Elsevier

Peptides

Volume 25, Issue 11, November 2004, Pages 2027-2038
Peptides

Review
Biological importance of the peptides of the calcitonin family as revealed by disruption and transfer of corresponding genes☆

https://doi.org/10.1016/j.peptides.2004.08.007Get rights and content

Abstract

The hormone calcitonin (CT) of thyroid C-cell origin, the neuropeptides α- and β-calcitonin gene-related peptide (CGRP), the widely expressed hormone and tissue factor adrenomedullin (AM), and amylin (AMY) that is co-produced with insulin in pancreatic β-cells, are structurally related peptides. They have in common six or seven amino acid ring structures, linked by disulfide bridges between cysteine residues, and amidated carboxyl termini that are both required for biological activity. The actions of the peptides in vivo have traditionally been studied after intravenous and intracerebroventricular administration. As a result, CT lowers serum calcium and reduces pain perception. α- and βCGRP and AM are highly potent vasodilatory peptides. AMY inhibits food intake through its action in the area postrema of the brain. Physiological actions of the peptides summarized in the present review have been defined through gene knockout and overexpression strategies.

Introduction

Calcitonin (CT) is almost exclusively produced in thyroid C-cells and the secretion is stimulated by increased levels of the serum calcium (for review see [65]). The principal targets of the hypocalcemic action of CT are the bone and the kidneys, where CT inhibits osteoclastic bone resorption and stimulates the urinary excretion of calcium. A distinct effect of CT is a reduction of pain perception.

α-Calcitonin gene-related peptide (αCGRP) together with CT are the products of the same gene [4]. αCGRP is predominantly produced in the nervous system through tissue-specific alternative splicing of the initial gene transcript. The CT/αCGRP gene has six exons. mRNA encoding the precursor of CT consists of the exons 1, 2, 3, and 4 and is predominantly expressed in thyroid C-cells. The mRNA encoding the αCGRP precursor in the nervous system contains the exons 1, 2, 3, 5, and 6. αCGRP is a potent vasodilator and it lowers in pharmacologic amounts the arterial pressure (for review see [108]). αCGRP increases the heart rate directly, but its inotropic actions on the heart are brought about through activation of the sympathetic nervous system. βCGRP is encoded by a different, but closely related gene. It has an exon 4 with a translational stop codon and as a result is a CT pseudogene [3]. The biological actions of α- and βCGRP are overlapping, but α- and βCGRP exert distinct hemodynamic and gastric effects in normal man [9].

Adrenomedullin (AM) initially identified in the adrenal medulla is widely distributed and produced predominantly in vascular smooth muscle and endothelial cells [52]. Much like CGRP, AM is a potent vasodilator (for review see [31]). Other important actions include bronchodilation, natriuresis as well as regulation of cell growth, differentiation, and apoptosis.

Amylin (AMY) is synthesized and secreted together with insulin from pancreatic β-cells in response to elevated serum glucose levels [107]. AMY inhibits insulin secretion, gluconeogenesis in the skeletal musculature as well as food intake and gastric emptying [81]. Amyloid deposits in the pancreas have been implicated in the pathogenesis of diabetes type II [33].

Recently, calcitonin receptor stimulating peptides (CRSP)-1, -2, and -3 have been identified in the brain and the thyroid gland of the pig, dog, and cow, but not in man and mouse [45], [46], [47]. CRSP1 exhibits 60% amino acid sequence similarity with CGRP. CRSP1 elicits a transient decrease in serum calcium levels in anesthetized rats, but does not lower blood pressure.

Four AM-like peptides, AM2, -3, -4, and -5, have been identified in teleost fish [76]. AM2, named intermedin, has also been found in man, rat, and mouse [82], [94]. In fish, AM2 encoding mRNA is mainly expressed in the brain [76]. In mice, the mRNA is expressed in the submaxillary gland, kidney, stomach, and mesentery and the protein is found in the pituitary and the stomach [94]. In man, the mRNA is expressed in the gastrointestinal tract mainly in the stomach and jejunum [82]. In the mouse, AM2 was more potent than AM in lowering arterial pressure, and renal water and sodium excretion [94]. Physiological roles of CRSP and AM2 remain to be better understood.

