Mitsuyama Fuyuki, Futatsugi Yoshio, Okuya Masato, Karagiozov Kostadin, Kato Yoko, Kanno Tetsuo, Sano Hirotoshi, Koide Tadashi, Sawai Tsuyosi
Department of Neurosurgery, Fujita Health University, Toyoake, Aichi, Japan.
Ital J Anat Embryol. 2008 Jul-Sep;113(3):143-51.
It has been reported that F-actin is transported to the presumptive cleavage furrow along the cortex during anaphase-cytokinesis, an event termed cortical actin flow in animal cultured cells. The motor source has remained unknown. We reported that Ca2+ stores with IP3 receptor (IP3R) was re-distributed from the polar cortex during metaphase to the presumptive cleavage furrow just before the onset of furrowing, and that Ca2+ stores with IP3R microinjected into dividing newt eggs moved toward the presumptive cleavage furrow during anaphase-cytokinesis in a microtubule-dependent manner, and that Ca2+ store-enriched microsome fractions induced the cleavage furrow as the putative cleavage stimulus. Because the distribution of F-actin and Ca2+ stores with IP3R during metaphase to cytokinesis is similar, we considered that this cortical actin flow may be powered by transportation of Ca2+ stores with IP3R. Purified F-actin labeled with phalloidin-rhodamine was microinjected into the dividing newt eggs and the eggs observed under a confocal microscope. We found that the microinjected F-actin moved linearly toward the next cleavage furrow and that this movement was blocked by nocodazole, microtubule-depolarizing agent and AMP-PNP, a blocking agent of microtubule motors. Co-microinjected rhodamine-labeled F-actin and sacro/endoplasmic reticulum Ca2+-ATPase (SERCA)-GFP-labeled Ca2+ stores with IP3R co-moved and co-accumulated to the next cleavage furrow. These results strongly suggest that Ca2+ stores with IP3R, which is transferred by microtubule-based motility as cleavage stimulus, act as an F-actin translocator.
据报道，在后期胞质分裂过程中，F-肌动蛋白沿着皮质被运输到假定的分裂沟，这一事件在动物培养细胞中被称为皮质肌动蛋白流。其动力来源一直未知。我们报道过，含有IP3受体（IP3R）的Ca2+储存库在中期从极性皮质重新分布到即将开始缢缩前的假定分裂沟，并且微注射到分裂蝾螈卵中的含有IP3R的Ca2+储存库在后期胞质分裂期间以微管依赖的方式向假定分裂沟移动，而且富含Ca2+储存库的微粒体组分作为假定的分裂刺激诱导了分裂沟的形成。由于中期到胞质分裂期间F-肌动蛋白和含有IP3R的Ca2+储存库的分布相似，我们认为这种皮质肌动蛋白流可能由含有IP3R的Ca2+储存库的运输提供动力。将用鬼笔环肽-罗丹明标记的纯化F-肌动蛋白微注射到分裂的蝾螈卵中，并在共聚焦显微镜下观察这些卵。我们发现微注射的F-肌动蛋白线性地朝着下一个分裂沟移动，并且这种移动被诺考达唑（一种微管去极化剂）和微管马达阻断剂AMP-PNP所阻断。共微注射罗丹明标记的F-肌动蛋白和用肌浆/内质网Ca2+-ATP酶（SERCA）-绿色荧光蛋白标记的含有IP3R的Ca2+储存库共同移动并共同积累到下一个分裂沟。这些结果有力地表明，含有IP3R的Ca2+储存库作为F-肌动蛋白转运体，它作为分裂刺激通过基于微管的运动而转移。
