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Merkler DJ, Hawley AJ, Eipper BA, Mains RE. Peptidylglycine α-amidating monooxygenase as a therapeutic target or biomarker for human diseases. Br J Pharmacol 2022; 179:3306-3324. [PMID: 35124797 PMCID: PMC9177522 DOI: 10.1111/bph.15815] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 01/10/2022] [Accepted: 01/12/2022] [Indexed: 01/20/2024] Open
Abstract
Peptides play a key role in controlling many physiological and neurobiological pathways. Many bioactive peptides require a C-terminal α-amide for full activity. The bifunctional enzyme catalysing α-amidation, peptidylglycine α-amidating monooxygenase (PAM), is the sole enzyme responsible for amidated peptide biosynthesis, from Chlamydomonas reinhardtii to Homo sapiens. Many neuronal and endocrine functions are dependent upon amidated peptides; additional amidated peptides are growth promoters in tumours. The amidation reaction occurs in two steps, glycine α-hydroxylation followed by dealkylation to generate the α-amide product. Currently, most potentially useful inhibitors target the first reaction, which is rate-limiting. PAM is a membrane-bound enzyme that visits the cell surface during peptide secretion. PAM is then used again in the biosynthetic pathway, meaning that cell-impermeable inhibitors or inactivators could have therapeutic value for the treatment of cancer or psychiatric abnormalities. To date, inhibitor design has not fully exploited the structures and mechanistic details of PAM.
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Affiliation(s)
- David J Merkler
- Department of Chemistry, University of South Florida, 4202 E. Fowler Ave., Tampa, FL 33620, USA
| | - Aidan J Hawley
- Department of Chemistry, University of South Florida, 4202 E. Fowler Ave., Tampa, FL 33620, USA
| | - Betty A Eipper
- Department of Molecular Biology & Biophysics, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT, 06030 USA
- Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT, 06030 USA
| | - Richard E Mains
- Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT, 06030 USA
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2
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Rao VKS, Eipper BA, Mains RE. Multiple roles for peptidylglycine α-amidating monooxygenase in the response to hypoxia. J Cell Physiol 2021; 236:7745-7758. [PMID: 34061983 DOI: 10.1002/jcp.30457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 05/10/2021] [Accepted: 05/19/2021] [Indexed: 11/11/2022]
Abstract
The biosynthesis of many of the peptides involved in homeostatic control requires peptidylglycine α-amidating monooxygenase (PAM), an ancient, highly conserved copper- and ascorbate-dependent enzyme. Using the production of amidated chromogranin A to monitor PAM function in tumor cells, physiologically relevant levels of hypoxia were shown to inhibit this monooxygenase. The ability of primary pituitary cells exposed to hypoxic conditions for 4 h to produce amidated chromogranin A was similarly inhibited. The affinity of the purified monooxygenase for oxygen (Km = 99 ± 19 μM) was consistent with this result. The ability of PAM to alter secretory pathway behavior under normoxic conditions required its monooxygenase activity. Under normoxic conditions, hypoxia-inducible factor 1a levels in dense cultures of corticotrope tumor cells expressing high levels of PAM exceeded those in control cells; expression of inactive monooxygenase did not have this effect. The effects of hypoxia on levels of two PAM-regulated genes (activating transcription factor 3 [Atf3] and FK506 binding protein 2 [Fkbp2]) differed in cells expressing high versus low levels of PAM. Putative hypoxia response elements occur in both human and mouse PAM, and hPAM has consistently been identified as one of the genes upregulated in response to hypoxia. Expression of PAM is also known to alter gene expression. A quarter of the genes consistently upregulated in response to hypoxia were downregulated following increased expression of PAM. Taken together, our data suggest roles for PAM and amidated peptide secretion in the coordination of tissue-specific responses to hypoxia.
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Affiliation(s)
- Vishwanatha K S Rao
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut, USA
| | - Betty A Eipper
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut, USA.,Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, Connecticut, USA
| | - Richard E Mains
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut, USA
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3
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Simpson PD, Eipper BA, Katz MJ, Gandara L, Wappner P, Fischer R, Hodson EJ, Ratcliffe PJ, Masson N. Striking Oxygen Sensitivity of the Peptidylglycine α-Amidating Monooxygenase (PAM) in Neuroendocrine Cells. J Biol Chem 2015; 290:24891-901. [PMID: 26296884 PMCID: PMC4598998 DOI: 10.1074/jbc.m115.667246] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Indexed: 01/23/2023] Open
Abstract
Interactions between biological pathways and molecular oxygen require robust mechanisms for detecting and responding to changes in cellular oxygen availability, to support oxygen homeostasis. Peptidylglycine α-amidating monooxygenase (PAM) catalyzes a two-step reaction resulting in the C-terminal amidation of peptides, a process important for their stability and biological activity. Here we show that in human, mouse, and insect cells, peptide amidation is exquisitely sensitive to hypoxia. Different amidation events on chromogranin A, and on peptides processed from proopiomelanocortin, manifest similar striking sensitivity to hypoxia in a range of neuroendocrine cells, being progressively inhibited from mild (7% O2) to severe (1% O2) hypoxia. In developing Drosophila melanogaster larvae, FMRF amidation in thoracic ventral (Tv) neurons is strikingly suppressed by hypoxia. Our findings have thus defined a novel monooxygenase-based oxygen sensing mechanism that has the capacity to signal changes in oxygen availability to peptidergic pathways.
