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Aldosterone signaling pathway across the nuclear envelope
C Schäfer1, V Shahin, L Albermann
1Institute of Physiology, University of Münster, D-48149 Münster, Germany.
Summary
Aldosterone triggers macromolecule movement through Xenopus oocyte nuclear pores. This process, involving nuclear pore complexes (NPCs), can be measured electrically and used to identify early genes.
Area of Science:
- Cell Biology
- Molecular Endocrinology
- Xenopus laevis Oocyte Research
Background:
- Aldosterone initiates genomic responses.
- Understanding macromolecule transport through the nuclear envelope is crucial.
Purpose of the Study:
- To elucidate the pathway of aldosterone-triggered macromolecules entering and exiting the Xenopus oocyte nucleus.
- To investigate aldosterone-induced conformational changes in nuclear pore complexes (NPCs).
Main Methods:
- Microinjection of aldosterone into Xenopus oocytes.
- Measurement of nuclear envelope electrical resistance (NEER) using the nuclear hourglass technique.
- Atomic force microscopy (AFM) to observe NPC conformational changes.
Main Results:
- Three distinct NEER stages were observed, correlating with molecular events at NPCs.
- Small molecules ('flags') attached to NPCs early, followed by larger molecules ('plugs') within NPC channels.
- Spironolactone blocked aldosterone-induced electrical changes and molecular events; RNase/ActD prevented the late NEER peak.
Conclusions:
- Aldosterone's genomic response is electrically measurable in oocyte nuclei.
- 'Flags' are likely aldosterone receptors entering the nucleus; 'plugs' are ribonucleoproteins exporting aldosterone-induced mRNA.
- Oocytes can serve as a bioassay for identifying aldosterone-induced early genes.