Comparison of Rat Anterior and Intermediate Pituitary in Tissue Culture: Corticotropin (ACTH) and β‐Endorphin

Mains, Richard E.; Eipper, Betty A.

doi:10.1002/9780470720646.ch4

Cited by 10 publications

(3 citation statements)

References 42 publications

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“…In contrast, rats and mice have a pars intermedia, comprised primarily of melanotrophs. Processing of POMC in the pars intermedia is similar to that in the hypothalamus, and this produces ␣-MSH and CLIP, rather than ACTH (233). This suggests that these smaller peptides are released into the circulation and must be in high concentrations in the blood of rodents.…”

Section: ␣-Msh From the Pars Intermedia Of The Pituitary In Rodentsmentioning

confidence: 99%

POMC: The Physiological Power of Hormone Processing

Harno

Ramamoorthy

Coll

et al. 2018

Physiological Reviews

155

120

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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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Section: ␣-Msh From the Pars Intermedia Of The Pituitary In Rodentsmentioning

confidence: 99%

POMC: The Physiological Power of Hormone Processing

Harno

Ramamoorthy

Coll

et al. 2018

Physiological Reviews

155

120

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“…In these cells, processing of POMC results in the generation of pro‐γ‐MSH, ACTH and β‐LPH, with little processing to the smaller peptides. This pattern of processing also occurs in the anterior pituitary (27–29), although a significant proportion of the β‐LPH is further cleaved to β‐endorphin (30, 31). There is some evidence to suggest that, in the rat and the sheep, a proportion of the ACTH is cleaved to α‐MSH and CLIP.…”

Section: Anterior Lobementioning

confidence: 99%

“…Processing of POMC in the intermediate lobe is more extensive with further cleavage of the peptides produced in the anterior lobe. ACTH is cleaved to α‐MSH and CLIP whereas β‐LPH is virtually completely processed to β‐endorphin and γ‐LPH (28, 32). β‐endorphin 1‐31 is cleaved at the C‐terminus to give β‐endorphin 1‐27 , β‐endorphin 1‐26 and a dipeptide glycylglutamine (31).…”

Section: Intermediate Lobementioning

confidence: 99%

The Tissue‐Specific Processing of Pro‐Opiomelanocortin

Bicknell

2008

J Neuroendocrinology

118

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In 1967, a new era in endocrinology was born. A set of pulse chase experiments performed by Steiner and Oyer (1) elegantly showed, for the first time, that insulin was derived from a larger precursor molecule, proinsulin. The radical revelation, that bioactive peptides are derived from larger precursors, forever changed endocrinology and, from then on, the concept of hormone precursors (or prohormones) has become a central dogma. Subsequently, the use of both traditional protein sequence studies and recombinant DNA technology have provided definitive structures for the precursors of all the known bioactive peptides as well as identifying several previously unknown precursors, the function of which are still not fully understood. In general, all these molecules contain within their sequence one or more copies of the active peptide while some contain several different bioactive peptides. In addition, they undergo a series of highly regulated post-translational events that includes specific proteolytic cleavage and modifications such as amidation, acetylation and phophorylation. These post-translational processing events are especially interesting because there are a number of examples where the extent of processing can yield very different bioactive peptides from the same precursor. Probably the best example of this phenomenon, and arguably the most studied prohormone, is the ACTH precursor pro-opiomelanocortin (POMC). This short review aims to highlight why it has been of such interest to (neuro)endocrinologists and suggests that it still has a few more secrets to yield. Discovery of POMCThe discovery of POMC ( Fig. 1) was preceded by a number of what, at the time, appeared to be unrelated observations. Both ACTH and a-melanocyte-stimulating hormone (a-MSH) had been purified and sequenced from the pituitaries of various species. However, the fact that a-MSH has the same amino acid sequence as the first 13 residues of ACTH was not seen to be of much significance until the isolation of corticotrophin-like intermediate peptide (CLIP) (2), the peptide that comprises the C-terminal of ACTH. This, together with the identification of larger molecular weight forms of immunoreactive ACTH (3, 4), began to suggest that ACTH and a-MSH were indeed derived from the same molecule.A further observation suggesting the existence of a common precursor to a number of pituitary hormones was that the sequence of the newly-discovered pituitary peptide, b-endorphin (5, 6), which had strong opiate-like activity, shared the same sequence as the C-terminal of b-lipotrophin (b-LPH), another pituitary hormone released under the same conditions as ACTH. It was subsequently shown that b-LPH was expressed in the same pituitary cells as a-MSH and CLIP (7).In 1976, the first published report came that suggested ACTH and b-LPH were derived from the same molecule (8) It is just over 30 years since the definitive identification of the adrenocorticotrophin (ACTH) precursor, pro-opiomelanocotin (POMC). Although first characterised in the anterior and...

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Immunocytochemical evidence of intragranular acetylation of ?-MSH in the melanotrophic cells of the rabbit

Stoeckel¹,

Schimchowitsch²,

Garaud

et al. 1983

Cell Tissue Res.

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Melanotrophic cells of the pars intermedia of the rabbit were studied at the electron-microscopic level by means of the immuno-gold technique with the use of antisera against gamma 3-MSH and alpha-MSH. Both antibodies labelled all secretory vesicles stored in the peripheral cytoplasm, but secretory vesicles and intrasaccular condensations in the Golgi area reacting for gamma 3-MSH were not labelled with the antibody against alpha-MSH. Since this antibody appears to recognise only the acetylated form of alpha-MSH, the present observations suggest that acetylation occurs at a stage subsequent to the Golgi packaging, during maturation of the secretory vesicles. Thus, the morphological evidence supports biochemical data in favour of intragranular processing of opiomelanocortin in melanotrophic cells.

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Comparison of Rat Anterior and Intermediate Pituitary in Tissue Culture: Corticotropin (ACTH) and β‐Endorphin

Cited by 10 publications

References 42 publications

POMC: The Physiological Power of Hormone Processing

POMC: The Physiological Power of Hormone Processing

The Tissue‐Specific Processing of Pro‐Opiomelanocortin

Immunocytochemical evidence of intragranular acetylation of ?-MSH in the melanotrophic cells of the rabbit

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