Quarmby L M, Lohret T A
Department of Cell Biology, Emory University, Atlanta, Georgia 30322-3030, USA.
Cell Motil Cytoskeleton. 1999;43(1):1-9. doi: 10.1002/(SICI)1097-0169(1999)43:1<1::AID-CM1>3.0.CO;2-#.
The regulation of microtubule stability by severing of the polymer along its length is a newly appreciated and potentially important mechanism for controlling microtubule function. Microtubule severing occurs in living cells, but direct observation of this event is infrequent. The paucity of direct observations leave open to question the significance of regulated microtubule severing in the control of microtubule organization. Nevertheless, several lines of evidence suggest that microtubule severing is an important cellular activity. First, the ATP-dependent microtubule-severing activity of katanin is well documented. Katanin is found in most cell types and is enriched at MTOCs. Although it is possible that katanin does not sever microtubules in vivo, this seems unlikely. Second, a physiological event, deflagellation, has been shown to depend on microtubule severing. The deflagellation system of Chlamydomonas has provided a genetic approach to the problem of microtubule severing. The FA genes are essential for the regulated severing of axonemal microtubules during deflagellation, but whether these genes define new severing proteins or whether they are important for katanin activity remains to be determined. Microtubule severing is a relatively new area of investigation and there are still many more questions than answers. It is anticipated that the recent cloning of katanin and the introduction of a genetic model system will soon lead to significant breakthroughs in this problem.
通过沿微管聚合物长度进行切割来调节微管稳定性，是一种新认识到的且可能对控制微管功能具有重要意义的机制。微管切割发生在活细胞中，但对这一事件的直接观察并不常见。直接观察的匮乏使得微管切割调控在微管组织控制中的重要性存疑。然而，几条证据线索表明微管切割是一项重要的细胞活动。首先，katanin的ATP依赖性微管切割活性已有充分记载。katanin存在于大多数细胞类型中，并在微管组织中心富集。虽然katanin在体内可能不会切割微管，但这种可能性似乎不大。其次，已证明一种生理事件——鞭毛去除，依赖于微管切割。衣藻的鞭毛去除系统为微管切割问题提供了一种遗传学方法。FA基因对于鞭毛去除过程中轴丝微管的调控切割至关重要，但这些基因是定义了新的切割蛋白，还是对katanin活性很重要，仍有待确定。微管切割是一个相对较新的研究领域，问题仍然远多于答案。预计最近katanin的克隆以及遗传模型系统的引入将很快在这个问题上取得重大突破。
