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Harno E, Gali Ramamoorthy T, Coll AP, White A. POMC: The Physiological Power of Hormone Processing. Physiol Rev 2019; 98:2381-2430. [PMID: 30156493 DOI: 10.1152/physrev.00024.2017] [Citation(s) in RCA: 112] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Pro-opiomelanocortin (POMC) is the archetypal polypeptide precursor of hormones and neuropeptides. In this review, we examine the variability in the individual peptides produced in different tissues and the impact of the simultaneous presence of their precursors or fragments. We also discuss the problems inherent in accurately measuring which of the precursors and their derived peptides are present in biological samples. We address how not being able to measure all the combinations of precursors and fragments quantitatively has affected our understanding of the pathophysiology associated with POMC processing. To understand how different ratios of peptides arise, we describe the role of the pro-hormone convertases (PCs) and their tissue specificities and consider the cellular processing pathways which enable regulated secretion of different peptides that play crucial roles in integrating a range of vital physiological functions. In the pituitary, correct processing of POMC peptides is essential to maintain the hypothalamic-pituitary-adrenal axis, and this processing can be disrupted in POMC-expressing tumors. In hypothalamic neurons expressing POMC, abnormalities in processing critically impact on the regulation of appetite, energy homeostasis, and body composition. More work is needed to understand whether expression of the POMC gene in a tissue equates to release of bioactive peptides. We suggest that this comprehensive view of POMC processing, with a focus on gaining a better understanding of the combination of peptides produced and their relative bioactivity, is a necessity for all involved in studying this fascinating physiological regulatory phenomenon.
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Affiliation(s)
- Erika Harno
- Division of Diabetes, Endocrinology and Gastrointestinal Sciences, Faculty of Biology, Medicine and Health, University of Manchester , Manchester , United Kingdom ; and MRC Metabolic Diseases Unit, Wellcome Trust-MRC Institute of Metabolic Science , Cambridge , United Kingdom
| | - Thanuja Gali Ramamoorthy
- Division of Diabetes, Endocrinology and Gastrointestinal Sciences, Faculty of Biology, Medicine and Health, University of Manchester , Manchester , United Kingdom ; and MRC Metabolic Diseases Unit, Wellcome Trust-MRC Institute of Metabolic Science , Cambridge , United Kingdom
| | - Anthony P Coll
- Division of Diabetes, Endocrinology and Gastrointestinal Sciences, Faculty of Biology, Medicine and Health, University of Manchester , Manchester , United Kingdom ; and MRC Metabolic Diseases Unit, Wellcome Trust-MRC Institute of Metabolic Science , Cambridge , United Kingdom
| | - Anne White
- Division of Diabetes, Endocrinology and Gastrointestinal Sciences, Faculty of Biology, Medicine and Health, University of Manchester , Manchester , United Kingdom ; and MRC Metabolic Diseases Unit, Wellcome Trust-MRC Institute of Metabolic Science , Cambridge , United Kingdom
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Wittmann G, Lechan RM. Prss56 expression in the rodent hypothalamus: Inverse correlation with pro-opiomelanocortin suggests oscillatory gene expression in adult rat tanycytes. J Comp Neurol 2018; 526:2444-2461. [PMID: 30242838 DOI: 10.1002/cne.24504] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 06/27/2018] [Accepted: 07/12/2018] [Indexed: 11/11/2022]
Abstract
We recently reported that the number of hypothalamic tanycytes expressing pro-opiomelanocortin (Pomc) is highly variable among brains of adult rats. While its cause and significance remain unknown, identifying other variably expressed genes in tanycytes may help understand this curious phenomenon. In this in situ hybridization study, we report that the Prss56 gene, which encodes a trypsin-like serine protease and is expressed in neural stem/progenitor cells, shows a similarly variable mRNA expression in tanycytes of adult rats and correlates inversely with tanycyte Pomc mRNA. Prss56 was expressed in α1, β1, subsets of α2, and some median eminence γ tanycytes, but virtually absent from β2 tanycytes. Prss56 was also expressed in vimentin positive tanycyte-like cells in the parenchyma of the ventromedial and arcuate nuclei, and in thyrotropin beta subunit-expressing cells of the pars tuberalis of the pituitary. In contrast to adults, Prss56 expression was uniformly high in tanycytes in adolescent rats. In mice, Prss56-expressing tanycytes and parenchymal cells were also observed but fewer in number and without significant variations. The results identify Prss56 as a second gene that is expressed variably in tanycytes of adult rats. We propose that the variable, inversely correlating expression of Prss56 and Pomc reflect periodically oscillating gene expression in tanycytes rather than stable expression levels that vary between individual rats. A possible functional link between Prss56 and POMC, and Prss56 as a potential marker for migrating tanycytes are discussed.