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Affiliation(s)
- Peter D Simpson
- From the Centre for Cellular and Molecular Physiology, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Betty A Eipper
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030
| | | | - Lautaro Gandara
- Fundacion Instituto Leloir, C1405BWE Buenos Aires, Argentina, and
| | - Pablo Wappner
- Fundacion Instituto Leloir, C1405BWE Buenos Aires, Argentina, and
| | - Roman Fischer
- Target Discovery Institute, University of Oxford, Oxford OX3 7FZ, United Kingdom
| | - Emma J Hodson
- From the Centre for Cellular and Molecular Physiology, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Peter J Ratcliffe
- From the Centre for Cellular and Molecular Physiology, University of Oxford, Oxford OX3 7BN, United Kingdom,
| | - Norma Masson
- From the Centre for Cellular and Molecular Physiology, University of Oxford, Oxford OX3 7BN, United Kingdom,
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4
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Bonnemaison ML, Bäck N, Duffy ME, Ralle M, Mains RE, Eipper BA. Adaptor Protein-1 Complex Affects the Endocytic Trafficking and Function of Peptidylglycine α-Amidating Monooxygenase, a Luminal Cuproenzyme. J Biol Chem 2015; 290:21264-79. [PMID: 26170456 DOI: 10.1074/jbc.m115.641027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Indexed: 11/06/2022] Open
Abstract
The adaptor protein-1 complex (AP-1), which transports cargo between the trans-Golgi network and endosomes, plays a role in the trafficking of Atp7a, a copper-transporting P-type ATPase, and peptidylglycine α-amidating monooxygenase (PAM), a copper-dependent membrane enzyme. Lack of any of the four AP-1 subunits impairs function, and patients with MEDNIK syndrome, a rare genetic disorder caused by lack of expression of the σ1A subunit, exhibit clinical and biochemical signs of impaired copper homeostasis. To explore the role of AP-1 in copper homeostasis in neuroendocrine cells, we used corticotrope tumor cells in which AP-1 function was diminished by reducing expression of its μ1A subunit. Copper levels were unchanged when AP-1 function was impaired, but cellular levels of Atp7a declined slightly. The ability of PAM to function was assessed by monitoring 18-kDa fragment-NH2 production from proopiomelanocortin. Reduced AP-1 function made 18-kDa fragment amidation more sensitive to inhibition by bathocuproine disulfonate, a cell-impermeant Cu(I) chelator. The endocytic trafficking of PAM was altered, and PAM-1 accumulated on the cell surface when AP-1 levels were reduced. Reduced AP-1 function increased the Atp7a presence in early/recycling endosomes but did not alter the ability of copper to stimulate its appearance on the plasma membrane. Co-immunoprecipitation of a small fraction of PAM and Atp7a supports the suggestion that copper can be transferred directly from Atp7a to PAM, a process that can occur only when both proteins are present in the same subcellular compartment. Altered luminal cuproenzyme function may contribute to deficits observed when the AP-1 function is compromised.
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Affiliation(s)
| | - Nils Bäck
- the Department of Anatomy, Faculty of Medicine, University of Helsinki, FIN-00014 Helsinki, Finland, and
| | - Megan E Duffy
- the Department of Molecular and Medical Genetics, Oregon Health and Sciences University, Portland, Oregon 97239
| | - Martina Ralle
- the Department of Molecular and Medical Genetics, Oregon Health and Sciences University, Portland, Oregon 97239
| | - Richard E Mains
- Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Betty A Eipper
- From the Departments of Molecular Biology and Biophysics and Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030,
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5
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Rehfeld JF. Do glycine-extended hormone precursors have clinical significance? INTERNATIONAL JOURNAL OF ENDOCRINE ONCOLOGY 2014. [DOI: 10.2217/ije.14.14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Half of the known peptide hormones are C-terminally amidated. Subsequent biogenesis studies have shown that the immediate precursor is a glycine-extended peptide. The clinical interest in glycine-extended hormones began in 1994, when it was suggested that glycine-extended gastrin stimulated cancer cell growth. Accompanying findings of gastrin gene expression in common cancers spurred the interest. The interest is now accompanied by skepticism, which is due to failure to demonstrate truly specific receptors for glycine-extended peptides and failure to demonstrate separate physiological and clinical effects of glycine-extended precursors for most other amidated hormones than gastrin and cholecystokinin (CCK). The idea of glycine-extended peptides as independent messengers was interesting. But clinical science has to move ahead from ideas that cannot be supported at key points after decades of research.
