremy Felton
- Departments of Chemistry and Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Robert T Kennedy
- Departments of Chemistry and Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Norman J Dovichi
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
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Cawley NX, Li Z, Loh YP. 60 YEARS OF POMC: Biosynthesis, trafficking, and secretion of pro-opiomelanocortin-derived peptides. J Mol Endocrinol 2016; 56:T77-97. [PMID: 26880796 PMCID: PMC4899099 DOI: 10.1530/jme-15-0323] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 02/15/2016] [Indexed: 12/15/2022]
Abstract
Pro-opiomelanocortin (POMC) is a prohormone that encodes multiple smaller peptide hormones within its structure. These peptide hormones can be generated by cleavage of POMC at basic residue cleavage sites by prohormone-converting enzymes in the regulated secretory pathway (RSP) of POMC-synthesizing endocrine cells and neurons. The peptides are stored inside the cells in dense-core secretory granules until released in a stimulus-dependent manner. The complexity of the regulation of the biosynthesis, trafficking, and secretion of POMC and its peptides reflects an impressive level of control over many factors involved in the ultimate role of POMC-expressing cells, that is, to produce a range of different biologically active peptide hormones ready for action when signaled by the body. From the discovery of POMC as the precursor to adrenocorticotropic hormone (ACTH) and β-lipotropin in the late 1970s to our current knowledge, the understanding of POMC physiology remains a monumental body of work that has provided insight into many aspects of molecular endocrinology. In this article, we describe the intracellular trafficking of POMC in endocrine cells, its sorting into dense-core secretory granules and transport of these granules to the RSP. Additionally, we review the enzymes involved in the maturation of POMC to its various peptides and the mechanisms involved in the differential processing of POMC in different cell types. Finally, we highlight studies pertaining to the regulation of ACTH secretion in the anterior and intermediate pituitary and POMC neurons of the hypothalamus.
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Affiliation(s)
- Niamh X Cawley
- Section on Cellular NeurobiologyEunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Zhaojin Li
- Section on Cellular NeurobiologyEunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Y Peng Loh
- Section on Cellular NeurobiologyEunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
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Cawley NX, Rathod T, Young S, Lou H, Birch N, Loh YP. Carboxypeptidase E and Secretogranin III Coordinately Facilitate Efficient Sorting of Proopiomelanocortin to the Regulated Secretory Pathway in AtT20 Cells. Mol Endocrinol 2015; 30:37-47. [PMID: 26646096 DOI: 10.1210/me.2015-1166] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Proopiomelanocortin (POMC) is a multivalent prohormone that can be processed into at least 7 biologically active peptide hormones. Processing can begin in the trans-Golgi network (TGN) and continues in the secretory granules of the regulated secretory pathway (RSP). Sorting of POMC into these granules is a complex process. Previously, a membrane-associated form of carboxypeptidase E (CPE) was shown to bind to POMC and facilitate its trafficking into these granules. More recently, secretogranin III (SgIII) was also found to affect POMC trafficking. Here, we show by RNA silencing that CPE and SgIII play a synergistic role in the trafficking of POMC to granules of the RSP in AtT20 cells. Reduction of either protein resulted in increased constitutive secretion of POMC and chromogranin A, which was increased even further when both proteins were reduced together, indicative of missorting at the TGN. In SgIII-reduced cells, POMC accumulated in a compartment that cofractionated and colocalized with syntaxin 6, a marker of the TGN, on sucrose density gradients and in immunocytochemistry, respectively, indicating an accumulation of this protein in the presumed sorting compartment. Regulated secretion of ACTH, as a measure of sorting and processing of POMC in mature granules, was reduced in the SgIII down-regulated cells but was increased in the CPE down-regulated cells. These results suggest that multiple sorting systems exist, providing redundancy to ensure the important task of continuous and accurate trafficking of prohormones to the granules of the RSP for the production of peptide hormones.
