Perez-Terzic C, Jaconi M, Clapham D E
Department of Pharmacology, Mayo Foundation, Rochester, MN 55905, USA.
Bioessays. 1997 Sep;19(9):787-92. doi: 10.1002/bies.950190908.
In eukaryotic cells the nucleus and its contents are separated from the cytoplasm by the nuclear envelope. Macromolecules, as well as smaller molecules and ions, can cross the nuclear envelope through the nuclear pore complex. Molecules greater than approx. 60 kDa and containing a nuclear localization signal are actively transported across the nuclear membranes, but there has been little evidence for regulatory mechanisms for smaller molecules and ions. Recently, diffusion across the nuclear envelope has been observed to be regulated by nuclear cisternal Ca2+ concentrations. Following depletion of Ca2+ from the nuclear store by inositol 1,4,5-trisphosphate or Ca2+ chelators, a fluorescent 10 kDa marker molecule was no longer able to enter the nucleus. Distinct conformational states of the nuclear pore complexes depended on the Ca2+ filling state of the nuclear envelope, supporting the assumption that a switch in the conformation of the nuclear pore complex may control the transport of intermediate-sized molecules across the nuclear envelope. Thus nuclear Ca2+ stores may regulate the conformational state of the nuclear pore complex, and thereby passive diffusion of molecules between the cytosol and the nucleoplasm. The physiological significance of this finding is currently unknown.
在真核细胞中，细胞核及其内含物通过核膜与细胞质分隔开来。大分子以及较小的分子和离子可以通过核孔复合体穿过核膜。大于约60 kDa且含有核定位信号的分子会被主动转运穿过核膜，但对于较小的分子和离子的调控机制，几乎没有证据。最近，已观察到穿过核膜的扩散受核池Ca2+浓度的调控。在用肌醇1,4,5-三磷酸或Ca2+螯合剂耗尽核储存中的Ca2+后，一种荧光10 kDa标记分子不再能够进入细胞核。核孔复合体的不同构象状态取决于核膜的Ca2+填充状态，这支持了核孔复合体构象的转变可能控制中等大小分子穿过核膜运输的假设。因此，核Ca2+储存可能调控核孔复合体的构象状态，从而调控分子在细胞质和核质之间的被动扩散。这一发现的生理学意义目前尚不清楚。
