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Cell Biology International (1997) 21, 747–757 (Printed in Great Britain)
USING ATOMIC FORCE MICROSCOPY TO INVESTIGATE PATCH-CLAMPED NUCLEAR MEMBRANE
TIMM DANKERaf1, MICHELE MAZZANTIb, RAFFAELLA TONINIb, AGNIESZKA RAKOWSKAa and HANS OBERLEITHNERa
aPhysiologisches Institut, Röntgenring 9, Würzburg, Germany
bDipartimento di Fisiologica e Biochimica Generali, Universitá degli Studi di Milano, Italy


Abstract

Nuclear patch clamp is an emerging research field that aims to disclose the electrical phenomena underlying macromolecular transport across the nuclear envelope (NE), its properties as an ion barrier and its function as an intracellular calcium store. The authors combined the patch clamp technique with atomic force microscopy (AFM) to investigate the structure–function relationship of NE. In principle, patch clamp currents, recorded from the NE can indicate the activity of the nuclear pore complexes (NPCs) and/or of ion channels in the two biomembranes that compose the NE. However, the role of the NPCs is still unclear because the observed NE current in patch clamp experiments is lower than expected from the known density of the NPCs. Therefore, AFM was applied to link patch clamp currents to structure. The membrane patch was excised from the nuclear envelope and, after electrical evaluation, transferred from the patch pipette to a substrate. We could identify the native nuclear membrane patches with AFM at a lateral and a vertical resolution of 3nm and 0.1nm, respectively. It was shown that complete NE together with NPCs can be excised from the nucleus after their functional identification in patch clamp experiments. However, we also show that membranes of the endoplasmic reticulum can contaminate the tip of the patch pipette during nuclear patch clamp experiments. This possibility must be considered carefully in nuclear patch clamp experiments.


Key words: nucleus, nuclear envelope, nuclear pore complex, patch clamp technique, atomic force microscope.

f1To whom correspondence should be addressed: Timm Danker, Physiologisches Institut, Röntgenring 9, D-97070 Würzburg, Germany.


doi:10.1006/cbir.1997.0219


ISSN Print: 1065-6995
ISSN Electronic: 1095-8355
Published by Portland Press Limited on behalf of the International Federation for Cell Biology (IFCB)