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6
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Yin P, Bousquet-Moore D, Annangudi SP, Southey BR, Mains RE, Eipper BA, Sweedler JV. Probing the production of amidated peptides following genetic and dietary copper manipulations. PLoS One 2011; 6:e28679. [PMID: 22194882 PMCID: PMC3241674 DOI: 10.1371/journal.pone.0028679] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 11/13/2011] [Indexed: 11/23/2022] Open
Abstract
Amidated neuropeptides play essential roles throughout the nervous and endocrine systems. Mice lacking peptidylglycine α-amidating monooxygenase (PAM), the only enzyme capable of producing amidated peptides, are not viable. In the amidation reaction, the reactant (glycine-extended peptide) is converted into a reaction intermediate (hydroxyglycine-extended peptide) by the copper-dependent peptidylglycine-α-hydroxylating monooxygenase (PHM) domain of PAM. The hydroxyglycine-extended peptide is then converted into amidated product by the peptidyl-α-hydroxyglycine α-amidating lyase (PAL) domain of PAM. PHM and PAL are stitched together in vertebrates, but separated in some invertebrates such as Drosophila and Hydra. In addition to its luminal catalytic domains, PAM includes a cytosolic domain that can enter the nucleus following release from the membrane by γ-secretase. In this work, several glycine- and hydroxyglycine-extended peptides as well as amidated peptides were qualitatively and quantitatively assessed from pituitaries of wild-type mice and mice with a single copy of the Pam gene (PAM+/−) via liquid chromatography-mass spectrometry-based methods. We provide the first evidence for the presence of a peptidyl-α-hydroxyglycine in vivo, indicating that the reaction intermediate becomes free and is not handed directly from PHM to PAL in vertebrates. Wild-type mice fed a copper deficient diet and PAM+/− mice exhibit similar behavioral deficits. While glycine-extended reaction intermediates accumulated in the PAM+/− mice and reflected dietary copper availability, amidated products were far more prevalent under the conditions examined, suggesting that the behavioral deficits observed do not simply reflect a lack of amidated peptides.
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Affiliation(s)
- Ping Yin
- Department of Chemistry, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Danielle Bousquet-Moore
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut, United States of America
| | - Suresh P. Annangudi
- Department of Chemistry, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Bruce R. Southey
- Department of Chemistry, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Richard E. Mains
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut, United States of America
| | - Betty A. Eipper
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut, United States of America
- * E-mail: (JVS); (BAE)
| | - Jonathan V. Sweedler
- Department of Chemistry, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail: (JVS); (BAE)
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7
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An Z, Chen Y, Koomen JM, Merkler DJ. A mass spectrometry-based method to screen for α-amidated peptides. Proteomics 2011; 12:173-82. [PMID: 22106059 DOI: 10.1002/pmic.201100327] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 10/26/2011] [Accepted: 11/03/2011] [Indexed: 01/23/2023]
Abstract
Amidation is a post-translational modification found at the C-terminus of ~50% of all neuropeptide hormones. Cleavage of the C(α)-N bond of a C-terminal glycine yields the α-amidated peptide in a reaction catalyzed by peptidylglycine α-amidating monooxygenase (PAM). The mass of an α-amidated peptide decreases by 58 Da relative to its precursor. The amino acid sequences of an α-amidated peptide and its precursor differ only by the C-terminal glycine meaning that the peptides exhibit similar RP-HPLC properties and tandem mass spectral (MS/MS) fragmentation patterns. Growth of cultured cells in the presence of a PAM inhibitor ensured the coexistence of α-amidated peptides and their precursors. A strategy was developed for precursor and α-amidated peptide pairing (PAPP): LC-MS/MS data of peptide extracts were scanned for peptide pairs that differed by 58 Da in mass, but had similar RP-HPLC retention times. The resulting peptide pairs were validated by checking for similar fragmentation patterns in their MS/MS data prior to identification by database searching or manual interpretation. This approach significantly reduced the number of spectra requiring interpretation, decreasing the computing time required for database searching and enabling manual interpretation of unidentified spectra. Reported here are the α-amidated peptides identified from AtT-20 cells using the PAPP method.
