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Evidence for Ca 2+ ‐ and ATP‐sensitive peripheral channels in nuclear pore complexes
Author(s) -
SHAHIN VICTOR,
DANKER TIMM,
ENSS KAROLINE,
OSSIG RAINER,
OBERLEITHNER HANS
Publication year - 2001
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.00-0837fje
Subject(s) - vinculin , focal adhesion , chemistry , adhesion , population , clinostat , integrin , cell adhesion , microbiology and biotechnology , biophysics , cell , biology , biochemistry , organic chemistry , demography , sociology
ABSTRACT In eukaryotic cells the nuclear envelope (NE) serves as a functional barrier between cytosol and nucleoplasm perforated by nuclear pore complexes (NPCs). Both active and passive transport of ions and macromolecules are thought to be mediated by the centrally located large NPC channel. However, 3‐di‐mensional imaging of NPCs based on electron microscopy indicates the existence of additional small channels of unknown function located in the NPC periphery. By means of the recently developed nuclear hourglass technique that measures NE electrical conductance, we evaluated passive electrically driven transport through NPCs. In isolated Xenopus laevis oocyte nuclei, we varied ambient Ca 2+ and ATP in the cytoso‐lic solution and/or chelated Ca 2+ in the perinuclear stores in order to assess the role of Ca 2+ in regulating passive ion transport. We noticed that NE electrical conductance is large under conditions where macro‐molecule permeability is known to be low. In addition, atomic force microscopy applied to native NPCs detects multiple small pores in the NPC periphery consistent with channel openings. Peripheral pores were detectable only in the presence of ATP. We conclude that NPC transport of ions and macromolecules occurs through different routes. We present a model in which NE ion flux does not occur through the central NPC channel but rather through Ca 2+ ‐ and ATP‐activated peripheral channels of individual NPCs.