Functional expression of a GFP-tagged Kv1.5 alpha-subunit in mouse ventricle.
The experiments here were undertaken to determine the feasibility of increasing the cell surface expression of voltage-gated ion channels in cardiac cells in vivo and to explore the functional consequences of ectopic channel expression. Transgenic mice expressing a green fluorescent protein (GFP)-tagged, voltage-gated K+ (Kv) channel alpha-subunit, Kv1.5-GFP, driven by the cardiac-specific alpha-MHC promoter, were generated. In recent studies, Kv1.5 has been shown to encode the micromolar 4-aminopyridine (4-AP)-sensitive delayed rectifier K+ current (I(K,slow)) in mouse myocardium. Unexpectedly, Kv1.5-GFP expression is heterogeneous in the ventricles of these animals. Although no electrocardiographic abnormalities were evident, expression of Kv1.5-GFP results in marked decreases in action potential durations in GFP-positive ventricular myocytes. In voltage-clamp recordings from GFP-positive ventricular myocytes, peak outward K+ currents are significantly higher, and their waveforms are distinct from those recorded from wild-type cells. Pharmacological experiments revealed a selective increase in a micromolar 4-AP-sensitive current, similar to the 4-AP-sensitive component of I(K,slow) in wild-type cells. The inactivation rate of the "overexpressed" current, however, is significantly slower than the Kv1.5-encoded component of I(K,slow) in wild-type cells, suggesting differences in association with accessory subunits and/or posttranslational processing.
Li
H
H
Department of Molecular Biology and Pharmacology, Washington University Medical School, St. Louis, Missouri 63110, USA.
Guo
W
W
Xu
H
H
Hood
R
R
Benedict
A T
AT
Nerbonne
J M
JM
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002478:Cells, Cultured; D015870:Gene Expression / Q000502:physiology; D049452:Green Fluorescent Proteins; D006352:Heart Ventricles / Q000166:cytology; D006801:Humans; D007202:Indicators and Reagents / Q000378:metabolism; D007668:Kidney / Q000166:cytology; D051666:Kv1.5 Potassium Channel; D008164:Luminescent Proteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000502:physiology*; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D011499:Protein Processing, Post-Translational; D014162:Transfection
D007202:Indicators and Reagents; C496981:KCNA5 protein, human; C496982:Kcna5 protein, mouse; D051666:Kv1.5 Potassium Channel; D008164:Luminescent Proteins; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D049452:Green Fluorescent Proteins