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Affiliation(s)
- Zhenming An
- Department of Chemistry, University of South Florida, Tampa, FL 33620-5250, USA
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8
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De M, Ciccotosto GD, Mains RE, Eipper BA. Trafficking of a secretory granule membrane protein is sensitive to copper. J Biol Chem 2007; 282:23362-71. [PMID: 17562710 DOI: 10.1074/jbc.m702891200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We explored the effect of copper availability on the synthesis and trafficking of peptidylglycine alpha-amidating monooxygenase (PAM), an essential cuproenzyme whose catalytic domains function in the lumen of peptide-containing secretory granules. Corticotrope tumor cell lines expressing integral membrane and soluble forms of PAM were depleted of copper using bathocuproinedisulfonic acid or loaded with copper by incubation with CuCl(2). Depleting cellular copper stimulates basal secretion of soluble enzyme produced by endoproteolytic cleavage of PAM in secretory granules and transit of membrane PAM though the endocytic pathway and back into secretory granules. Unlike many cuproenzymes, lack of copper does not lead to instability of PAM. Copper loading decreases cleavage of PAM in secretory granules, secretion of soluble enzyme, and the return of internalized PAM to secretory granules. The trafficking and stability of the soluble, luminal domain of PAM and truncated membrane PAM lacking a cytosolic domain are not affected by copper availability. Taken together, our data demonstrate a role for copper-sensitive cytosolic machinery in directing endocytosed membrane PAM back to secretory granules or to a degradative pathway. The response of PAM to lack of copper suggests that it facilitates copper homeostasis.
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Affiliation(s)
- Mithu De
- University of Connecticut Health Center, Farmington, Connecticut 06030-3401, USA
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9
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Czyzyk TA, Ning Y, Hsu MS, Peng B, Mains RE, Eipper BA, Pintar JE. Deletion of peptide amidation enzymatic activity leads to edema and embryonic lethality in the mouse. Dev Biol 2005; 287:301-13. [PMID: 16225857 DOI: 10.1016/j.ydbio.2005.09.001] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Revised: 08/04/2005] [Accepted: 09/06/2005] [Indexed: 11/25/2022]
Abstract
Peptidylglycine alpha-amidating monooxygenase (PAM) catalyzes the COOH-terminal amidation of peptide hormones. We previously had found high expression of PAM in several regions of the developing rodent. To determine the function of PAM during mouse embryogenesis, we produced a null mutant of the PAM gene. Homozygous mutants die in utero between e14.5 and e15.5 with severe edema that is likely due to cardiovascular deficits. These defects include thinning of the aorta and carotid arteries and are very similar to those of the recently characterized adrenomedullin (AM) gene KO despite the presence of elevated immunoreactive AM in PAM KO embryos. No peptide amidation activity was detected in PAM mutant embryos, and there was no moderation of the AM-like phenotype that could be expected if any alternative peptide amidation mechanism exists in the mouse. Despite the proposed contribution of amidated peptides to neuronal cell proliferation, no alteration in neuroblast proliferation was observed in homozygous mutant embryos prior to lethality. Mice heterozygous for the mutant PAM allele develop normally and express wildtype levels of several amidated peptides despite having one half the wildtype levels of PAM activity and PAM protein. Nonetheless, both an increase in adiposity and a mild glucose intolerance developed in aged (>10 months) heterozygous mice compared to littermate controls. Ablation of PAM thus demonstrates an essential function for this gene during mouse development, while alterations in PAM activity in the adult may underlie more subtle physiologic effects.
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Affiliation(s)
- Traci A Czyzyk
- Department of Neuroscience and Cell Biology, CABM Rm 326, UMDNJ-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA
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10
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Chew GH, Galloway LC, McIntyre NR, Schroder LA, Richards KM, Miller SA, Wright DW, Merkler DJ. Ubiquitin and ubiquitin-derived peptides as substrates for peptidylglycine alpha-amidating monooxygenase. FEBS Lett 2005; 579:4678-84. [PMID: 16098968 DOI: 10.1016/j.febslet.2005.06.089] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2005] [Revised: 06/15/2005] [Accepted: 06/18/2005] [Indexed: 12/16/2022]
Abstract
Ubiquitin (Ub) and the ubiquitin-like proteins (UBLs) mediate an array of cellular functions. These proteins contain a C-terminal glycine residue that is key to their function. Oxidative conversion of C-terminal glycine-extended prohormones to the corresponding alpha-amidated peptide is one step in the biosynthesis of bioactive peptide hormones. The enzyme catalyzing this reaction is peptidylglycine alpha-amidating monooxygenase (PAM). We report herein that Ub is a PAM substrate with a (V/K)(amidation) that is similar to other known peptide substrates. This work is significant because PAM and the UBLs co-localize to the hypothalamus and the adrenal medulla and are both over-expressed in glioblastomas.
