Adult alveolar epithelial cells express multiple subtypes of voltage-gated K+
channels that are located in apical membrane.
Lee, So Yeong, Peter J. Maniak, David H. Ingbar, and Scott M. O'Grady.
1Departments of Physiology and Animal Science and 2Molecular Veterinary
Biosciences Graduate Program, University of Minnesota, St. Paul 55108; and
3Department of Medicine, University of Minnesota, Minneapolis, Minnesota 55455
APStracts 10:0076C, 2003.
Whole cell perforated patch-clamp experiments were performed with adult rat alveolar
epithelial cells. The holding potential was «minus»60 mV, and depolarizing voltage steps
activated voltage-gated K+ (Kv) channels. The voltage-activated currents exhibited a
mean reversal potential of «minus»32 mV. Complete activation was achieved at
«minus»10 mV. The currents exhibited slow inactivation, with significant variability in
the time course between cells. Tail current analysis revealed cell-to-cell variability in K+
selectivity suggesting contributions of multiple Kv a-subunits to the whole cell current.
The Kv channels also displayed steady-state inactivation when the membrane potential
was held at depolarized voltages with a window current between «minus»30 and 5 mV.
Analysis of RNA isolated from these cells by RT-PCR revealed the presence of eight Kv
a-subunits (Kv1.1, Kv1.3, Kv1.4, Kv2.2, Kv4.1, Kv4.2, Kv4.3, and Kv9.3), three ß-
subunits (Kvß1.1, Kvß2.1, and Kvß3.1), and two K+ channel interacting protein (KChIP)
isoforms (KChIP2 and KChIP3). Western blot analysis with available Kv a-subunit
antibodies (Kv1.1, Kv1.3, Kv1.4, Kv4.2, and Kv4.3) showed labeling of 50-kDa proteins
from alveolar epithelial cells grown in monolayer culture. Immunocytochemical analysis
of cells from monolayers showed that Kv1.1, Kv1.3, Kv1.4, Kv4.2, and Kv4.3 were
localized to the apical membrane. We conclude that expression of multiple Kv a-, ß-, and
KChIP subunits explains the variability in inactivation gating and K+ selectivity observed
between cells and that Kv channels in the apical membrane may contribute to basal K+
secretion across the alveolar epithelium.
Received 18 September 2002; accepted in final form 18 February 2003
APS Manuscript Number C429-2.
Article publication pending Am J Physiol Cell Physiol
ISSN 1080-4757 Copyright 2003 The American Physiological Society.
Published in APStracts on 25 March 2003