Darmon A J, Ehrman N, Caputo A, Fujinaga J, Bleackley R C
Department of Biochemistry, University of Alberta, Edmonton, Canada.
J Biol Chem. 1994 Dec 23;269(51):32043-6.
Murine granzyme B (cytotoxic cell proteinase-1 (CCP1)) is a member of a family of seven serine proteases found in cytoplasmic granules of cytotoxic T lymphocytes (CTLs). Evidence has suggested that it is involved in target cell DNA fragmentation during CTL-mediated cytotoxicity, although intracellular substrates for granzyme B have not yet been identified. The substrate specificity of granzyme B, requiring an aspartic acid residue at site P1, is unique among eukaryotic serine proteases and is shared with only one other known eukaryotic protease, interleukin-1 beta-converting enzyme (ICE). ICE is responsible for processing pro-interleukin-1 beta to produce biologically active interleukin-1 beta and is itself synthesized as an inactive precursor. Recent evidence has suggested a role for ICE in programmed cell death, which led to a model for CTL-mediated cytotoxicity. In this proposal granzyme B activates ICE in the target cell by proteolytically processing the ICE precursor, resulting in active ICE heterodimer that induces apoptosis in the target cell. We have isolated the cDNA encoding murine ICE and generated in vitro translated ICE precursor. Using lysates from COS cells expressing granzyme B we show that ICE precursor is not a substrate for granzyme B and propose an alternate mechanism for CTL-mediated cytotoxicity.
小鼠颗粒酶B（细胞毒性细胞蛋白酶-1（CCP1））是在细胞毒性T淋巴细胞（CTL）胞质颗粒中发现的七种丝氨酸蛋白酶家族的成员。有证据表明，它参与CTL介导的细胞毒性过程中的靶细胞DNA片段化，尽管颗粒酶B的细胞内底物尚未确定。颗粒酶B的底物特异性要求在P1位点有一个天冬氨酸残基，这在真核丝氨酸蛋白酶中是独特的，并且仅与另一种已知的真核蛋白酶白细胞介素-1β转换酶（ICE）相同。ICE负责加工前白细胞介素-1β以产生具有生物活性的白细胞介素-1β，其本身作为无活性前体合成。最近的证据表明ICE在程序性细胞死亡中起作用，这导致了CTL介导的细胞毒性模型。在这个模型中，颗粒酶B通过蛋白水解加工ICE前体在靶细胞中激活ICE，产生诱导靶细胞凋亡的活性ICE异二聚体。我们已经分离出编码小鼠ICE的cDNA并产生了体外翻译的ICE前体。使用表达颗粒酶B的COS细胞裂解物，我们表明ICE前体不是颗粒酶B的底物，并提出了CTL介导的细胞毒性的另一种机制。