CT interacts with a seven transmembrane domain G protein-coupled receptor (CTR) of the family B, cloned in 1991 [55]. CGRP and AM are recognized by a closely related receptor, the calcitonin receptor-like receptor (CLR) in association with receptor-activity-modifying proteins (RAMP) [63], [79]. The three identified RAMP1, -2, and -3 are single transmembrane domain proteins with an extracellular N-terminal region of between 90 and 100 amino acids and a short intracellular C-terminus of about 10 amino acids [66], [88]. CRL/RAMP1 heterodimers are receptors for α- and βCGRP predominantly linked to cAMP production and inhibited by αCGRP(8–37) lacking the N-terminal ring structure of intact αCGRP [39]. The CLR associated with RAMP2 is an AM receptor antagonized by human AM(22–52). Association of RAMP3 with the CLR reveals a mixed type AM/CGRP receptor. Interaction of CT with the CTR does not require the detectable expression of a RAMP. AMY binds to the CTR/RAMP1 and -3 complexes [18], [67]. The CTR/RAMP1, unlike CTR/RAMP3 heterodimers, recognize also CGRP with an affinity similar to that of the CLR/RAMP1 complex [53]. CTR/RAMP1 CGRP receptors are antagonized by salmon CT(8–32) but not by CGRP(8–37). CRSP1 interacts with the CTR and stimulates cAMP production with the potency of CT [45]. CRSP2 and -3 do not stimulate cAMP in COS-7 cells transfected with the CTR. CRSP1, -2, and -3 do not activate CLR/RAMP1, -2, or -3 heterodimers. AM2 stimulates cAMP production in human neuroblastoma SK-N-MC and rat L6 skeletal myoblast cells through endogenous CGRP receptors [82]. The EC50 of AM2 is 10-fold higher than that of CGRP, and the cAMP response is antagonized by CGRP(8–37).

This review focuses on the ablation and overexpression of the genes encoding the peptides of the calcitonin family (Table 1). CTR knockout mice have recently been generated [21].

Section snippets

Strategies of targeted gene ablation

The CT gene consists of six exons with the exons 4 and 5 encoding CT and αCGRP, respectively [4]. Alternative tissue-specific splicing reveals two distinct mRNA products encoding preproCT in thyroid C-cells or preproαCGRP in neuronal tissues of the rat. Homozygous αCGRP knockout mice with normal CT expression were obtained through targeted disruption of exon 5 of the CT/αCGRP gene [7], [77], [83], [84], [85], [87] or by the introduction of a stop codon upstream of the αCGRP encoding sequence in

The AM/PAMP gene and knockout strategies

The mouse AM gene is located on chromosome 7 [78]. It has four exons encoding preproAM. Exons 2 and 3 encode the proadrenomedullin N-20 terminal peptide (PAMP) and exon 4 AM. In AM selective knockout mice a stop codon was introduced in front of the AM coding region [49], [61], [90], [109]. In AM/PAMP knockouts exons 1–3 and part of exon 4 were replaced with a neomycin resistance gene [40], [72], [73], [74], [75], [92] or exons 1–4 were replaced by the enhanced green fluorescent protein and a

Amylin knockout

The mouse AMY gene is located on chromosome 6 and consists of three exons encoding preproamylin [25]. Exon 3 encodes AMY. AMY knockout mice have been generated by targeting exon 3 [14], [21], [28], [29], [64], [68]. Since mouse AMY is not amyloidogenic transgenic animals were generally generated with human AMY.