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Affiliation(s)
- Geoffrey H Chew
- Department of Chemistry, University of South Florida, 4202 E. Fowler Ave., SCA 400, Tampa, FL 33620-5250, USA
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11
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Steveson TC, Ciccotosto GD, Ma XM, Mueller GP, Mains RE, Eipper BA. Menkes protein contributes to the function of peptidylglycine alpha-amidating monooxygenase. Endocrinology 2003; 144:188-200. [PMID: 12488345 DOI: 10.1210/en.2002-220716] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Menkes protein (ATP7A) is a P-type ATPase involved in copper uptake and homeostasis. Disturbed copper homeostasis occurs in patients with Menkes disease, an X-linked disorder characterized by mental retardation, neurodegeneration, connective tissue disorders, and early childhood death. Mutations in ATP7A result in malfunction of copper-requiring enzymes, such as tyrosinase and copper/zinc superoxide dismutase. The first step of the two-step amidation reaction carried out by peptidylglycine alpha-amidating monooxygenase (PAM) also requires copper. We used tissue from wild-type rats and mice and an ATP7A-specific antibody to determine that ATP7A is expressed at high levels in tissues expressing high levels of PAM. ATP7A is largely localized to the trans Golgi network in pituitary endocrine cells. The Atp7a mouse, bearing a mutation in the Atp7a gene, is an excellent model system for examining the consequences of ATP7A malfunction. Despite normal levels of PAM protein, levels of several amidated peptides were reduced in pituitary and brain extracts of Atp7a mice, demonstrating that PAM function is compromised when ATP7A is inactive. Based on these results, we conclude that a reduction in the ability of PAM to produce bioactive end-products involved in neuronal growth and development could contribute to many of the biological effects associated with Menkes disease.
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Affiliation(s)
- Tami C Steveson
- Department of Neuroscience,, University of Connecticut Health Center, Farmington, Connecticut 06030-3401, USA
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12
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Alam MR, Steveson TC, Johnson RC, Bäck N, Abraham B, Mains RE, Eipper BA. Signaling mediated by the cytosolic domain of peptidylglycine alpha-amidating monooxygenase. Mol Biol Cell 2001; 12:629-44. [PMID: 11251076 PMCID: PMC30969 DOI: 10.1091/mbc.12.3.629] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The luminal domains of membrane peptidylglycine alpha-amidating monooxygenase (PAM) are essential for peptide alpha-amidation, and the cytosolic domain (CD) is essential for trafficking. Overexpression of membrane PAM in corticotrope tumor cells reorganizes the actin cytoskeleton, shifts endogenous adrenocorticotropic hormone (ACTH) from mature granules localized at the tips of processes to the TGN region, and blocks regulated secretion. PAM-CD interactor proteins include a protein kinase that phosphorylates PAM (P-CIP2) and Kalirin, a Rho family GDP/GTP exchange factor. We engineered a PAM protein unable to interact with either P-CIP2 or Kalirin (PAM-1/K919R), along with PAM proteins able to interact with Kalirin but not with P-CIP2. AtT-20 cells expressing PAM-1/K919R produce fully active membrane enzyme but still exhibit regulated secretion, with ACTH-containing granules localized to process tips. Immunoelectron microscopy demonstrates accumulation of PAM and ACTH in tubular structures at the trans side of the Golgi in AtT-20 cells expressing PAM-1 but not in AtT-20 cells expressing PAM-1/K919R. The ability of PAM to interact with P-CIP2 is critical to its ability to block exit from the Golgi and affect regulated secretion. Consistent with this, mutation of its P-CIP2 phosphorylation site alters the ability of PAM to affect regulated secretion.
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Affiliation(s)
- M R Alam
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030-3401, USA
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13
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Ciccotosto GD, Hand TA, Mains RE, Eipper BA. Breeding stock-specific variation in peptidylglycine alpha-amidating monooxygenase messenger ribonucleic acid splicing in rat pituitary. Endocrinology 2000; 141:476-86. [PMID: 10650926 DOI: 10.1210/endo.141.2.7337] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Peptidylglycine alpha-amidating monooxygenase (PAM) is a bifunctional enzyme that catalyzes the carboxyl-terminal amidation of glycine-extended peptides in a two-step reaction involving a monooxygenase and a lyase. Several forms of PAM messenger RNA result from alternative splicing of the single copy PAM gene. The presence of alternately spliced exon A between the two enzymatic domains allows endoproteolytic cleavage to occur in selected tissues, generating soluble monooxygenase and membrane lyase from integral membrane PAM. While using an exon A antiserum, we made the unexpected observation that Charles River Sprague Dawley rats expressed forms of PAM containing exon A in their pituitaries, whereas Harlan Sprague Dawley rats did not. Forms of PAM containing exon A were expressed in the atrium and hypothalamus of both types of Sprague Dawley rat, although in different proportions. PAM transmembrane domain splicing also differed between rat breeders, and full-length PAM-1 was not prevalent in the anterior pituitary of either type of rat. Despite striking differences in PAM splicing, no differences in levels of monooxygenase or lyase activity were observed in tissue or serum samples. The splicing patterns of other alternatively spliced genes, pituitary adenylate cyclase-activating polypeptide receptor type 1 and cardiac troponin T, did not vary with rat breeder. Strain-specific variations in the splicing of transcripts such as PAM must be taken into account in analyzing the resultant proteins, and knowledge of these differences should identify variations with functional significance.
