Release of α-Subunit of Glycoprotein Hormones from the Bullfrog Pituitary: Possible Effect of α-Subunit on Prolactin Cell Function

Oguchi, Atsuko; Tanaka, Shigeyasu; Yamamoto, Kazutoshi; Kikuyama, Sakaé

doi:10.1006/gcen.1996.0055

Cited by 27 publications

(12 citation statements)

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“…Effect of Ghrelin on Adenohypophyseal Hormone Secretion in Bullfrog Pituitary Cells-We examined the effect of ghrelin on the secretion of adenohypophyseal hormones, such as GH, PRL, follicle-stimulating hormone (FSH), and luteinizing hormone (LH), in dispersed bullfrog anterior pituitary cells (21). Bullfrogs purchased from a commercial supplier (Ohuchi, Saitama, Japan) in July and October were sacrificed by decapitation.…”

Section: Methodsmentioning

confidence: 99%

Bullfrog Ghrelin Is Modified by n-Octanoic Acid at Its Third Threonine Residue

Kaiya¹,

Kojima²,

Hosoda³

et al. 2001

Journal of Biological Chemistry

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155

101

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We have identified the amphibian ghrelin from the stomach of the bullfrog. We also examined growth hormone (GH)-releasing activity of this novel peptide in both the rat and bullfrog. The three forms of ghrelin identified, each comprised of 27 or 28 amino acids, possessed 29% sequence identity to the mammalian ghrelins. A unique threonine at amino acid position 3 (Thr 3 ) in bullfrog ghrelin differs from the serine present in the mammalian ghrelins; this Thr 3 is acylated by either n-octanoic or n-decanoic acid. The frog ghrelin-28 has a complete structure of GLT (O-n-octanoyl)FLSPAD-MQKIAERQSQNKLRHGNM; the structure of frog ghrelin-27 was determined to be GLT(O-n-octanoyl)FLSPAD-MQKIAERQSQNKLRHGN; frog ghelin-27-C10 possessed a structure of GLT(O-n-decanoyl)FLSPADMQKIAER-QSQNKLRHGN. Northern blot analysis demonstrated that ghrelin mRNA is predominantly expressed in the stomach. Low levels of gene expression were observed in the heart, lung, small intestine, gall bladder, pancreas, and testes, as revealed by reverse transcription polymerase chain reaction analysis. Bullfrog ghrelin stimulated the secretion of both GH and prolactin in dispersed bullfrog pituitary cells with potency 2-3 orders of magnitude greater than that of rat ghrelin. Bullfrog ghrelin, however, was only minimally effective in elevating plasma GH levels following intravenous injection into rats. These results indicate that although the regulatory mechanism of ghrelin to induce GH secretion is evolutionary conserved, the structural changes in the different ghrelins result in species-specific receptor binding. Growth hormone (GH)1 secretion from the pituitary gland is regulated by hypothalamic hormones; growth hormone-releasing hormone (GHRH) stimulates GH secretion, whereas somatostatin is inhibitory (1). Derivatives of Met-enkephalin stimulate GH release (2), the first demonstration that small synthetic peptides and nonpeptide molecules, dubbed growth hormone secretagogues (GHSs), can mediate GH release through a receptor distinct from that of GHRH (3-5). The G-protein-coupled GHS receptor (GHS-R) was subsequently identified in swine, rat, and human (6, 7), suggesting that one or more unknown ligands for this receptor are endogenously present.We recently discovered an endogenous ligand for GHS-R from the rat stomach, using an intracellular calcium influx assay in stable cell lines expressing rat GHS-R (8). This novel molecule, a 28-amino acid peptide named ghrelin (from "ghre," the Proto-Indo-European root of "grow"), possesses a unique serine residue at the third N-terminal position (Ser 3 ) that is n-octanoylated (8, 9). Acylation of Ser 3 is essential for ghrelin bioactivity. cDNA analysis revealed that the rat ghrelin sequence follows the 23-residue signal sequence within the 117-residue prepro-ghrelin. Ghrelin stimulates GH secretion both in vivo and in vitro. Accumulating evidence in mammals suggests that, in addition to regulating GH release, ghrelin also influences feeding behavior (10, 11), gastrointestinal function (12, 13), and ener...

