The Kv2.2 alpha subunit contributes to delayed rectifier K(+) currents in myocytes from rabbit corpus cavernosum.
K(+) currents are known to regulate the excitability of corpus cavernosum myocytes and therefore to play a role in the control of penile erection and detumescence. We used electrophysiology and molecular cloning techniques to identify ion channel proteins that contribute to K(+) currents in rabbit cavernosal myocytes. Currents were recorded from freshly isolated myocytes using whole-cell patch clamp techniques. Cavernosal myocytes expressed a delayed rectifier voltage-gated K(+) current that appeared to contribute to the resting membrane potential. This voltage-gated K(+) (K(v)) current was inhibited by the nonselective compounds 4-aminopyridine (1-10 mM), (+)-fenfluramine (10 micro M-1 mM), and Grammostola spatulata venom (1:100) in a dose-dependent and reversible fashion. Hanatoxin-1 (1 micro M), a selective Kv2 channel inhibitor, partially inhibited the current, but alpha-dendrotoxin (200 nM), a Kv1 channel blocker, had no effect. The nucleotide sequence of K(+) channel subunits was determined by polymerase chain reaction-based cloning techniques using RNA derived from cavernosal muscle strips and single identified myocytes. Molecular cloning techniques identified the full-length sequence of the rabbit ortholog of the Kv2.2 alpha subunit. This sequence contains 911 amino acid residues and is 92% identical to the recently revised human Kv2.2 sequence. Identified cavernosal myocytes of the type used in physiological recordings expressed Kv2.2 messenger RNA. We conclude that Kv2.2 alpha subunits contribute to whole-cell currents in rabbit canvernosal myocytes. Further, K(v) currents play a role in regulating membrane potential and hence excitability in rabbit cavernosal myocytes.
Malysz
John
J
Department of Physiology, Mayo Clinic, Rochester, Minnesota 55905, USA.
Farrugia
Gianrico
G
Ou
Yijun
Y
Szurszewski
Joseph H
JH
Nehra
Ajay
A
Gibbons
Simon J
SJ
D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence / Q000235:genetics; D003001:Cloning, Molecular / Q000379:methods; D051668:Delayed Rectifier Potassium Channels; D004553:Electric Conductivity; D008297:Male; D008969:Molecular Sequence Data; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010413:Penis / Q000166:cytology / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D011817:Rabbits; D051669:Shab Potassium Channels
D051668:Delayed Rectifier Potassium Channels; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051669:Shab Potassium Channels