Kv1.5 is a major component underlying the A-type potassium current in retinal arteriolar smooth muscle
Open Access
- 1 February 2007
- journal article
- research article
- Published by American Physiological Society in American Journal of Physiology-Heart and Circulatory Physiology
- Vol. 292 (2), H1001-H1008
- https://doi.org/10.1152/ajpheart.01003.2006
Abstract
Little is known about the molecular characteristics of the voltage-activated K+ (Kv) channels that underlie the A-type K+ current in vascular smooth muscle cells of the systemic circulation. We investigated the molecular identity of the A-type K+ current in retinal arteriolar myocytes using patch-clamp techniques, RT-PCR, immunohistochemistry, and neutralizing antibody studies. The A-type K+ current was resistant to the actions of specific inhibitors for Kv3 and Kv4 channels but was blocked by the Kv1 antagonist correolide. No effects were observed with pharmacological agents against Kv1.1/2/3/6 and 7 channels, but the current was partially blocked by riluzole, a Kv1.4 and Kv1.5 inhibitor. The current was not altered by the removal of extracellular K+ but was abolished by flecainide, indicative of Kv1.5 rather than Kv1.4 channels. Transcripts encoding Kv1.5 and not Kv1.4 were identified in freshly isolated retinal arterioles. Immunofluorescence labeling confirmed a lack of Kv1.4 expression and revealed Kv1.5 to be localized to the plasma membrane of the arteriolar smooth muscle cells. Anti-Kv1.5 antibody applied intracellularly inhibited the A-type K+ current, whereas anti-Kv1.4 antibody had no effect. Co-expression of Kv1.5 with Kvβ1 or Kvβ3 accessory subunits is known to transform Kv1.5 currents from delayed rectifers into A-type currents. Kvβ1 mRNA expression was detected in retinal arterioles, but Kvβ3 was not observed. Kvβ1 immunofluorescence was detected on the plasma membrane of retinal arteriolar myocytes. The findings of this study suggest that Kv1.5, most likely co-assembled with Kvβ1 subunits, comprises a major component underlying the A-type K+ current in retinal arteriolar smooth muscle cells.Keywords
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