A. Draguhn et al., LARGE-CONDUCTANCE CATION CHANNELS IN THE ENVELOPE OF NUCLEI FROM RAT CEREBRAL-CORTEX, The Journal of membrane biology, 158(2), 1997, pp. 159-166
Eucaryotic nuclei are surrounded by a double-membrane system enclosing
a central cisterna which is continuous with the endoplasmic reticulum
and serves as a calcium store for intracellular signaling. The envelo
pe regulates protein and nucleic acid traffic between the nucleus and
the cytoplasm via nuclear pores. These protein tunnels cross through b
oth nuclear membranes and are permeable for large molecules. Surprisin
gly, patch clamp recordings from isolated nuclei of different cell spe
cies have revealed a high resistance of the envelope, enabling tight s
eals and the resolution of single ion channel activity. Here we presen
t for the first time single-channel recordings from nuclei prepared fr
om neuronal tissue. Nuclei isolated from rat cerebral cortex displayed
spontaneous long-lasting large conductances in the nucleus-attached m
ode as well as in excised patches. The open times are in the range of
seconds and channel activity increases with depolarization. The single
-channel conductance in symmetrical K+ is 166 pS. The channels are sel
ective for cations with P-K/P-Na = 2. They are neither permeable to, n
or gated by Ca2+. Thus, neuronal tissue nuclei contain a large conduct
ance ion channel selective for monovalent cations which may contribute
to ionic homeostasis in the complex compartments surrounding these or
ganelles.