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Affiliation(s)
- Gábor Wittmann
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tupper Research Institute, Tufts Medical Center, Boston, Massachusetts
| | - Ronald M Lechan
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tupper Research Institute, Tufts Medical Center, Boston, Massachusetts.,Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts
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Bicknell AB. 60 YEARS OF POMC: N-terminal POMC peptides and adrenal growth. J Mol Endocrinol 2016; 56:T39-48. [PMID: 26759392 DOI: 10.1530/jme-15-0269] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 01/12/2016] [Indexed: 11/08/2022]
Abstract
The peptide hormones contained within the sequence of proopiomelanocortin (POMC) have diverse roles ranging from pigmentation to regulation of adrenal function to control of our appetite. It is generally acknowledged to be the archetypal hormone precursor, and as its biology has been unravelled, so too have many of the basic principles of hormone biosynthesis and processing. This short review focuses on one group of its peptide products, namely, those derived from the N-terminal of POMC and their role in the regulation of adrenal growth. From a historical and a personal perspective, it describes how their role in regulating proliferation of the adrenal cortex was identified and also highlights the key questions that remain to be answered.
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Affiliation(s)
- Andrew B Bicknell
- School of Biological SciencesUniversity of Reading, Whiteknights, Reading, UK
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Lotfi CFP, de Mendonca POR. Comparative Effect of ACTH and Related Peptides on Proliferation and Growth of Rat Adrenal Gland. Front Endocrinol (Lausanne) 2016; 7:39. [PMID: 27242663 PMCID: PMC4860745 DOI: 10.3389/fendo.2016.00039] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Accepted: 04/25/2016] [Indexed: 11/30/2022] Open
Abstract
Pro-opiomelanocortin (POMC) is a polypeptide precursor known to yield biologically active peptides related to a range of functions. These active peptides include the adrenocorticotropic hormone (ACTH), which is essential for maintenance of adrenal growth and steroidogenesis, and the alpha-melanocyte stimulation hormone, which plays a key role in energy homeostasis. However, the role of the highly conserved N-terminal region of POMC peptide fragments has begun to be unraveled only recently. Here, we review the cascade of events involved in regulation of proliferation and growth of murine adrenal cortex triggered by ACTH and other POMC-derived peptides. Key findings regarding signaling pathways and modulation of genes and proteins required for the regulation of adrenal growth are summarized. We have outlined the known mechanisms as well as future challenges for research on the regulation of adrenal proliferation and growth triggered by these peptides.
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Affiliation(s)
- Claudimara Ferini Pacicco Lotfi
- Department of Anatomy, Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
- *Correspondence: Claudimara Ferini Pacicco Lotfi,
| | - Pedro O. R. de Mendonca
- Department of Anatomy, Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
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Bicknell KA, Harmer SC, Yiangson S, Lockwood W, Bicknell AB. Lys-gamma3-MSH: a global regulator of hormone sensitive lipase activity? Mol Cell Endocrinol 2009; 300:71-6. [PMID: 18977407 DOI: 10.1016/j.mce.2008.09.032] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 09/23/2008] [Accepted: 09/23/2008] [Indexed: 11/18/2022]
Abstract
Gamma-melanocyte stimulating hormone (gamma-MSH) is a peptide derived from the ACTH precursor, pro-opiomelanocortin (POMC), and belongs to a family of peptides called the melanocortins that also comprises alpha- and beta-MSH. Although conserved in tetrapods, the biological role of gamma-MSH remains largely undefined. It has been demonstrated previously that gamma-MSH is involved in the regulating the activity of hormone sensitive lipase (HSL) activity in the adrenal and more recently, in the adipocyte. It has been shown also to have effects on the cardiovascular and renal systems. This short review will provide a brief overview of the role of gamma-MSH in the adrenal and the more recent report that it can also regulate HSL function in the adipocyte. We also present some preliminary data purporting a direct role for Lys-gamma(3)-MSH in the regulation of HSL phosphorylation in the heart. Taken together these data suggest that gamma-MSH peptides might play a more widespread role in lipid and cholesterol utilization.
