Herding Potassium Channels

Kristen M. S. O'Connell, Annah S. Rolig, Jennifer D. Whitesell, and Michael M. Tamkun

Voltage-gated ion channels have to be in just the right spots for proper neuronal function. This week, O'Connell et al. examined the mechanisms governing localization of the delayed-rectifier channel Kv2.1. Previous work showed that these channels are clustered in the membrane of hippocampal neurons and transfected HEK (human embryonic kidney) cells. Using live imaging of cells expressing GFP (green fluorescent protein)-tagged Kv2.1, the authors found that individual channels within clusters were highly mobile. To watch the channels, they used FRAP (fluorescence recovery after photobleaching). To be sure that they were watching channels in the membrane, they also biotinylated channels and then tracked them using streptavidin-coated quantum dots. The high surface mobility appears inconsistent with tethering to scaffolding proteins. Instead, the clustering may involve the sequestration of mobile channels within what the authors call a "perimeter fence." New Kv2.1 channels were delivered to clusters by fusion of adjacent surface clusters and fusion of intracellular transport vesicles that contained channels.

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Herding Potassium Channels