Matsuura Yuta, Yabu Takeshi, Shiba Hajime, Moritomo Tadaaki, Nakanishi Teruyuki
Department of Veterinary Medicine, Nihon University, Fujisawa, Kanagawa 252-0880, Japan.
Department of Applied Biological Science, Nihon University, Fujisawa, Kanagawa 252-0880, Japan.
Dev Comp Immunol. 2014 Oct;46(2):499-507. doi: 10.1016/j.dci.2014.06.006. Epub 2014 Jun 23.
Granzymes (Gzms) are serine proteases released from cytoplasmic granules within cytotoxic T lymphocytes and natural killer (NK) cells. Gzms induce apoptosis within virus-infected and transformed cells. In fish as well as mammals, Gzms appear to play a major role in inducing target cell death. However, information on the function of fish Gzms is limited, although Gzm-like genes have been reported in several species. We identified and characterized a fish Gzm (termed gcGzm) in ginbuna crucian carp, Carassius auratus langsdorfii. The primary structure of gcGzm resembled mammalian GzmB, and gcGzm clustered with mammalian GzmB by phylogenetic tree analysis. gcGzm was secreted from HEK293T cells transfected with gcgzm cDNA and was predominantly expressed in CD8(+) T cells, as in mammals. Expression of gcgzm mRNA was greatly enhanced by allo-sensitization and infection with the intracellular pathogen Edwardsiella tarda, indicating that gcGzm is involved in cell-mediated immunity. However, its enzymatic activity was different from mammalian Gzms because gcGzm did not cleave the known substrates for mammalian Gzms. Thus we conclude that the newly discovered gcGzm is a novel secretory serine protease involved in cell-mediated immunity in fish, with similar structure to human GzmB but different substrate specificity.
颗粒酶（Gzms）是细胞毒性T淋巴细胞和自然杀伤（NK）细胞胞质颗粒中释放的丝氨酸蛋白酶。颗粒酶可诱导病毒感染细胞和转化细胞发生凋亡。在鱼类和哺乳动物中，颗粒酶似乎在诱导靶细胞死亡中起主要作用。然而，尽管在几个物种中都报道了类颗粒酶基因，但关于鱼类颗粒酶功能的信息仍然有限。我们在日本金鱼（Carassius auratus langsdorfii）中鉴定并表征了一种鱼类颗粒酶（称为gcGzm）。gcGzm的一级结构类似于哺乳动物的颗粒酶B，并且通过系统发育树分析，gcGzm与哺乳动物的颗粒酶B聚类在一起。与哺乳动物一样，gcGzm由转染了gcgzm cDNA的HEK293T细胞分泌，并且主要在CD8(+) T细胞中表达。通过同种异体致敏和感染细胞内病原体迟缓爱德华氏菌，gcgzm mRNA的表达大大增强，这表明gcGzm参与细胞介导的免疫。然而，其酶活性与哺乳动物的颗粒酶不同，因为gcGzm不能切割哺乳动物颗粒酶的已知底物。因此，我们得出结论，新发现的gcGzm是一种新型分泌性丝氨酸蛋白酶，参与鱼类细胞介导的免疫，其结构与人类颗粒酶B相似，但底物特异性不同。
