Boldogh I, Vojtov N, Karmon S, Pon L A
Department of Anatomy and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
J Cell Biol. 1998 Jun 15;141(6):1371-81. doi: 10.1083/jcb.141.6.1371.
Transfer of mitochondria to daughter cells during yeast cell division is essential for viable progeny. The actin cytoskeleton is required for this process, potentially as a track to direct mitochondrial movement into the bud. Sedimentation assays reveal two different components required for mitochondria-actin interactions: (1) mitochondrial actin binding protein(s) (mABP), a peripheral mitochondrial outer membrane protein(s) with ATP-sensitive actin binding activity, and (2) a salt-inextractable, presumably integral, membrane protein(s) required for docking of mABP on the organelle. mABP activity is abolished by treatment of mitochondria with high salt. Addition of either the salt-extracted mitochondrial peripheral membrane proteins (SE), or a protein fraction with ATP-sensitive actin-binding activity isolated from SE, to salt-washed mitochondria restores this activity. mABP docking activity is saturable, resistant to high salt, and inhibited by pre-treatment of salt-washed mitochondria with papain. Two integral mitochondrial outer membrane proteins, Mmm1p (Burgess, S.M., M. Delannoy, and R.E. Jensen. 1994. J.Cell Biol. 126:1375-1391) and Mdm10p, (Sogo, L.F., and M.P. Yaffe. 1994. J.Cell Biol. 126:1361- 1373) are required for these actin-mitochondria interactions. Mitochondria isolated from an mmm1-1 temperature-sensitive mutant or from an mdm10 deletion mutant show no mABP activity and no mABP docking activity. Consistent with this, mitochondrial motility in vivo in mmm1-1 and mdm10Delta mutants appears to be actin independent. Depolymerization of F-actin using latrunculin-A results in loss of long-distance, linear movement and a fivefold decrease in the velocity of mitochondrial movement. Mitochondrial motility in mmm1-1 and mdm10Delta mutants is indistinguishable from that in latrunculin-A-treated wild-type cells. We propose that Mmm1p and Mdm10p are required for docking of mABP on the surface of yeast mitochondria and coupling the organelle to the actin cytoskeleton.
酵母细胞分裂过程中线粒体向子细胞的转移对于产生有活力的后代至关重要。肌动蛋白细胞骨架参与了这一过程，可能作为引导线粒体向芽移动的轨道。沉降分析揭示了线粒体与肌动蛋白相互作用所需的两种不同成分：（1）线粒体肌动蛋白结合蛋白（mABP），一种具有ATP敏感性肌动蛋白结合活性的线粒体外膜外周蛋白；（2）一种盐不溶性的、可能是整合的膜蛋白，用于mABP在细胞器上的对接。用高盐处理线粒体可消除mABP活性。向盐洗后的线粒体中添加盐提取的线粒体外周膜蛋白（SE）或从SE中分离出的具有ATP敏感性肌动蛋白结合活性的蛋白组分，可恢复该活性。mABP对接活性具有饱和性，对高盐具有抗性，并且用木瓜蛋白酶预处理盐洗后的线粒体可抑制该活性。两种线粒体外膜整合蛋白，Mmm1p（Burgess, S.M., M. Delannoy, and R.E. Jensen. 1994. J.Cell Biol. 126:1375 - 1391）和Mdm10p（Sogo, L.F., and M.P. Yaffe. 1994. J.Cell Biol. 126:1361 - 1373）参与了这些肌动蛋白与线粒体的相互作用。从mmm1 - 1温度敏感突变体或mdm10缺失突变体中分离出的线粒体没有mABP活性和mABP对接活性。与此一致的是，mmm1 - 1和mdm10Δ突变体体内的线粒体运动似乎不依赖于肌动蛋白。使用拉春库林 - A使F - 肌动蛋白解聚会导致长距离线性运动丧失，线粒体运动速度降低五倍。mmm1 - 1和mdm10Δ突变体中的线粒体运动与用拉春库林 - A处理的野生型细胞中的线粒体运动没有区别。我们认为Mmm1p和Mdm10p是mABP对接在酵母线粒体表面并使细胞器与肌动蛋白细胞骨架偶联所必需的。
