Novel neuropeptides related to frog growth hormone-releasing peptide: Isolation, sequence, and functional analysis

Kazuyoshi Ukena, Aya Koda, Kazutoshi Yamamoto, Tetsuya Kobayashi, Eiko Iwakoshi-Ukena, Hiroyuki Minakata, Sakae Kikuyama, Kazuyoshi Tsutsui

Research output: Contribution to journalArticle

87 Citations (Scopus)

Abstract

We previously identified in the bullfrog a novel hypothalamic RFamide peptide (SLKPAANLPLRF-NH2) that stimulated GH release in vitro and in vivo and therefore was designated frog GH-releasing peptide (fGRP). Molecular cloning of cDNA encoding the deduced fGRP precursor polypeptide further revealed that it encodes fGRP and its related peptides (fGRP-RP-1, -RP-2, and -RP-3). In this study immunoaffinity purification using the antibody against fGRP was therefore conducted to determine whether these three putative fGRP-RPs exist as mature endogenous ligands in the frog brain. The mass peaks of the isolated immunoreactive substances were detected at 535.78, 1034.14, and 1079.71 m/z ([M+2H]2+), and their sequences, SIPNLPQRF-NH 2, YLSGKTKVQSMANLPQRF-NH2, and AQYTNHFVHSLDTLPLRF-NH 2, were revealed by the fragmentation, showing mature forms encoded in the cDNA sequences of fGRP-RP-1, -RP-2, and -RP-3, respectively. All of these fGRP-RPs contained a C-terminal -LPXRF-NH2 (X = L or Q) sequence, such as fGRP. This study further analyzed hypophysiotropic activities of the identified endogenous fGRP-RPs. Only fGRP-RP-2 stimulated, in a dose-related way, the release of PRL from cultured frog pituitary cells; its threshold concentration ranged from less than 10-7 M. A similar stimulatory action of fGRP-RP-2 on GH release was evident. It was ascertained that fGRP-RP-2 was also effective in elevating the circulating GH and PRL levels when administered systemically. In contrast, fGRP-RPs did not have any appreciable effect on the release of gonadotropins. Thus, fGRP-RP-2 may act as a novel hypothalamic factor on the frog pituitary to stimulate the release of GH and PRL.

Original languageEnglish
Pages (from-to)3879-3884
Number of pages6
JournalEndocrinology
Volume144
Issue number9
DOIs
Publication statusPublished - 2003 Sep 1
Externally publishedYes

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

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    Ukena, K., Koda, A., Yamamoto, K., Kobayashi, T., Iwakoshi-Ukena, E., Minakata, H., Kikuyama, S., & Tsutsui, K. (2003). Novel neuropeptides related to frog growth hormone-releasing peptide: Isolation, sequence, and functional analysis. Endocrinology, 144(9), 3879-3884. https://doi.org/10.1210/en.2003-0359