A Novel Large Conductance, Nonselective Cation Channel in Pheochromocytoma (PC12) Cells

A Novel Large Conductance, Nonselective Cation Channel in Pheochromocytoma (PC12) Cells A new type of nonselective cation channel was identified and characterized in pheochromocytoma (PC12) cells using inside-out and cell-attached patch-clamp recordings. The channel shows a large unitary conductance (274 pS in symmetric 145 mm K+) and selectivity for Na+≈ K+ > Li+, and is practically impermeable to Cl−. The channel activity-voltage relationship is bell-shaped, showing maximal activation at ≈−10 mV. The overall activity of this channel is unmodified by [Na+] ic , or [Ca++] ic . However, increases in [Ca++] ic lead to a decrease in the unitary current amplitude. In addition, overall activity is mildly increased when suction is applied to the back of the patch pipette. Together, these characteristics distinguish the present channel from all other large conductance nonselective cation channels reported so far in a variety of preparations. The frequency of appearance of this channel type is similar in undifferentiated and NGF-treated PC12 cells (≈8–27% of patches). The combination of large conductance, permeability to Na+, and existence of conducting states at negative potentials, may provide a significant pathway for inward current and depolarization in PC12 cells. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

A Novel Large Conductance, Nonselective Cation Channel in Pheochromocytoma (PC12) Cells

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 1997 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900304
Publisher site
See Article on Publisher Site

Abstract

A new type of nonselective cation channel was identified and characterized in pheochromocytoma (PC12) cells using inside-out and cell-attached patch-clamp recordings. The channel shows a large unitary conductance (274 pS in symmetric 145 mm K+) and selectivity for Na+≈ K+ > Li+, and is practically impermeable to Cl−. The channel activity-voltage relationship is bell-shaped, showing maximal activation at ≈−10 mV. The overall activity of this channel is unmodified by [Na+] ic , or [Ca++] ic . However, increases in [Ca++] ic lead to a decrease in the unitary current amplitude. In addition, overall activity is mildly increased when suction is applied to the back of the patch pipette. Together, these characteristics distinguish the present channel from all other large conductance nonselective cation channels reported so far in a variety of preparations. The frequency of appearance of this channel type is similar in undifferentiated and NGF-treated PC12 cells (≈8–27% of patches). The combination of large conductance, permeability to Na+, and existence of conducting states at negative potentials, may provide a significant pathway for inward current and depolarization in PC12 cells.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Nov 15, 1997

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