AMY−/−-deficient mice appeared healthy and were born with Mendelian frequencies [28]. They have normal basal plasma insulin and glucose levels, gonadal fat pad weight, food intake, islet

References (114)

  • T. Katafuchi et al.

    Calcitonin receptor-stimulating peptide, a new member of the calcitonin gene-related peptide family

    J. Biol. Chem.

    (2003)
  • K. Kitamura et al.

    Adrenomedullin: a novel hypotensive peptide isolated from human pheochromocytoma

    Biochem. Biophys. Res. Commun.

    (1993)
  • J.T. Lu et al.

    Mice lacking α-calcitonin gene-related peptide exhibit normal cardiovascular regulation and neuromuscular development

    Mol. Cell. Neurosci.

    (1999)
  • J.M. Lundberg et al.

    Co-existence of substance P and calcitonin gene-related peptide- like immunoreactivities in sensory nerves in relation to cardiovascular and bronchoconstrictor effects of capsaicin

    Eur. J. Pharmacol.

    (1985)
  • A. Mollet et al.

    Endogenous amylin contributes to the anorectic effects of cholecystokinin and bombesin

    Peptides

    (2003)
  • R. Muff et al.

    Adrenomedullin and related peptides: receptors and accessory proteins

    Peptides

    (2001)
  • M. Ogoshi et al.

    Identification of a novel adrenomedullin gene family in teleost fish

    Biochem. Biophys. Res. Commun.

    (2003)
  • T. Okazaki et al.

    Genomic organization, expression, and chromosomal mapping of the mouse adrenomedullin gene

    Genomics

    (1996)
  • J. Roh et al.

    Intermedin is a calcitonin/calcitonin gene-related peptide family peptide acting through the calcitonin receptor-like receptor/receptor activity-modifying protein receptor complexes

    J. Biol. Chem.

    (2004)
  • A-M. Salmon et al.

    Reduction of withdrawal signs after chronic nicotine exposure of alpha-calcitonin gene-related peptide knock-out mice

    Neurosci. Lett.

    (2004)
  • P.M. Sexton et al.

    Receptor activity modifying proteins

    Cell. Signal.

    (2001)
  • Y. Takei et al.

    Identification of novel adrenomedullin in mammals: a potent cardiovascular and renal regulator

    FEBS Lett.

    (2004)
  • S.G. Amara et al.

    Expression in brain of a messenger RNA encoding a novel neuropeptide homologous to calcitonin gene-related peptide

    Science

    (1985)
  • S.G. Amara et al.

    Alternative RNA processing in calcitonin gene expression generates mRNAs encoding different polypeptide products

    Nature

    (1982)
  • S. Andrikopoulos et al.

    Two novel immortal pancreatic β-cell lines expressing and secreting human islet amyloid polypeptide do not spontaneously develop islet amyloid

    Diabetes

    (1999)
  • S. Andrikopoulos et al.

    β-Cell glukokinase deficency and hyperglycemia are associated with reduced islet amyloid deposition in a mouse model of type 2 diabetes

    Diabetes

    (2000)
  • T. Aoki-Nagase et al.

    Attenuation of antigen-induced airway hyperresponsiveness in CGRP-deficient mice

    Am. J. Physiol. Lung Cell. Mol. Physiol.

    (2002)
  • R. Ballica et al.

    Targeted expression of calcitonin gene-related peptide to osteoblasts increases bone density in mice

    J. Bone Miner. Res.

    (1999)
  • T.J. Bivalacqua et al.

    Gene transfer of prepro-calcitonin gene-related peptide restores erectile function in the aged rat

    Biol. Reprod.

    (2001)
  • A.E. Butler et al.

    Diabetes due to a progressive defect in β-cell mass in rats transgenic for human islet amyloid polypeptide (HIP rat)

    Diabetes

    (2004)
  • A.E. Butler et al.

    Increased β-cell apoptosis prevents adaptive increase in β-cell mass in mouse model of type 2 diabetes

    Diabetes

    (2003)
  • P-A. Carlsson et al.

