Microtubule regulation by small molecules.

天然产物历来是大多数微管（MT）靶向小分子的来源，其特性使它们成为有用的药物。我们在这项研究中使用的大部分化合物都是如此，但不是全部。这些包括临床建立的mt活性药物秋水仙碱、康布他汀、长春新碱、紫杉醇等。几乎所有这些药物都是首先在临床前研究中开发出来的，包括化合物对微管蛋白聚合的影响的体外研究，以及这些化合物对细胞行为的影响，特别是通过对构成有丝分裂纺锤体的MT阵列的影响来检测化合物破坏有丝分裂的能力。事实上，在实验室中，在快速生长的细胞培养物中引起有丝分裂停止的能力通常被认为是这些药物的主要机制的一种测定方法。

Natural products have historically been the source of most of the microtubule (MT)-targeting small molecules whose properties have allowed them to become useful drugs. That remains true of most but not all of the compounds that we have used in this study. These include the clinically established MT-active drugs colchicine, combretastatin, vincristine, taxol, and others. Almost all such agents were developed first in pre-clinical research that included in vitro studies of the effect of the compounds on polymerization of tubulin to microtubules as well as the effect of such compounds on cell behavior, especially examining the ability of the compounds to disrupt mitosis through effects on the MT arrays that comprise the mitotic spindle. Indeed the ability to cause mitotic arrest in rapidly growing cell cultures in the laboratory is often considered to be an assay of the principal mechanism of these drugs. Nonetheless we have argued that mitosis is not the central target of these drugs in patient tumors. Human tumors grow very slowly compared to laboratory cultures and mitosis is rare, and therefore is not an abundant target. Microtubules are abundant in non-mitotic as well as mitotic cells, however, and hence we have explored the nature of the microtubule functions that these drugs do target. One of those is intracellular transport, which occurs constantly, throughout the cell cycle, and which is required for many central parts of cell metabolism. This traffic is directional and requires the array of organized microtubules to coordinate the process. One aspect of this is the requirement of directional transport to move enzymes from the cytoplasm to the nucleus in response to DNA damage. This occurs on microtubules, and is disrupted by anti-microtubule drugs. We discovered that this interference with DNA repair processes underlies the well-verified potentiation by microtubule-targeting drugs of the anti-cancer activity of DNA-damaging chemotherapy. This insight may allow better scheduling of therapy and rational development of new therapeutic drug combinations. Additionally we have found that tubulin and microtubules have important roles in the regulation of cell oxidative metabolism through interaction with mitochondria. It has been often reported that microtubule-targeting drugs cause release of bursts of reactive oxygen species. These oxidative bursts result in production of carbonyl residues on cellular proteins. In order to study thus better, we have developed a new fluorescent reporter molecule which reacts covalently with carbonyl residues in cellular macromolecules. This allows the quantitation of oxidative events, the imaging of the distribution of these events in the cell, and potentially the isolation of the oxidized macromolecules (through pull-down experiments).