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Affiliation(s)
- Katrina A Bicknell
- School of Pharmacy, The University of Reading, Whiteknights, PO Box 228, Reading, Berkshire, RG6 6AJ, UK
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Harmer SC, Bicknell AB. Role of gamma-MSH peptides in the regulation of adrenal steroidogenesis. Peptides 2005; 26:1944-51. [PMID: 15985307 DOI: 10.1016/j.peptides.2004.11.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2004] [Accepted: 11/04/2004] [Indexed: 11/21/2022]
Abstract
Alpha-, beta- and gamma-melanocyte stimulating hormones (MSHs) are peptides derived from the ACTH precursor, pro-opiomelanocortin. All three peptides have been highly conserved throughout evolution but their exact biological function in mammals is still largely obscure. In recent years, there has been a surge of interest in alpha-MSH and its role in the regulation of feeding. Gamma-MSH by contrast has been shown to be involved in the regulation of adrenal steroidogenesis and also has effects on the cardiovascular and renal systems. This review will provide an overview of the role that gamma-MSH peptides play in the regulation of adrenal steroidogenesis.
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Affiliation(s)
- Stephen C Harmer
- School of Animal and Microbial Sciences, The University of Reading, Whiteknights, P.O. Box 228, Reading, Berkshire RG6 6AJ, UK
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Morano MI, de Antueno RJ, Niedfeld G, Estivariz FE. Neuroendocrine alterations in nude mice with a human lung carcinoma producing pro-opiomelanocortin, corticotrophin-releasing hormone and arginine vasopressin. Clin Endocrinol (Oxf) 1990; 32:349-62. [PMID: 2160874 DOI: 10.1111/j.1365-2265.1990.tb00876.x] [Citation(s) in RCA: 5] [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
A mucoepidermoid carcinoma of the lung (ICD classification 8430/3) resected from a patient with no clinical signs of pituitary-adrenal alterations was transplanted into 2-month-old athymic nu/nu nude mice, with the purpose of studying the effects exerted by the human tumour on the host hypothalamo-pituitary-adrenal axis. The tumour produces peptides derived from different regions of pro-opiomelanocortin (POMC: ACTH, 7.6 +/- 0.7; N-terminal POMC, 6.6 +/- 0.6; beta-LPH/endorphin, 7.3 +/- 0.7; and alpha-MSH;3.8 +/- 0.5 pmol/g wet tissue) and the neuropeptides corticotrophin-releasing hormone and arginine vasopressin (CRH: 3.6 +/- 0.4 and AVP: 1.1 +/- 0.2 pmol/g wet tissue). Immunohistochemical staining of consecutive sections of the tumour indicated that staining of tumour cells for the different peptides was not uniform and although some cells co-stained with CRH and AVP, POMC-positive cells appeared to be distinct from CRH and AVP cells. Tumour extracts were chromatographed on Sephadex G-75 and fractions monitored for POMC-derived peptides. A single peak with characteristics of alpha-MSH was detected. The ACTH, N-POMC and beta-LPH/endorphin radioimmunoassays (RIA) detected a peak at large molecular weight, eluting at the position expected for POMC. These RIA systems also revealed an ACTH(1-39) peak and another peak which probably correspond to 13 kDa ACTH, a peak eluting at the position of hN-POMC(1-48), a beta-LPH-like peak, and a smaller sized peak which may represent alpha- or gamma-endorphin. The ACTH, N-POMC and beta-LPH/endorphin contents of anterior lobe (AL) extracts, but not neutrointermediate lobe (NIL) extracts, showed a striking decrease in tumour-bearing (TB) nude mice. However, while no difference was seen in the alpha-MSH content of AL extract between TB and control (C) nude mice, it decreased in NIL extracts of TB animals. The contents of CRH and AVP in stalk-median eminence extracts of TB nude mice was significantly lower than that of C nude mice. Basal plasma corticosteroids were raised in TB nude mice at levels comparable to those in stressed C nude mice, and although adrenal weights did not vary between TB and C nude mice, morphological changes indicating hypertrophy were found in the adrenal glands of the host animals. It was concluded that the tumour dramatically alters the hypothalamo-pituitary-adrenal axis of the host, and that it may be a useful model for studying tumour-host interactions in ectopic hormone-producing tumours.