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Affiliation(s)
- G D Ciccotosto
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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14
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Mains RE, Alam MR, Johnson RC, Darlington DN, Bäck N, Hand TA, Eipper BA. Kalirin, a multifunctional PAM COOH-terminal domain interactor protein, affects cytoskeletal organization and ACTH secretion from AtT-20 cells. J Biol Chem 1999; 274:2929-37. [PMID: 9915831 DOI: 10.1074/jbc.274.5.2929] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The production and regulated secretion of bioactive peptides require a series of lumenal enzymes to convert inactive precursors into bioactive peptides plus several cytosolic proteins to govern granule formation, maturation, translocation, and exocytosis. Peptidylglycine alpha-amidating monooxygenase (PAM), an enzyme essential for biosynthesis of many peptides, is an integral membrane protein with trafficking information in both its lumenal and cytosolic domains. Kalirin, a PAM cytosolic domain interactor protein with spectrin-like repeats and GDP/GTP exchange factor activity for Rac1, is expressed with PAM in neurons but is not expressed in the anterior pituitary or AtT-20 corticotrope cells. Expression of Kalirin alters the cytoskeletal organization of Chinese hamster ovary and AtT-20 cells expressing membrane PAM. Expression of membrane PAM also alters cytoskeletal organization, demonstrating the presence of endogenous proteins that can mediate this effect. Significant amounts of both PAM and Kalirin fractionate with cytoskeletal elements. Since cytoskeletal organization is critical for exocytosis, constitutive-like and regulated secretions were evaluated. Whereas the constitutive-like secretion of adrenocorticotropic hormone (ACTH) is increased by expression of membrane PAM, regulated secretion is eliminated. Expression of Kalirin in AtT-20 cells expressing membrane PAM restores stimulated secretion of ACTH. Thus, Kalirin or its homologue may be essential for regulated secretion, and the PAM-Kalirin interaction may coordinate intragranular with cytosolic events.
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Affiliation(s)
- R E Mains
- Departments of Neuroscience and Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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15
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Bruhn TO, Rondeel JM, Jackson IM. Thyrotropin-releasing hormone gene expression in the anterior pituitary. IV. Evidence for paracrine and autocrine regulation. Endocrinology 1998; 139:3416-22. [PMID: 9681491 DOI: 10.1210/endo.139.8.6146] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Disulfiram (Dis), an inhibitor of peptidyl-glycine alpha-amidating monooxygenase, the enzyme responsible for the production of alpha-amidated peptides from their immediate, glycine-extended precursors was used to investigate the paracrine effects of TRH on anterior pituitary (AP) hormone secretion. It reduces the production of TRH without directly affecting the classical pituitary hormones, none of which is amidated. Dis (8 microM) decreased the accumulation of TRH accompanied by an equimolar increase in TRH-Gly levels, indicating that pro-TRH biosynthesis persisted. TRH and TSH release into the medium was significantly lowered, whereas other pituitary hormones were unaffected. In contrast, dexamethasone (10 nM), which up-regulates TRH gene expression in this system, increased TRH (+89.5%) and TSH (+61.3%) secretion. The combination of dexamethasone and Dis further diminished the release of TRH (-73%) and TSH (-40.3%) observed with Dis alone, indicating that TRH synthesized within the AP regulates TSH secretion. Dis significantly elevated prepro-TRH (25-50) and pro-TRH messenger RNA levels, suggesting that reduced TRH formation leads to increased pro-TRH biosynthesis and that TRH regulates its own secretion. Thus, TRH synthesized by cultured AP cells not only stimulates TSH release through a paracrine effect, but has a negative feedback on its own biosynthesis by an autocrine mechanism.
