The regulation of nuclear membrane permeability by Ca2+ signaling: a tightly regulated pore or a floodgate?
The nuclear pore complex functions both to separate and to connect the nucleus and the cytoplasm. Minute-to-minute changes in gene expression depend on rapid translocation of transcription factors and other regulatory proteins from the cytosol into the nucleus. However, a controversy exists as to whether cell signaling allows large molecules to enter the nucleus through tightly regulated facilitated transport or by the opening of a floodgate. A recent report suggesting that some hormones increase nuclear permeability through changes in intracellular Ca(2+) concentration has reignited this debate. Here, I consider both the basic permeability of the nuclear membrane under resting conditions and the effects of Ca(2+) on the permeability of the nuclear pore. I discuss facilitated transport through the nuclear pore complex, with particular attention to the nuclear transport of Ca(2+)-CaM signaling complexes. Finally, I weigh the arguments in favor of a generic increase in permeability versus stimulation of facilitated transport as possible mechanisms for mediating cell signaling to the nucleus.
Török
Katalin
K
Department of Basic Medical Sciences, St George's, University of London, London, UK. ktorok@sgul.ac.uk
D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D004058:Diffusion; D005786:Gene Expression Regulation / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D022022:Nuclear Pore / Q000378:metabolism*; D010539:Permeability; D015398:Signal Transduction / Q000502:physiology*
D049452:Green Fluorescent Proteins; D002118:Calcium