Shresta S, Goda P, Wesselschmidt R, Ley T J
Department of Internal Medicine, Washington University School of Medicine, Campus Box 8007, St. Louis, Missouri 63110-1093, USA.
J Biol Chem. 1997 Aug 8;272(32):20236-44. doi: 10.1074/jbc.272.32.20236.
Cytotoxic lymphocytes contain granules that have the ability to induce apoptosis in susceptible target cells. The granule contents include perforin, a pore-forming molecule, and several granzymes, including A and B, which are the most abundant serine proteases in these granules. Granzyme B-deficient cytotoxic T lymphocytes (CTL) have a severe defect in their ability to rapidly induce apoptosis in their targets, but have an intact late cytotoxicity pathway that is in part perforin-dependent. In this report, we have created mice that are deficient for granzyme A and characterized their phenotype. These mice have normal growth and development and normal lymphocyte development, activation, and proliferation. Granzyme A-deficient CTL have a small but reproducible defect in their ability to induce 51Cr and 125I-UdR release from susceptible allogeneic target cells. Since other granzyme A-like tryptases could potentially account for the residual cytotoxicity in granzyme A-deficient CTL, we cloned the murine granzyme K gene, which is linked to granzyme A in humans, and proved that it is also tightly linked with murine granzyme A. The murine granzyme K gene (which encodes a tryptase similar to granzyme A) is expressed at much lower levels than granzyme A in CTL and LAK cells, but its expression is unaltered in granzyme A-/- mice. The minimal cytotoxic defect in granzyme A-/- CTL could be due to the existence of an intact, functional early killing pathway (granzyme B dependent), or to the persistent expression of additional granzyme tryptases like granzyme K.
细胞毒性淋巴细胞含有能够诱导易感靶细胞凋亡的颗粒。颗粒内容物包括穿孔素，一种形成孔道的分子，以及几种颗粒酶，包括A和B，它们是这些颗粒中最丰富的丝氨酸蛋白酶。颗粒酶B缺陷的细胞毒性T淋巴细胞（CTL）在快速诱导靶细胞凋亡的能力方面存在严重缺陷，但具有完整的晚期细胞毒性途径，该途径部分依赖于穿孔素。在本报告中，我们创建了颗粒酶A缺陷的小鼠并对其表型进行了表征。这些小鼠生长发育正常，淋巴细胞发育、激活和增殖也正常。颗粒酶A缺陷的CTL在诱导易感同种异体靶细胞释放51Cr和125I-UdR的能力方面存在微小但可重复的缺陷。由于其他颗粒酶A样类胰蛋白酶可能解释颗粒酶A缺陷的CTL中的残余细胞毒性，我们克隆了小鼠颗粒酶K基因，其在人类中与颗粒酶A连锁，并证明它也与小鼠颗粒酶A紧密连锁。小鼠颗粒酶K基因（编码一种类似于颗粒酶A的类胰蛋白酶）在CTL和LAK细胞中的表达水平远低于颗粒酶A，但其在颗粒酶A - / - 小鼠中的表达未改变。颗粒酶A - / - CTL中最小的细胞毒性缺陷可能是由于存在完整的、功能性的早期杀伤途径（依赖颗粒酶B），或者是由于额外的颗粒酶类胰蛋白酶如颗粒酶K的持续表达。