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Affiliation(s)
- M I Morano
- Centro de Estudios Endocrinos (CEEN), Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Argentina
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Pedersen RC, Brownie AC. Gamma 3-melanotropin promotes mitochondrial cholesterol accumulation in the rat adrenal cortex. Mol Cell Endocrinol 1987; 50:149-56. [PMID: 3582725 DOI: 10.1016/0303-7207(87)90087-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Gamma 3-melanotropin (gamma 3-MSH) facilitates a rapid, dose-dependent, and cycloheximide-insensitive increase in the concentration of mitochondrial free cholesterol in the adrenals of hypophysectomized rats. Physiological concentrations of various synthetic and native preparations of gamma 3-MSH are potent, while gamma-MSH is not. This cholesterol accumulation coincides with the activation of cholesteryl ester hydrolysis by gamma 3-MSH, while the rates of cholesterol esterification and of mitochondrial cholesterol side-chain cleavage are unaffected. Conversely, ACTH inhibits cholesterol ester esterification. Therefore, gamma 3-MSH and ACTH together may coordinate a substantial shift in the set-point of cholesteryl ester in equilibrium cholesterol cycling toward the right. Because ACTH also activates cholesterol side-chain cleavage, this coordinate effect on the flux of cholesterol substrate is manifest as a potentiation of corticosteroidogenesis by gamma 3-MSH. These data extend our previous studies demonstrating that pro-gamma-MSH polypeptides have an endocrine influence on the rat adrenal cortex.
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Bennett HP. Biosynthetic fate of the amino-terminal fragment of pro-opiomelanocortin within the intermediate lobe of the mouse pituitary. Peptides 1986; 7:615-22. [PMID: 3763437 DOI: 10.1016/0196-9781(86)90036-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
All the biosynthetic derivatives of pro-opiomelanocortin (POMC) were purified from an extract of 300 mouse neurointermediate pituitaries. Inspection of the amino acid composition of these peptides indicated that cleavage at all available dibasic processing sites within POMC was essentially complete except for -Arg49-Lys50- within the 1 to 74 amino-terminal sequence. Only about 50% of the 1 to 74 fragment was processed to the 1 to 49 sequence and Lys1 gamma 3MSH (i.e., the 50 to 74 sequence). The existence of these derivatives of the 1 to 74 fragment was confirmed by pulse-labelling explant cultures of mouse neurointermediate pituitaries with tritiated amino acids. Pulse/chase biosynthetic experiments indicated that the cleavage of the 1 to 74 sequence takes place 3 to 6 hours post-translation. This time course of biosynthesis suggests that the cleavage of the 1 to 74 sequence is a secretory granule event. Time course studies revealed that the minimum time required for newly synthesized derivatives of POMC to emerge from the intermediate lobe tissue was approximately 3 hours.
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Estivariz FE, Iturriza FC. An investigation on pro-opiomelanocortin and processed peptides from the teleost fish Prochilodus platensis. Peptides 1985; 6:817-24. [PMID: 3001665 DOI: 10.1016/0196-9781(85)90307-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Acid extracts of carefully dissected proadenohypophysis (PA) and metaadenohypophysis (MA) of the teleost Prochilodus platensis were subjected to chromatography in Sephadex G-50 after which several pro-opiomelanocortin (POMC) peptides were detected by means of three heterologous RIA systems: alpha-MSH, ACTH and beta-endorphin. Parallelism among extracts displacement curves ranged from 26% to 95% of those of the standard curves for the different systems employed. In PA chromatograms, peaks of ACTH immunoreactivity (IR) were detected at the positions of 30 kilodalton (K), 20K, 9K, a large 4.5K peak and 2K. Only one peak of beta-endorphin IR was detected at 30K. In MA chromatograms, ACTH IR detected similar peaks as in PA runs, but 4.5K peak was much smaller, whereas a large 2K peak roughly coincided with all alpha-MSH detected in the chromatograms. beta-Endorphin IR was detected mainly as a large peak coinciding with synthetic beta-endorphin in MA runs. Bioactivity was detected in both PA and MA 4.5K ACTH peaks, whereas little activity could be demonstrated associated with the 30K, 20K and 9K ACTH IR peaks. Prochilodus PAs and MAs were incubated with tritiated aminoacids and the extracts immunoprecipitated with ACTH, beta-endorphin and N-terminal POMC (N-POMC) antisera. The dissociated complexes were run in SDS polyacrylamide slab gel electrophoresis. The tritiated bands detected confirmed the results obtained with Sephadex chromatography. N-POMC immunoprecipitated peptides were located at 28K, 18K and 9K positions. The first two probably accounted for POMC and the N-POMC/ACTH intermediate respectively; the third corresponded to the mammalian 1-76N-POMC.(ABSTRACT TRUNCATED AT 250 WORDS)
