HCN2 Channels: A Permanent Open State and Conductance Changes

HCN2 Channels: A Permanent Open State and Conductance Changes Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in the membranes of heart and brain cells can conduct Na+ and K+ ions and activate between −30 and −120 mV. We express the α subunit of HCN2 channels in Xenopus laevis oocytes and are confronted with two unexpected problems. First, we observe a rise in membrane conductance at resting potential proportional to the amount of expression. On activation to hyperpolarizing potentials, the instantaneous conductance rises in proportion to the amount of activated current. CsCl reduces the observed effects. This can be explained by the expression in oocytes membranes of a fraction of permanently open HCN2 channels. Second, using TEVC technique, our data show a completely different behaviour in physiological solutions of heterogeneously expressed HCN2 currents from what is observed in wild-type currents in the absence of drugs. During pulse trains, we frequently observe (1) a fast and significant decline of the amplitude of HCN2 current during hyperpolarizing steps, (2) no recovery of this decline after a long period at resting membrane potential, (3) a different behaviour of the tail currents at depolarization with other and slower changes than during activation, (4) recovery of this decline in high K+/low Na+ bath solution. The decline of the HCN2 current in physiological conditions is caused by a reduction of the conductance of the HCN2 channel presumably caused by the mere presence of sodium in the channel, in competition with potassium ions and with a limitative effect on the channel conductance. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

HCN2 Channels: A Permanent Open State and Conductance Changes

Loading next page...
 
/lp/springer_journal/hcn2-channels-a-permanent-open-state-and-conductance-changes-9gTzf1NJbb
Publisher
Springer US
Copyright
Copyright © 2014 by Springer Science+Business Media New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-014-9742-0
Publisher site
See Article on Publisher Site

Abstract

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in the membranes of heart and brain cells can conduct Na+ and K+ ions and activate between −30 and −120 mV. We express the α subunit of HCN2 channels in Xenopus laevis oocytes and are confronted with two unexpected problems. First, we observe a rise in membrane conductance at resting potential proportional to the amount of expression. On activation to hyperpolarizing potentials, the instantaneous conductance rises in proportion to the amount of activated current. CsCl reduces the observed effects. This can be explained by the expression in oocytes membranes of a fraction of permanently open HCN2 channels. Second, using TEVC technique, our data show a completely different behaviour in physiological solutions of heterogeneously expressed HCN2 currents from what is observed in wild-type currents in the absence of drugs. During pulse trains, we frequently observe (1) a fast and significant decline of the amplitude of HCN2 current during hyperpolarizing steps, (2) no recovery of this decline after a long period at resting membrane potential, (3) a different behaviour of the tail currents at depolarization with other and slower changes than during activation, (4) recovery of this decline in high K+/low Na+ bath solution. The decline of the HCN2 current in physiological conditions is caused by a reduction of the conductance of the HCN2 channel presumably caused by the mere presence of sodium in the channel, in competition with potassium ions and with a limitative effect on the channel conductance.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Nov 13, 2014

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off