TY - JOUR

T1 - Hypoosmotic cell swelling as a novel mechanism for modulation of cloned HCN2 channels.

AU - Calloe, Kirstine

AU - Elmedyb, Pernille

AU - Olesen, Søren-Peter

AU - Jorgensen, Nanna K

AU - Grunnet, Morten

N1 - Keywords: Actins; Animals; Cell Shape; Cyclic AMP; Cytochalasin D; Cytoskeleton; DNA, Complementary; Electrophysiology; Globins; Humans; Ion Channels; Ions; KCNQ Potassium Channels; Kinetics; Oocytes; Osmosis; Phalloidine; Time Factors; Xenopus laevis

PY - 2005

Y1 - 2005

N2 - This work demonstrates cell swelling as a new regulatory mechanism for the cloned hyperpolarization-activated, cyclic nucleotide-gated channel 2 (HCN2). HCN2 channels were coexpressed with aquaporin1 in Xenopus laevis oocytes and currents were monitored using a two-electrode voltage-clamp. HCN2 channels were activated by hyperpolarization to -100 mV and the currents were measured before and during hypoosmotic cell swelling. Cell swelling increased HCN2 currents by 30% without changing the kinetics of the currents. Injection of 50 nl intracellular solution resulted in a current increase of 20%, indicating that an increase in cell volume also under isoosmotic conditions may lead to activation of HCN2. In the absence of aquaporin1 only negligible changes in oocyte cell volume occur during exposure to hypoosmotic media and no significant change in HCN2 channel activity was observed during perfusion with hypoosmotic media. This indicates that cell swelling and not a change in ionic strength of the media, caused the observed swelling-induced increase in current. The increase in HCN2 current induced by cell swelling could be abolished by cytochalasin D treatment, indicating that an intact F-actin cytoskeleton is a prerequisite for the swelling-induced current.

AB - This work demonstrates cell swelling as a new regulatory mechanism for the cloned hyperpolarization-activated, cyclic nucleotide-gated channel 2 (HCN2). HCN2 channels were coexpressed with aquaporin1 in Xenopus laevis oocytes and currents were monitored using a two-electrode voltage-clamp. HCN2 channels were activated by hyperpolarization to -100 mV and the currents were measured before and during hypoosmotic cell swelling. Cell swelling increased HCN2 currents by 30% without changing the kinetics of the currents. Injection of 50 nl intracellular solution resulted in a current increase of 20%, indicating that an increase in cell volume also under isoosmotic conditions may lead to activation of HCN2. In the absence of aquaporin1 only negligible changes in oocyte cell volume occur during exposure to hypoosmotic media and no significant change in HCN2 channel activity was observed during perfusion with hypoosmotic media. This indicates that cell swelling and not a change in ionic strength of the media, caused the observed swelling-induced increase in current. The increase in HCN2 current induced by cell swelling could be abolished by cytochalasin D treatment, indicating that an intact F-actin cytoskeleton is a prerequisite for the swelling-induced current.

U2 - 10.1529/biophysj.105.063792

DO - 10.1529/biophysj.105.063792

M3 - Journal article

C2 - 15980171

VL - 89

SP - 2159

EP - 2169

JO - Biophysical Journal

JF - Biophysical Journal

SN - 0006-3495

IS - 3

ER -