Gallwitz Maike, Reimer Jenny M, Hellman Lars
Department of Cell and Molecular Biology, Program for Immunology, Uppsala University, P.O. Box 596, BMC, 75124, Uppsala, Sweden.
Immunogenetics. 2006 Aug;58(8):655-69. doi: 10.1007/s00251-006-0126-1. Epub 2006 Jun 29.
The acidic granules of natural killer (NK) cells, T cells, mast cells, and neutrophils store large amounts of serine proteases. Functionally, these proteases are involved, e.g., in the induction of apoptosis, the recruitment of inflammatory cells, and the remodeling of extra-cellular matrix. Among the granule proteases are the phylogenetically related mast cell chymases, neutrophil cathepsin G, and T-cell granzymes (Gzm B to H and Gzm N), which share the characteristic absence of a Cys(191)-Cys(220) bridge. The genes of these proteases are clustered in one locus, the mast cell chymase locus, in all previously investigated mammals. In this paper, we present a detailed analysis of the chymase locus in cattle (Bos taurus) and opossum (Monodelphis domestica). The gained information delineates the evolution of the chymase locus over more than 200 million years. Surprisingly, the cattle chymase locus contains two alpha-chymase and two cathepsin G genes where all other studied chymase loci have single genes. Moreover, the cattle locus holds at least four genes for duodenases, which are not found in other chymase loci. Interestingly, duodenases seem to have digestive rather than immune functions. In opossum, on the other hand, only two chymase locus-related genes have been identified. These two genes are not arranged in one locus, but appear to have been separated by a marsupial-specific chromosomal rearrangement. Phylogenetic analyses place one of the opossum genes firmly with mast cell alpha-chymases, which indicates that the alpha-chymase had already evolved as a separate, clearly identifiable gene before the separation of marsupials and placental mammals. In contrast, the second gene in opossum is positioned phylogenetically between granzymes, cathepsin G, and the duodenases. These genes, therefore, probably evolved as separate subfamilies after the separation of placental mammals from marsupials. In platypus, only one chymase locus-like sequence could be identified. This previously published "granzyme" does not cluster clearly with any of the chymase locus gene families, but shares the absence of the Cys(191)-Cys(220) bridge with the other chymase locus proteases. These findings indicate that all chymase locus genes are derived from a single ancestor that was present more than 200 million years ago.
自然杀伤（NK）细胞、T细胞、肥大细胞和中性粒细胞的酸性颗粒储存大量丝氨酸蛋白酶。在功能上，这些蛋白酶参与例如细胞凋亡的诱导、炎症细胞的募集以及细胞外基质的重塑。颗粒蛋白酶包括系统发育相关的肥大细胞糜蛋白酶、中性粒细胞组织蛋白酶G和T细胞颗粒酶（Gzm B至H以及Gzm N），它们共同的特征是缺乏Cys(191)-Cys(220)桥。在所有先前研究的哺乳动物中，这些蛋白酶的基因聚集在一个位点，即肥大细胞糜蛋白酶位点。在本文中，我们对牛（Bos taurus）和负鼠（Monodelphis domestica）的糜蛋白酶位点进行了详细分析。所获得的信息描绘了糜蛋白酶位点超过2亿年的进化历程。令人惊讶的是，牛糜蛋白酶位点包含两个α-糜蛋白酶和两个组织蛋白酶G基因，而所有其他研究的糜蛋白酶位点都只有单个基因。此外，牛的位点至少有四个十二指肠酶基因，而在其他糜蛋白酶位点中未发现。有趣的是，十二指肠酶似乎具有消化功能而非免疫功能。另一方面，在负鼠中，仅鉴定出两个与糜蛋白酶位点相关的基因。这两个基因并非排列在一个位点，而是似乎因有袋类动物特有的染色体重排而分开。系统发育分析将负鼠的一个基因与肥大细胞α-糜蛋白酶紧密联系在一起，这表明α-糜蛋白酶在有袋类动物和胎盘哺乳动物分离之前就已经进化为一个独立的、可明确识别的基因。相比之下，负鼠中的第二个基因在系统发育上位于颗粒酶、组织蛋白酶G和十二指肠酶之间。因此，这些基因可能是在胎盘哺乳动物与有袋类动物分离之后作为独立的亚家族进化而来的。在鸭嘴兽中，仅能鉴定出一个类似糜蛋白酶位点的序列。这个先前发表的“颗粒酶”与任何糜蛋白酶位点基因家族都没有明显的聚类，但与其他糜蛋白酶位点蛋白酶一样缺乏Cys(191)-Cys(220)桥。这些发现表明，所有糜蛋白酶位点基因都源自一个存在于2亿多年前的共同祖先。
