Tài liệu Báo cáo khoa học: An ecdysteroid-inducible insulin-like growth factor-like peptide

An ecdysteroid-inducible insulin-like growth factor-like

peptide regulates adult development of the silkmoth

Bombyx mori

Naoki Okamoto1

, Naoki Yamanaka2,*, Honoo Satake3

, Hironao Saegusa1,, Hiroshi Kataoka2 and

Akira Mizoguchi1

1 Division of Biological Science, Graduate School of Science, Nagoya University, Japan

2 Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba,

Japan

3 Suntory Institute for Bioorganic Research, Osaka, Japan

Keywords

Bombyx mori; ecdysteroid; fat body;

insulin-like growth factors (IGFs);

insulin-like peptides

Correspondence

A. Mizoguchi, Division of Biological Science,

Graduate School of Science, Nagoya

University, Furo-cho, Chikusa-ku, Nagoya

464-8602, Japan

Fax: +81 52 789 2511

Tel: +81 52 789 5039

E-mail: [email protected]

Present address

*Department of Genetics, Cell Biology

& Development, University of Minnesota,

Mineapolis, MN, USA

Department of Pharmacology and Neurobi￾ology, Graduate School of Medicine, Tokyo

Medical and Dental University, Japan

Database

The sequence reported in this article has

been deposited in the GenBank database

(http://www.ncbi.nlm.nih.gov/Genbank)

under accession numbers AB360450–

AB360454

(Received 10 October 2008, revised 11

December 2008, accepted 16 December

2008)

doi:10.1111/j.1742-4658.2008.06859.x

Insulin-like growth factors (IGFs) play essential roles in fetal and postnatal

growth and development of mammals. They are secreted by a wide variety

of tissues, with the liver being the major source of circulating IGFs, and

regulate cell growth, differentiation and survival. IGFs share some biologi￾cal activities with insulin but are secreted in distinct physiological and

developmental contexts, having specific functions. Although recent analyses

of invertebrate genomes have revealed the presence of multiple insulin fam￾ily peptide genes in each genome, little is known about functional diversifi￾cation of the gene products. Here we show that a novel insulin family

peptide of the silkmoth Bombyx mori, which was purified and sequenced

from the hemolymph, is more like IGFs than like insulin, in contrast to

bombyxins, which are previously identified insulin-like peptides in B. mori.

Expression analysis reveals that this IGF-like peptide is predominantly

produced by the fat body, a functional equivalent of the vertebrate liver

and adipocytes, and is massively released during pupa–adult development.

Studies using in vitro tissue culture systems show that secretion of the

peptide is stimulated by ecdysteroid and that the secreted peptide promotes

the growth of adult-specific tissues. These observations suggest that this

peptide is a Bombyx counterpart of vertebrate IGFs and that functionally

IGF-like peptides may be more ubiquitous in the animal kingdom than

previously thought. Our results also suggest that the known effects of

ecdysteroid on insect adult development may be in part mediated by

IGF-like peptides.

Abbreviations

20E, 20-hydroxyecdysone; 8K-BLP, 8 kDa bombyxin-like peptide; BIGFLP, Bombyx mori insulin-like growth factor-like peptide; BrdU,

bromodeoxyuridine; DAPI, 4¢,6-diamidino-2-phenylindole; DILP, Drosophila insulin-like peptide; IGF, insulin-like growth factor; ILP, insulin-like

peptide; qRT-PCR, real-time quantitative RT-PCR.

FEBS Journal 276 (2009) 1221–1232 ª 2009 The Authors Journal compilation ª 2009 FEBS 1221