2015年1月
Identification of activated protein C as a ghrelin endopeptidase in bovine plasma
JOURNAL OF ENDOCRINOLOGY
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- 巻
- 224
- 号
- 1
- 開始ページ
- 61
- 終了ページ
- 73
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1530/JOE-14-0529
- 出版者・発行元
- BIOSCIENTIFICA LTD
Ghrelin is a natural GH secretagogue first identified in the stomach. The ghrelin peptide is 28 amino acids long with an octanoic acid attached to Ser(3) near the N-terminus. This lipid modification is essential for the interaction between ghrelin and the ghrelin-specific receptor GH secretagogue receptor type 1a (GHSR1a), whereas the five or more residues of the N-terminus seem to be sufficient to activate GHSR1a to the same level as those of full-length ghrelin. In this study, we found that ghrelin was converted into smaller fragments during incubation with animal plasma in vitro and in a mouse model. Mass spectrometric analysis revealed that both acyl and desacyl ghrelin were hydrolyzed at the peptide bond between Arg(15) and Lys(16), generating an N-terminal peptide consisting of the first 15 residues. Next, we partially purified a ghrelin endopeptidase from bovine plasma and identified the enzyme as an anticoagulant serine protease-activated protein C. Octanoyl-truncated ghrelin(1-15) activated GHSR1a-dependent signaling similar to the full-length peptide, as assayed using the cell-based early-growth factor 1 reporter system. Moreover, administration of the protein C-activating agent, ProTac, to mice enhanced the production of octanoyl ghrelin(1-15) in circulation. These results indicate that ghrelin is processed into shorter peptides in circulation under thrombotic and inflammatory conditions, although high doses of the short-form or full-length ghrelin did not have any obvious effects on thromboplastin time or platelet aggregation in human plasma. Truncation of ghrelin might be responsible for altering structural characteristics such as stability, hydrophobicity, and affinity with circulating macromolecules.
- リンク情報
- ID情報
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- DOI : 10.1530/JOE-14-0529
- ISSN : 0022-0795
- eISSN : 1479-6805
- Web of Science ID : WOS:000347881200009