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Affiliation(s)
- T O Bruhn
- Department of Medicine, Brown University/Rhode Island Hospital, Providence 02903, USA
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16
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Use of endoproteases to identify catalytic domains, linker regions, and functional interactions in soluble peptidylglycine alpha-amidating monooxygenase. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)98406-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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17
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Aspartimide formation in the joining peptide sequence of porcine and mouse pro-opiomelanocortin. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)54036-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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18
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Zhou A, Bloomquist B, Mains R. The prohormone convertases PC1 and PC2 mediate distinct endoproteolytic cleavages in a strict temporal order during proopiomelanocortin biosynthetic processing. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53918-1] [Citation(s) in RCA: 191] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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19
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Castro MG, Lowry PJ, Lowenstein PR. Antibodies to neuropeptide precursors expressed as fusion proteins in E. coli. Their use to examine neuropeptide biosynthetic pathways, intracellular trafficking and physiological activities. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1992; 24:847-60. [PMID: 1612176 DOI: 10.1016/0020-711x(92)90089-j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- M G Castro
- Department of Biochemistry and Physiology, School of Animal and Microbial Sciences, University of Reading, England
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20
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Eipper B, Green C, Campbell T, Stoffers D, Keutmann H, Mains R, Ouafik L. Alternative splicing and endoproteolytic processing generate tissue-specific forms of pituitary peptidylglycine alpha-amidating monooxygenase (PAM). J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50625-1] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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21
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Affiliation(s)
- L Hilsted
- Department of Clinical Chemistry, State University Hospital (Rigshospitalet), Copenhagen, Denmark
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22
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Takeuchi T, Dickinson C, Taylor I, Yamada T. Expression of human pancreatic polypeptide in heterologous cell lines. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(19)47388-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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23
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Fenger M. Processing of pro-opiomelanocortin-derived amidated joining peptide and glycine-extended precursor in monkey pituitary. Neurosci Lett 1991; 124:190-4. [PMID: 2067719 DOI: 10.1016/0304-3940(91)90091-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The molecular forms of proopiomelanocortin (POMC) derived amidated and C-terminal glycine-extended joining peptide from monkey (Macaca mulatta) pituitary were determined. The predominant forms of joining peptide found were the low molecular peptides POMC(76-105) and POMC(76-106), respectively. Significant amounts of N-terminally truncated POMC(78-105) and POMC(78-106) were also detected in the posterior-intermediate lobe. No N-terminal extended forms were detected. The relative amount of amidated joining peptide to total joining peptide was 6-35%. It is concluded that not only is the primary sequence of monkey and human POMC extremely conserved, but also the processing patterns are similar. The monkey therefore serves as a suitable model for studying regulation of the processing of POMC and the hypothalamus-pituitary-adrenal axis in man.
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Affiliation(s)
- M Fenger
- Mental Health Research Institute, University of Michigan, Ann Arbor 48109
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24
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Assays for Biosynthesis of Thyrotropin-Releasing Hormone. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/b978-0-12-185261-0.50009-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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25
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Dickerson IM, Dixon JE, Mains RE. Biosynthesis and posttranslational processing of site-directed endoproteolytic cleavage mutants of pro-neuropeptide Y in mouse pituitary cells. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39822-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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26
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Bjartell A, Fenger M, Ekman R, Sundler F. Amidated joining peptide in the human pituitary, gut, adrenal gland and bronchial carcinoids. Immunocytochemical and immunochemical evidence. Peptides 1990; 11:149-61. [PMID: 2188229 DOI: 10.1016/0196-9781(90)90124-n] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The distribution of the proopiomelanocortin-derivated amidated joining peptide (JP-N) was examined in the human pituitary gland, adrenal gland, gut and in three bronchial carcinoids. Double immunostaining showed coexistence of immunoreactive JP-N and other proopiomelanocortin derivatives, e.g., ACTH, beta-endorphin, Pro-tau-MSH, in the pituitary gland and adrenal medulla. The JP-N immunoreactive cells in the adrenal medulla were identified as a subpopulation of adrenaline-producing cells by means of an antiserum against phenylethanolamine N-methyltransferase. In the gut immunoreactive JP-N was costored with somatostatin in endocrine cells. Using radioimmunoassay, JP-N was found in higher concentrations than ACTH and alpha-MSH in the gut but not in the adrenal gland. Gel chromatography of gastric antrum and adrenal gland extracts showed three and two dominating components of immunoreactive JP-N, respectively, but under reduced conditions most of the immunoreactive material appeared as of low molecular weight in both extracts. In conclusion, immunoreactive JP-N is a major product from the processing of proopiomelanocortin in human extrapituitary tissues. The molecular forms of immunoreactive JP-N correspond to previous findings in the human pituitary gland.
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Affiliation(s)
- A Bjartell
- Department of Medical Cell Research, Lund, Sweden
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27
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Birnbaum RS, Bertelsen AH, Roos BA. Glucocorticoid regulation of amidating enzyme in a neoplastic C-cell line. Mol Cell Endocrinol 1989; 61:109-16. [PMID: 2744211 DOI: 10.1016/0303-7207(89)90194-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Posttranslational carboxyl-terminal amidation of many peptides is accomplished by peptidylglycine alpha-amidating monooxygenase. We have previously demonstrated that glucocorticoids stimulate production of amidated products by the CA-77 rat medullary thyroid carcinoma cell line. The present investigation was undertaken to determine whether amidation enzyme activity changes in parallel. Enzyme activity, similar to that found in other tissues, was readily detected in cell extracts and conditioned cultured medium. Stimulation with the calcitonin secretagogue calcium increased secretion of enzyme activity and lowered cell extract activity. Treatment of cultures with dexamethasone, but no other steroid, decreased by 50-70% the basal amidation enzyme activity secreted. There was no associated change in cellular activity. The decrease in medium activity was partially reversible and steroid-dose dependent. The glucocorticoid-induced change in medium activity was due to a decreased Vm. These experiments demonstrate that the alpha-amidating activity of the CA-77 cells can be hormonally regulated.