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Section: Methodsmentioning

confidence: 99%

Bullfrog Ghrelin Is Modified by n-Octanoic Acid at Its Third Threonine Residue

Kaiya¹,

Kojima²,

Hosoda³

et al. 2001

Journal of Biological Chemistry

Self Cite

155

101

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“…For example, the free ␣-subunit induces differentiation of PRL cells in fetal pituitary cultures (Begeot et al 1983), stimulates synergistically with progesterone the differentiation of cultured human endometrial stromal cells to decidualized cells (Moy et al 1996), stimulates secretion of prolactin from human decidual cells in pregnancy (Blithe et al 1991), and stimulates PRL release from the bullfrog pituitary (Oguchi et al 1996;Tanaka et al 1992). Moreover, the crystalline structure of the ␣-subunit reveals that its tertiary structure is a cystine knot formed by three disulfide bridges.…”

Section: Discussionmentioning

confidence: 99%

“…The ␣-subunit is considered to be identical in amino acid sequence among all these glycoprotein hormones within one species (Hayashi et al 1992;Pierce and Parsons 1981). Recently, several reports have documented that a certain amount of the free ␣-subunit of glycoprotein hormones is secreted from the normal pituitary, suggesting that this subunit may possibly play physiological roles (Oguchi et al 1996;Begeot et al 1983Begeot et al ,1984. In addition, human neoplastic pituitaries (Beck-Peccoz et al 1985Osamura and Watanabe 1987;Landolt and Heitz 1986;Capella et al 1983;Klibanski et al 1983;Kourides et al 1976) and human carcinoid tumors (Fukayama et al 1986(Fukayama et al ,1987Heitz et al 1983;Wahlstrom and Seppala 1981) have also been shown to produce the ␣-subunit, but not the ␤-subunit, of LH, FSH, and TSH.…”

mentioning

confidence: 99%

Production and Characterization of Specific Anti-peptide Antiserum Against Free α-subunit of Rat Pituitary Glycoprotein Hormones

Tanaka

Kurabuchi²,

Mochida³

et al. 1997

J Histochem Cytochem.

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SUMMARY To obtain an antibody specific for the ␣-subunit of rat pituitary glycoprotein hormones, we synthesized a peptide corresponding to the sequence 37-53 (ST-7: Phe-SerArg-Ala-Tyr-Pro-Thr-Pro-Ala-Arg-Ser-Lys-Lys-Thr-Met-Leu-Val) of the rat ␣-subunit. The polyclonal antiserum against this peptide was generated in rabbits. This region is hydrophilic and highly conserved among several mammalian species. Noncompetitive binding tests showed that the ST-7 antiserum had specific affinity for the rat free ␣-subunit, but not for rat intact LH, FSH, and TSH. The ST-7 antiserum immunostained two types of cells in the rat anterior pituitary, i.e., gonadotrophs and thyrotrophs. This was also the case in mouse, cattle, sheep, and pig, which have an identical sequence of ST-7 in their ␣-subunit. The pituitary cells of horse (Arg substituted for Lys as residue 48 of the rat ␣-subunit), human, and eel (Leu for Ala at residue 45), chicken (Met for Ala at residue 45), and bullfrog (Tyr for Phe at residue 37 and Met for Ala at residue 45) were not stained with the ST-7 antiserum. This study indicated that the ST-7 antiserum is sequence-specific for the ␣-subunit and is therefore useful for immunohistochemical studies on the secretory pathway of the free ␣-subunit. (J Histochem Cytochem 45:985-990, 1997)

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“…Preparation of anterior pituitary cells of the bullfrog was performed according to the procedures described elsewhere (Oguchi et al, 1996). The enzymatically dispersed anterior pituitary cells were suspended in 70% Medium 199 (M199; Nissui Pharmaceutical, Tokyo, Japan) containing 0.1% BSA (Fraction V; Sigma, St. Louis, MO).…”

Section: Cell Incubation and Hormone Assaymentioning

confidence: 99%

“…In amphibians, we have also demonstrated that pituitary hormones or substances present in the pituitary cells act in a paracrine and/or autocrine fashion to regulate the release of pituitary hormones. In the bullfrog (Rana catesbeiana), the α-subunit of glycoprotein hormones stimulates prolactin (PRL) release (Oguchi et al, 1996), PRL enhances the release of luteinizing hormone (LH) , and endothelin-3 existing in gonadotrophs (Suzuki et al, 1997a) stimulates the release of growth hormone (GH) and PRL (Suzuki et al, 1997b). Proopiomelanocortin (POMC)-derived peptides, namely, the N-terminal peptide of POMC (NPP), and adrenocorticotropic hormone (ACTH) enhance the release of LH , GH and PRL (Aida et al, 1999).…”

Section: Introductionmentioning

confidence: 99%