Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources and College of Fisheries and Life Science, Shanghai Ocean University, 999 Hucheng Ring Road, Shanghai 201306, China.
Fish Shellfish Immunol. 2013 Aug;35(2):581-8. doi: 10.1016/j.fsi.2013.06.001. Epub 2013 Jun 10.
Cathepsin L (CTSL) is a lysosomal cysteine protease involved in immune responses in vertebrates. However, few studies exist regarding the role of cathepsin L in bivalves. In this study, we isolated and characterized four cathepsin L genes from the razor clam Sinonovacula constricta, referred to as CTSL1, CTSL2, CTSL3 and CTSL4. These four genes contained typical papain-like cysteine protease structure and enzyme activity sites with ERWNIN-like and GNFD-like motifs in the proregion domain and an oxyanion hole (Gln) and a catalytic triad (Cys, His and Asn) in the mature domain. Expression analysis of the four transcripts revealed a tissue-specific pattern with high expression of CTSL1 and CTSL3 in liver and gonad tissues and high expression of CTSL2 and CTSL4 in liver and gill tissues. During the developmental stages, the four transcripts showed the highest expression in the juvenile stage; however, CTSL3 had a much higher expression level than the other three transcripts during embryogenesis. The four transcripts showed significant changes in expression as early as 4 h or 8 h after infection with Vibrio anguillarum. The fact that bacterial infection can induce expression of the four CTSL transcripts suggests that these transcripts are important components of the innate immunity system of the clam.
组织蛋白酶 L（CTSL）是脊椎动物免疫反应中涉及的溶酶体半胱氨酸蛋白酶。然而，关于贝类组织蛋白酶 L 的作用的研究很少。在这项研究中，我们从中国蛤蜊（Sinonovacula constricta）中分离并鉴定了四个组织蛋白酶 L 基因，分别命名为 CTSL1、CTSL2、CTSL3 和 CTSL4。这四个基因具有典型的木瓜蛋白酶样半胱氨酸蛋白酶结构和酶活性位点，在前导域具有 ERWNIN 样和 GNFD 样基序，在成熟域具有氧阴离子空洞（Gln）和催化三联体（Cys、His 和 Asn）。四个转录本的表达分析显示出组织特异性模式，CTSL1 和 CTSL3 在肝和性腺组织中高表达，CTSL2 和 CTSL4 在肝和鳃组织中高表达。在发育阶段，四个转录本在幼体阶段表达最高；然而，在胚胎发生过程中，CTSL3 的表达水平比其他三个转录本高得多。四种转录本在感染鳗弧菌后 4 小时或 8 小时就表现出明显的表达变化。细菌感染能诱导四个 CTSL 转录本的表达这一事实表明，这些转录本是蛤蜊先天免疫系统的重要组成部分。