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Affiliation(s)
- Niamh X Cawley
- Section on Cellular Neurobiology (N.X.C., T.R., S.Y., H.L., Y.P.L.), Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4480; and School of Biological Sciences (N.B.), Centre for Brain Research and Brain Research New Zealand, Rangahau Roro Aotearoa, University of Auckland, New Zealand
| | - Trushar Rathod
- Section on Cellular Neurobiology (N.X.C., T.R., S.Y., H.L., Y.P.L.), Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4480; and School of Biological Sciences (N.B.), Centre for Brain Research and Brain Research New Zealand, Rangahau Roro Aotearoa, University of Auckland, New Zealand
| | - Sigrid Young
- Section on Cellular Neurobiology (N.X.C., T.R., S.Y., H.L., Y.P.L.), Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4480; and School of Biological Sciences (N.B.), Centre for Brain Research and Brain Research New Zealand, Rangahau Roro Aotearoa, University of Auckland, New Zealand
| | - Hong Lou
- Section on Cellular Neurobiology (N.X.C., T.R., S.Y., H.L., Y.P.L.), Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4480; and School of Biological Sciences (N.B.), Centre for Brain Research and Brain Research New Zealand, Rangahau Roro Aotearoa, University of Auckland, New Zealand
| | - Nigel Birch
- Section on Cellular Neurobiology (N.X.C., T.R., S.Y., H.L., Y.P.L.), Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4480; and School of Biological Sciences (N.B.), Centre for Brain Research and Brain Research New Zealand, Rangahau Roro Aotearoa, University of Auckland, New Zealand
| | - Y Peng Loh
- Section on Cellular Neurobiology (N.X.C., T.R., S.Y., H.L., Y.P.L.), Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4480; and School of Biological Sciences (N.B.), Centre for Brain Research and Brain Research New Zealand, Rangahau Roro Aotearoa, University of Auckland, New Zealand
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11
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Gomi H, Morikawa S, Shinmura N, Moki H, Yasui T, Tsukise A, Torii S, Watanabe T, Maeda Y, Hosaka M. Expression of Secretogranin III in Chicken Endocrine Cells: Its Relevance to the Secretory Granule Properties of Peptide Prohormone Processing and Bioactive Amine Content. J Histochem Cytochem 2015; 63:350-66. [PMID: 25673289 PMCID: PMC4409946 DOI: 10.1369/0022155415575032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 02/05/2015] [Indexed: 01/27/2023] Open
Abstract
The expression of secretogranin III (SgIII) in chicken endocrine cells has not been investigated. There is limited data available for the immunohistochemical localization of SgIII in the brain, pituitary, and pancreatic islets of humans and rodents. In the present study, we used immunoblotting to reveal the similarities between the expression patterns of SgIII in the common endocrine glands of chickens and rats. The protein-protein interactions between SgIII and chromogranin A (CgA) mediate the sorting of CgA/prohormone core aggregates to the secretory granule membrane. We examined these interactions using co-immunoprecipitation in chicken endocrine tissues. Using immunohistochemistry, we also examined the expression of SgIII in a wide range of chicken endocrine glands and gastrointestinal endocrine cells (GECs). SgIII was expressed in the pituitary, pineal, adrenal (medullary parts), parathyroid, and ultimobranchial glands, but not in the thyroid gland. It was also expressed in GECs of the stomach (proventriculus and gizzard), small and large intestines, and pancreatic islet cells. These SgIII-expressing cells co-expressed serotonin, somatostatin, gastric inhibitory polypeptide, glucagon-like peptide-1, glucagon, or insulin. These results suggest that SgIII is expressed in the endocrine cells that secrete peptide hormones, which mature via the intragranular enzymatic processing of prohormones and physiologically active amines in chickens.
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Affiliation(s)
- Hiroshi Gomi
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Japan (HG, SM, NS, HM, TY, AT)
| | - Satomi Morikawa
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Japan (HG, SM, NS, HM, TY, AT)
| | - Naoki Shinmura
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Japan (HG, SM, NS, HM, TY, AT)
| | - Hiroaki Moki
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Japan (HG, SM, NS, HM, TY, AT)
| | - Tadashi Yasui
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Japan (HG, SM, NS, HM, TY, AT)
| | - Azuma Tsukise
- Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Japan (HG, SM, NS, HM, TY, AT)
| | - Seiji Torii
- Laboratory of Secretion Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan (ST)
| | - Tsuyoshi Watanabe
- Department of Microscopic Anatomy and Cell Biology, Asahikawa Medical College, Asahikawa, Japan (TW)
| | - Yoshinori Maeda
- Laboratory of Molecular Life Sciences, Department of Biotechnology, Akita Prefectural University, Akita, Japan (YM, MH)
| | - Masahiro Hosaka
- Laboratory of Molecular Life Sciences, Department of Biotechnology, Akita Prefectural University, Akita, Japan (YM, MH)
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Guizzetti L, McGirr R, Dhanvantari S. Two dipolar α-helices within hormone-encoding regions of proglucagon are sorting signals to the regulated secretory pathway. J Biol Chem 2014; 289:14968-80. [PMID: 24727476 DOI: 10.1074/jbc.m114.563684] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Proglucagon is expressed in pancreatic α cells, intestinal L cells, and some hypothalamic and brainstem neurons. Tissue-specific processing of proglucagon yields three major peptide hormones as follows: glucagon in the α cells and glucagon-like peptides (GLP)-1 and -2 in the L cells and neurons. Efficient sorting and packaging into the secretory granules of the regulated secretory pathway in each cell type are required for nutrient-regulated secretion of these proglucagon-derived peptides. Our previous work suggested that proglucagon is directed into granules by intrinsic sorting signals after initial processing to glicentin and major proglucagon fragment (McGirr, R., Guizzetti, L., and Dhanvantari, S. (2013) J. Endocrinol. 217, 229-240), leading to the hypothesis that sorting signals may be present in multiple domains. In the present study, we show that the α-helices within glucagon and GLP-1, but not GLP-2, act as sorting signals by efficiently directing a heterologous secretory protein to the regulated secretory pathway. Biophysical characterization of these peptides revealed that glucagon and GLP-1 each encode a nonamphipathic, dipolar α-helix, whereas the helix in GLP-2 is not dipolar. Surprisingly, glicentin and major proglucagon fragment were sorted with different efficiencies, thus providing evidence that proglucagon is first sorted to granules prior to processing. In contrast to many other prohormones in which sorting is directed by ordered prodomains, the sorting determinants of proglucagon lie within the ordered hormone domains of glucagon and GLP-1, illustrating that each prohormone has its own sorting "signature."
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Affiliation(s)
| | - Rebecca McGirr
- the Metabolism/Diabetes and Imaging Programs, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Savita Dhanvantari
- From the Departments of Medical Biophysics, the Metabolism/Diabetes and Imaging Programs, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada Pathology, and Medicine, University of Western Ontario, London, Ontario N6A 3K7 and
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