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Affiliation(s)
- R S Birnbaum
- Research Service and Geriatric Research, Veterans Administration Medical Center, Tacoma, WA 98493
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28
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Mains RE, May V. The role of a low pH intracellular compartment in the processing, storage, and secretion of ACTH and endorphin. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68581-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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29
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Abstract
Peptidyl-glycine alpha-amidation enzyme activity has been measured in 36 nuclei or areas in the rat CNS and pituitary using D-Tyr-Phe-Gly as the substrate. The distribution of this enzyme is highly uneven, with highest activity levels (greater than 30 pmol/mg of protein/h) in hypothalamic nuclei, substantia grisea centralis, and nucleus ruber; moderate activity levels (10-30 pmol/mg of protein/h) in globus pallidus, septum, midbrain, pons, medulla oblongata, and cervical spinal cord; and low activity levels (1-10 pmol/mg of protein/h) in other telencephalic and thalamic structures. Almost no alpha-amidation activity (less than 0.5 pmol/mg of protein/h) was detected in cerebellar cortex. The Km values in several brain regions are of the same order.
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Affiliation(s)
- F Meng
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences
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30
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Fenger M. Pro-opiomelanocortin-derived peptides in the pig pituitary: alpha- and gamma 1-melanocyte-stimulating hormones and their glycine-extended forms. REGULATORY PEPTIDES 1988; 20:345-57. [PMID: 2835797 DOI: 10.1016/0167-0115(88)90069-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Pro-opiomelanocortin (POMC)-related peptides in extracts of anterior and neurointermediate pituitary lobes from pigs were characterized by gel chromatography, reversed-phase chromatography and radioimmunoassays. The peptide content was ca. 3-fold greater in the anterior lobe compared to the neurointermediate lobe (19.8 nmol POMC/anterior lobe vs 7.0 nmol/neurointermediate lobe). In the neurointermediate lobe 93% of POMC was processed to alpha-melanocyte-stimulating hormone (alpha-MSH) and analogs exclusively of low molecular weight. Most of the remaining adrenocorticotropic hormone (ACTH)-related material consisted of the glycine-extended intermediate ACTH-(1-14) and analogs. In contrast only one fourth to one third of the N-terminal part of POMC (N-POMC) was processed to amidated gamma-MSH and its C-terminal glycine-extended precursor. The relative amount of amidated gamma-MSH was the same as alpha-MSH and analogs (94%). However, more than 95% of these peptides were of high molecular weight. In the anterior lobe 2.3% of N-POMC was processed and 94% was amidated gamma-MSH of only high molecular weight. These results show that gamma-MSH and alpha-MSH are amidated to the same extent and that gamma 1-MSH and gamma 2-MSH immunoreactivity are present in both the anterior lobe and the neurointermediate lobe. The results suggest that the production of amidated peptides is not regulated by the amidation process itself but at an earlier step (e.g. at the proteolytic cleavage).
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Affiliation(s)
- M Fenger
- Department of Clinical Chemistry, University of Copenhagen, Rigshospitalet, Denmark
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31
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CULLEN EI, MAINS RE. Biosynthesis of Joining Peptide from Pro-ACTH/Endorphin. Ann N Y Acad Sci 1987. [DOI: 10.1111/j.1749-6632.1987.tb24984.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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32
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Abstract
There are many events in the posttranslational processing of bioactive peptides that occur in secretory granules and not to any great extent in other cellular organelles and that do not appear as modifications of the structure of many conventional neurotransmitters. In addition, at least two very important steps are unique to peptide-containing granules: (1) the peptides must begin their trek to the secretory granule in the RER as a larger precursor, rather than being taken up as a finished or nearly finished product into a mature granule; (2) there is at least one crucial sorting step on the way from the RER to the secretory granule that must occur faithfully before the peptide correctly appears in the granule. As for small molecules such as the catecholamines, the posttranslational processing enzymes and any required cofactors must also be put into the granules if the final events of processing are to occur with fidelity. Many of the posttranslational processing enzymes are only beginning to be identified. It is clear from these studies on purified PAM and peptide alpha-amidation as it occurs in cells that correlating test tube studies with the functioning of secretory granules is a worthwhile, if difficult, pursuit. The unique milieu inside the granule is difficult to mimic in a test tube. Transfection of peptide-producing cells with cDNAs encoding precursors with specific alterations in processing sites offers perhaps the best way to interface the studies of secretory granules and the posttranslational processing enzymes that mediate those functions.
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33
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Mains RE, Park LP, Eipper BA. Inhibition of peptide amidation by disulfiram and diethyldithiocarbamate. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)67182-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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34
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