Calcium signals can freely cross the nuclear envelope in hippocampal neurons: somatic calcium increases generate nuclear calcium transients.
BACKGROUND
In hippocampal neurons, nuclear calcium signaling is important for learning- and neuronal survival-associated gene expression. However, it is unknown whether calcium signals generated by neuronal activity at the cell membrane and propagated to the soma can unrestrictedly cross the nuclear envelope to invade the nucleus. The nuclear envelope, which allows ion transit via the nuclear pore complex, may represent a barrier for calcium and has been suggested to insulate the nucleus from activity-induced cytoplasmic calcium transients in some cell types.


RESULTS
Using laser-assisted uncaging of caged calcium compounds in defined sub-cellular domains, we show here that the nuclear compartment border does not represent a barrier for calcium signals in hippocampal neurons. Although passive diffusion of molecules between the cytosol and the nucleoplasm may be modulated through changes in conformational state of the nuclear pore complex, we found no evidence for a gating mechanism for calcium movement across the nuclear border.


CONCLUSIONS
Thus, the nuclear envelope does not spatially restrict calcium transients to the somatic cytosol but allows calcium signals to freely enter the cell nucleus to trigger genomic events.
Department of Neurobiology, Interdisciplinary Centre for Neurosciences, Im Neuenheimer Feld 364, 69120 Heidelberg, Germany. anja.eder@uni-hd.de
Anja
A
Eder
Hilmar
H
Bading
D000818:Animals; D000831:Animals, Newborn; D001640:Bicuculline / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D004533:Egtazic Acid / Q000031:analogs & derivatives; D018756:GABA Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology*; D009474:Neurons / Q000648:ultrastructure*; D009685:Nuclear Envelope / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D018756:GABA Antagonists; C085112:2-nitrophenyl-EGTA; D004533:Egtazic Acid; D002118:Calcium; D001640:Bicuculline