Tài liệu Báo cáo khoa học: Characterization of chitinase-like proteins (Cg-Clp1 and Cg-Clp2)

Characterization of chitinase-like proteins (Cg-Clp1 and

Cg-Clp2) involved in immune defence of the mollusc

Crassostrea gigas

Fabien Badariotti, Christophe Lelong, Marie-Pierre Dubos and Pascal Favrel

Universite´ de Caen Basse-Normandie, IBFA, UMR M100 IFREMER, Physiologie et Ecophysiologie des Mollusques Marins, Laboratoire de

Biologie et Biotechnologies Marines, Caen, France

Glycoside hydrolase family 18 (GH18) is a phylogenet￾ically conserved group of proteins present in eukaryo￾tes, prokaryotes and viruses. The GH18 family is

characterized by a Glyco_18 domain adopting an

(a ⁄ b)8 triose phosphate isomerase-barrel structure that

consists of a specific arrangement of eight parallel

b-strands, forming the barrel core, surrounded by eight

a-helices [1]. This family classification, based only on

similarities in amino acid sequences, groups together

chitinases and proteins devoid of catalytic activity due

to the substitution of a critical amino acid in the cata￾lytic centre. This latter singular class of proteins, called

chitinase-like proteins (CLPs), has been identified only

recently in plants [2], mammals [3], insects [4] and mol￾luscs [5]. CLPs have been implicated in many biologi￾cal processes, such as control of nodulation [2] and

growth ⁄ differentiation balance during development in

plants [6]. Insect CLPs such as imaginal disc growth

factors represent the first proliferating polypeptides

reported from invertebrates [7]. These mitogenic

growth factors cooperate with insulin to stimulate pro￾liferation, polarization and mobility of imaginal disc

cells in vitro. Imaginal disc growth factors may also

constitute morphogenetic factors controlling embryonic

and larval development, and could stimulate the cell

growth required for wound healing [8,9]. In mammals,

CLPs such as YM1 ⁄ 2 and YKL-40 (40 kDa mamma￾lian protein with the N-terminus YKL) [also known as

human cartilage glycoprotein-39 (HC-gp39) in humans]

are considered to be cytokines [10,11] involved in tis￾sue remodelling during pathological conditions [12,13].

Recently, the first lophotrochozoan CLP was identified

Keywords

chitinase-like protein; Crassostrea gigas;

immunity; lectin; mollusk

Correspondence

P. Favrel, Universite´ de Caen Basse￾Normandie, IBFA, UMR M100 IFREMER,

Physiologie et Ecophysiologie des

Mollusques Marins, 14032 Caen cedex,

France

Fax: +33 231565346

Tel: +33 231565361

E-mail: [email protected]

(Received 22 February 2007, revised

10 May 2007, accepted 23 May 2007)

doi:10.1111/j.1742-4658.2007.05898.x

Chitinase-like proteins have been identified in insects and mammals as non￾enzymatic members of the glycoside hydrolase family 18. Recently, the first

molluscan chitinase-like protein, named Crassostrea gigas (Cg)-Clp1, was

shown to control the proliferation and synthesis of extracellular matrix

components of mammalian chondrocytes. However, the precise physiologi￾cal roles of Cg-Clp1 in oysters remain unknown. Here, we report the clo￾ning and the characterization of a new chitinase-like protein (Cg-Clp2)

from the oyster Crassostrea gigas. Gene expression profiles monitored by

quantitative RT-PCR in adult tissues and through development support its

involvement in tissue growth and remodelling. Both Cg-Clp1- and Cg￾Clp2-encoding genes were transcriptionally stimulated in haemocytes in

response to bacterial lipopolysaccharide challenge, strongly suggesting that

these two close paralogous genes play a role in oyster immunity.

Abbreviations

Cg-Clp1 ⁄ 2, Crassostrea gigas chitinase-like protein 1 ⁄ 2; CLP, chitinase-like protein; GAPDH, glyceraldehyde-3-phosphate dehydrogenase;

GH, glycoside hydrolase; HC-gp39, human cartilage glycoprotein-39 (also called YKL-40); LPS, lipopolysaccharide; YKL-40, 40 kDa

mammalian protein with the N-terminus YKL.

3646 FEBS Journal 274 (2007) 3646–3654 ª 2007 The Authors Journal compilation ª 2007 FEBS