Schauss Astrid C, Bewersdorf Jörg, Jakobs Stefan
Max-Planck Institute for Biophysical Chemistry, Department of NanoBiophotonics, Am Fassberg 11, 37077 Göttingen, Germany.
J Cell Sci. 2006 Aug 1;119(Pt 15):3098-106. doi: 10.1242/jcs.03026. Epub 2006 Jul 11.
The mitochondrial division machinery consists of the large dynamin-related protein Dnm1p (Drp1/Dlp1 in humans), and Fis1p, Mdv1p and Caf4p. Proper assembly of Dnm1p complexes on the mitochondrial surface is crucial for balanced fission and fusion events. Using quantitative confocal microscopy, we show that Caf4p is important for the recruitment of Dnm1p to the mitochondria. The mitochondrial Dnm1p assemblies can be divided into at least two morphologically distinguishable fractions. A small subset of these assemblies appear to be present as Dnm1p-spirals (or rings) that encircle tubule constrictions, with seldom more than seven turns. A larger fraction of the Dnm1p assemblies is primarily present at one side of the mitochondrial tubules. We show that a majority of these mitochondria-associated Dnm1p clusters point towards the cell cortex. This polarized orientation is abolished in fis1Delta and caf4Delta yeast cells, but is maintained in mdv1Delta cells and after disruption of the actin cytoskeleton. This study suggests that Caf4p plays a key role in determining the polarized localization of those Dnm1p clusters that are not immediately involved in the mitochondrial fission process.
线粒体分裂机制由大型动力蛋白相关蛋白Dnm1p(人类中的Drp1/Dlp1)以及Fis1p、Mdv1p和Caf4p组成。Dnm1p复合物在线粒体表面的正确组装对于平衡的裂变和融合事件至关重要。利用定量共聚焦显微镜,我们发现Caf4p对于将Dnm1p招募到线粒体至关重要。线粒体Dnm1p组装体可分为至少两个形态上可区分的部分。这些组装体中的一小部分似乎以Dnm1p螺旋(或环)的形式存在,环绕着小管收缩处,很少有超过七圈的。更大比例的Dnm1p组装体主要存在于线粒体小管的一侧。我们发现,这些与线粒体相关的Dnm1p簇中的大多数指向细胞皮层。在fis1Δ和caf4Δ酵母细胞中,这种极化方向被消除,但在mdv1Δ细胞中以及肌动蛋白细胞骨架破坏后仍保持。这项研究表明,Caf4p在确定那些未立即参与线粒体分裂过程的Dnm1p簇的极化定位中起关键作用。