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Jackson S, Kiser S, Corder R, Lowry PJ. Pro-opiocortin peptides in rat cerebrospinal fluid. REGULATORY PEPTIDES 1985; 11:159-71. [PMID: 2994177 DOI: 10.1016/0167-0115(85)90076-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Cerebrospinal fluid (CSF) taken from rats implanted with chronic cisternal cannulae was subjected to gel filtration chromatography on Sephadex G-50. Fractions were monitored using radioimmunoassays for N-terminal pro-opiocortin (N-POC), gamma 3-melanotropin (gamma 3-MSH), C-terminal adrenocorticotropin (C-ACTH), alpha-endorphin, beta-endorphin, gamma-lipotropin (gamma-LPH) and alpha-MSH. Two peaks which corresponded in elution position to rat N-POC (1-74) and gamma 3-MSH were detected. The major C-ACTH-immunoreactive (IR) peak was found to correspond to 14k ACTH. While no alpha-endorphin immunoreactivity was detected in rat CSF, three beta-endorphin-IR peaks were identified in positions expected for beta-LPH, beta-endorphin (1-31) and beta-endorphin (1-27), as well as a major peak of activity with the elution characteristics and cross-reactivity of rat gamma-LPH. HPLC of the alpha-MSH-IR material in rat CSF revealed the presence of a major peak of immunoreactivity whose retention time did not correspond to the known oxidised and reduced forms of alpha-MSH and its desacetylated and diacetylated derivatives. The identity of this peak is unknown.
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Alfano J, Dressler LG, Brownie AC. Immunoreactive ACTH and gamma-MSH in rat plasma during early stages of adrenal regeneration. THE AMERICAN JOURNAL OF PHYSIOLOGY 1985; 248:E471-4. [PMID: 2984942 DOI: 10.1152/ajpendo.1985.248.4.e471] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Recent evidence suggests that in addition to ACTH the pro-gamma-melanotropins play a role in controlling both the steroidogenic activity and growth of the adrenal cortex. By using the regenerating gland as a model for rapid adrenal growth, studies were carried out to monitor plasma ACTH and pro-gamma-melanotropins during the acute phase following adrenal enucleation. Adrenal enucleated rats (experimental group) were uninephroadrenalectomized; controls were uninephrectomized or uninephroadrenalectomized. At intervals up to 96 h after surgery, animals from each of the three groups were killed under quiescent conditions at the low and high points of their circadian rhythm. The plasma concentrations of both ACTH and 11 K gamma-melanocyte-stimulating hormone (MSH) in the adrenal enucleated rats were markedly elevated as compared with either control group at each time point monitored. However, there were no significant differences in plasma ACTH or 11 K gamma-MSH between the two control groups, and the levels of plasma 6 K gamma-MSH remained unchanged in all three groups throughout the experiment. These data are consistent with a role for pro-gamma-melanotropins in adrenal regeneration.
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Bennett HP. Isolation and characterization of the 1 to 49 amino-terminal sequence of pro-opiomelanocortin from bovine posterior pituitaries. Biochem Biophys Res Commun 1984; 125:229-36. [PMID: 6391486 DOI: 10.1016/s0006-291x(84)80358-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
An amino-terminal fragment of pro-opiomelanocortin (POMC) has been isolated from bovine intermediate pituitaries by reversed-phase high-performance liquid chromatography. Peptide mapping and amino acid analysis indicated that the primary sequence corresponds exactly to that predicted by cDNA techniques for the first 49 residues of POMC including the presence of four cysteine residues. This peptide is almost certainly generated together with the gamma-melanotropins during the biosynthetic processing of the 16K amino-terminal fragment of bovine POMC. Careful analysis of the fragments resulting from V8 protease and trypsin digestion has permitted assignment of cystine bridges between residues 2 and 24 and between residues 8 and 20.
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Abstract
Corticotropin (ACTH) is biosynthesized in the human pituitary gland as a long polypeptide precursor (pro-opiocortin) of some 240 residues. When ACTH is secreted in response to stress, the peptides derived from the rest of this precursor, pro-gamma-melanotropin (gamma-MSH) and beta-lipotropin (beta-LPH), are also secreted (Fig. 1). This article will describe the search for a biological significance for this phenomenon.
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