Localization of Kv1.5 channels in rat and canine myocyte sarcolemma

Voltage-gated potassium (Kv) channel subtypes localize to the plasma membrane of a number of cell types, and the sarcolemma in myocytes. Because many signaling molecules concentrate in subdomains of the plasma membrane, the localization of Kv channels to these sites may have important implications for channel function and regulation. In this study, the association of the voltage-gated potassium channel Kv1.5 with a specific subtype of lipid rafts, caveolae, in rat and canine cardiac myocytes has been investigated. Interactions between caveolin-3 and beta-dystroglycan or eNOS, as well as between KvI.5 and alpha-actinin were readily detected in co-immunoprecipitation experiments, whereas no association between Kv1.5 and caveolin-3 was evident. Wide-field microscopy and deconvolution techniques revealed that the percent co-localization of KvI.5 with caveolin-3 was extremely low in atrial myocytes from rat and canine hearts (8 +/- 1% and 12.2 +/- 2%, respectively), and limited in ventricular myocytes (11 +/- 4% and 20 +/- 3% in rat and canine, respectively). Immunoelectron microscopic imaging of rat atrial and ventricular tissues showed that Kv1.5 and caveolin-3 labeling generally did not overlap. In REK293 cells stably expressing the channel, KvI.5 did not target to the low buoyant density raft fraction along with flo-tillin but instead fractionated along with the non-raft associated transferrin receptor. Taken together, these results suggest that Kv1.5 is not present in caveolae of rat and canine heart. (c) 2006 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.