    Unaltered pancreatic islet blood perfusion in islet amyloid polypeptide-deficient mice

    Eur. J. Endocrinol.

    (2002)
  • K.M. Caron et al.

    Extreme hydrops fetalis and cardiovascular abnormalities in mice lacking a functional adrenomedullin gene

    Proc. Natl. Acad. Sci. USA

    (2001)
  • H.C. Champion et al.

    In vivo gene transfer of prepro-calcitonin gene-related peptide to the lung attenuates chronic hypoxia-induced pulmonary hypertension in the mouse

    Circulation

    (2000)
  • J. Chao et al.

    Adrenomedullin gene delivery reduces blood pressure in spontaneously hypertensive rats

    Hypertens Res.

    (1997)
  • G. Christopoulos et al.

    Multiple amylin receptors arise from receptor activity-modifying protein interaction with the calcitonin receptor gene product

    Mol. Pharmacol.

    (1999)
  • M. Couce et al.

    Treatment with growth hormone and dexamethasone in mice transgenic for human islet amyloid polypeptide causes islet amyloidosis and β-cell dysfunction

    Diabetes

    (1996)
  • D.A. D’Alessio et al.

    Pancreatic expression and secretion of human islet amyloid polypeptide in a transgenic mouse

    Diabetes

    (1994)
  • R. Dacquin et al.

    Amylin inhibits bone resorption while the calcitonin receptor controls bone formation in vivo

    J. Cell. Biol.

    (2004)
  • E. Devine et al.

    Weight gain in male and female mice with amylin knockout

    Diabetes

    (1998)
  • E. Dobrzynski et al.

    Adrenomedullin impoves cardiac function and prevents renal damage in streptozotocin-induced diabetic rats

    Am. J. Physiol. Endocrinol. Metab.

    (2002)
  • E. Dobrzynski et al.

    Adrenomedullin gene delivery attenuates hypertension, cardiac remodeling, and renal injury in deoxycorticosterone acetate-salt hypertensive rats

    Hypertension

    (2000)
  • K. Ekawa et al.

    Cloning of mouse islet amyloid polypeptide gene and characterization of its promoter

    J. Mol. Endocrinol.

    (1997)
  • Gangula PRR et al.

    Increased blood pressure in α-calcitonin gene-related peptide/calcitonin gene knockout mice

    Hypertension

    (2000)
  • J.G. Geisler et al.

    Estrogen can prevent or reverse obesity and diabetes in mice expresssing human islet amyloid polypeptide

    Diabetes

    (2002)
  • J.P. Hinson et al.

    Adrenomedullin, a multifunctional regulatory peptide

    Endocr. Rev.

    (2000)
  • A.O. Hoff et al.

    Increased bone mass is an unexpected phenotype associated with deletion of the calcitonin gene

    J. Clin. Invest.

    (2002)
  • Hoppener JWM et al.

    Islet amyloid and type 2 diabetes mellitus

    N Engl. J. Med.

    (2000)
  • Hoppener JWM et al.

    Extensive islet amyloid formation is induced by development of type II diabetes mellitus and contributes to its progresion: pathogenesis of diabetes in a mouse model

    Diabetologia

    (1999)
  • Hoppener JWM et al.

    Chronic overproduction of islet amyloid polypeptide/amylin in transgenic mice: lysosomal localization of human islet amyloid polypeptide and lack of marked hypergylcemia or hyperinsulinaemia

    Diabetologia

    (1993)

    • Cited by (0)

    ☆

    Joint International Symposium on Calcitonin Gene-Related Peptide, Amylin and Calcitonin – 4th Symposium on Adrenomedullin and Proadrenomedullin N-20 Peptide, Zurich, Switzerland, March 18–20, 2004.

    View full text
    Copyright © 2004 Elsevier Inc. All rights reserved.