Yang Weidong, Musser Siegfried M
Department of Molecular and Cellular Medicine, The Texas A&M University System Health Science Center, College Station, TX 77843, USA.
J Cell Biol. 2006 Sep 25;174(7):951-61. doi: 10.1083/jcb.200605053. Epub 2006 Sep 18.
Although many components and reaction steps necessary for bidirectional transport across the nuclear envelope (NE) have been characterized, the mechanism and control of cargo migration through nuclear pore complexes (NPCs) remain poorly understood. Single-molecule fluorescence microscopy was used to track the movement of cargos before, during, and after their interactions with NPCs. At low importin beta concentrations, about half of the signal-dependent cargos that interacted with an NPC were translocated across the NE, indicating a nuclear import efficiency of approximately 50%. At high importin beta concentrations, the import efficiency increased to approximately 80% and the transit speed increased approximately sevenfold. The transit speed and import efficiency of a signal-independent cargo was also increased by high importin beta concentrations. These results demonstrate that maximum nucleocytoplasmic transport velocities can be modulated by at least approximately 10-fold by the importin beta concentration and therefore suggest a potential mechanism for regulating the speed of cargo traffic across the NE.
尽管双向跨核膜（NE）运输所需的许多组件和反应步骤已得到表征，但货物通过核孔复合体（NPC）迁移的机制和调控仍知之甚少。单分子荧光显微镜用于追踪货物与NPC相互作用之前、期间和之后的运动。在低输入蛋白β浓度下，与NPC相互作用的约一半信号依赖性货物穿过NE进行转运，表明核输入效率约为50%。在高输入蛋白β浓度下，输入效率提高到约80%，转运速度提高约7倍。高输入蛋白β浓度也提高了信号非依赖性货物的转运速度和输入效率。这些结果表明，输入蛋白β浓度可将最大核质运输速度调节至少约10倍，因此提示了一种调节货物跨NE运输速度的潜在机制。
