Journal
JOURNAL OF MEMBRANE BIOLOGY
Volume 187, Issue 2, Pages 97-115Publisher
SPRINGER-VERLAG
DOI: 10.1007/s00232-001-0155-5
Keywords
nuclear envelope; Na,K-ATPase isoforms; immunocytochemistry; sodium green-dextran; SBFI-am; PBFI-am
Funding
- NEI NIH HHS [EY07010] Funding Source: Medline
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Evidence is emerging that the nuclear envelope itself is responsible for transport and signaling activities quite distinct from those associated with the nuclear pore. For example, the envelope has a Ca2+-signaling pathway that, among other things, regulates meiosis in oocytes. The nuclear envelope's outer membrane also contains K+ channels. Here we show that Na+/K+ gradients exist between the nuclear envelope lumen and both cytoplasm and nucleoplasm in hepatocyte nuclei. The gradients are formed by Na,K-ATPases in the envelope's inner membrane, oriented with the ATP hydrolysis site in the nucleoplasm. We further demonstrate nucleoplasm/cytoplasm Na+ and K+ gradients, of which only the Na+-gradient is dissipated directly by Na,K-ATPase inhibition with ouabain. Finally, our results demonstrate that nuclear pores are not freely permeable to sodium and potassium. Based on these results and numerous in vitro studies, nuclear monovalent cation transporters and channels are likely to play a role in modulation of chromatin structure and gene expression.
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