Lane J D, Vergnolle M A, Woodman P G, Allan V J
School of Biological Sciences, University of Manchester, Manchester M13 9PT, United Kingdom.
J Cell Biol. 2001 Jun 25;153(7):1415-26. doi: 10.1083/jcb.153.7.1415.
Cytoplasmic dynein is the major minus end-directed microtubule motor in animal cells, and associates with many of its cargoes in conjunction with the dynactin complex. Interaction between cytoplasmic dynein and dynactin is mediated by the binding of cytoplasmic dynein intermediate chains (CD-IC) to the dynactin subunit, p150(Glued). We have found that both CD-IC and p150(Glued) are cleaved by caspases during apoptosis in cultured mammalian cells and in Xenopus egg extracts. Xenopus CD-IC is rapidly cleaved at a conserved aspartic acid residue adjacent to its NH(2)-terminal p150(Glued) binding domain, resulting in loss of the otherwise intact cytoplasmic dynein complex from membranes. Cleavage of CD-IC and p150(Glued) in apoptotic Xenopus egg extracts causes the cessation of cytoplasmic dynein--driven endoplasmic reticulum movement. Motility of apoptotic membranes is restored by recruitment of intact cytoplasmic dynein and dynactin from control cytosol, or from apoptotic cytosol supplemented with purified cytoplasmic dynein--dynactin, demonstrating the dynamic nature of the association of cytoplasmic dynein and dynactin with their membrane cargo.
胞质动力蛋白是动物细胞中主要的向微管负端移动的分子马达，它与许多货物结合时需要动力蛋白激活蛋白复合物的参与。胞质动力蛋白与动力蛋白激活蛋白之间的相互作用是由胞质动力蛋白中间链（CD-IC）与动力蛋白激活蛋白亚基p150（Glued）的结合介导的。我们发现，在培养的哺乳动物细胞和非洲爪蟾卵提取物的凋亡过程中，CD-IC和p150（Glued）都会被半胱天冬酶切割。非洲爪蟾CD-IC在其氨基末端p150（Glued）结合结构域附近的一个保守天冬氨酸残基处迅速被切割，导致原本完整的胞质动力蛋白复合物从膜上丢失。凋亡的非洲爪蟾卵提取物中CD-IC和p150（Glued）的切割会导致胞质动力蛋白驱动的内质网移动停止。通过从对照胞质溶胶中，或从补充了纯化的胞质动力蛋白-动力蛋白激活蛋白的凋亡胞质溶胶中募集完整的胞质动力蛋白和动力蛋白激活蛋白，凋亡膜的运动性得以恢复，这证明了胞质动力蛋白和动力蛋白激活蛋白与其膜货物结合的动态性质。
