Biophys J, July 2000, p. 202-214, Vol. 79, No. 1

Distinct Ion Channel Classes Are Expressed on the Outer Nuclear Envelope of T- and B-Lymphocyte Cell Lines

Alfredo Franco-Obregón,^* Hong-wei Wang, and David E. Clapham

 ^*Solid State Physics Laboratory, ETH Zurich, CH 8093 Zurich, Switzerland, and  Department of Basic Cardiovascular Research, Howard Hughes Medical Institute, Children's Hospital/Harvard Medical School, Boston, Massachusetts 02115 USA

The outer nuclear membrane, endoplasmic reticulum, and mitochondrial membrane ion channels are poorly understood, although they are important in the control of compartmental calcium levels, cell division, and apoptosis. Few direct recordings of these ion channels have been made because of the difficulty of accessing these intracellular membranes. Using patch-clamp techniques on isolated nuclei, we measured distinct ion channel classes on the outer nuclear envelope of T-cell (human Jurkat) and BFL5 cell (murine promyelocyte) lines. We first imaged the nuclear envelopes of both Jurkat and FL5 cells with atomic force microscopy to determine the density of pore proteins. The nuclear pore complex was intact at roughly similar densities in both cell types. In patch-clamp recordings of Jurkat nuclear membranes, Cl channels (105 ± 5 pS) predominated and inactivated with negative pipette potentials. Nucleotides transiently inhibited the anion channel. In contrast, FL5 nuclear channels were cation selective (52 ± 2 pS), were inactivated with positive membrane potentials, and were insensitive to GTPS applied to the bath. We hypothesize that T- and B-cell nuclear membrane channels are distinct, and that this is perhaps related to their unique roles in the immune system.

Biophys J, July 2000, p. 202-214, Vol. 79, No. 1
© 2000 by the Biophysical Society   0006-3495/00/07/202/13  $2.00

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