Homeostatic regulation of Kv1.2 potassium channel trafficking by cyclic AMP.
The Shaker family potassium channel, Kv1.2, is a key determinant of membrane excitability in neurons and cardiovascular tissue. Kv1.2 is subject to multiple forms of regulation and therefore integrates cellular signals involved in the homeostasis of excitability. The cyclic AMP/protein kinase A (PKA) pathway enhances Kv1.2 ionic current; however, the mechanisms for this are not fully known. Here we show that cAMP maintains Kv1.2 homeostasis through opposing effects on channel trafficking. We found that Kv1.2 is regulated by two distinct cAMP pathways, one PKA-dependent and the other PKA-independent. PKA inhibitors elevate Kv1.2 surface levels, suggesting that basal levels of cAMP control steady-state turnover of the channel. Elevation of cAMP above basal levels also increases the amount of Kv1.2 at the cell surface. This effect is not blocked by PKA inhibitors, but is blocked by inhibition of Kv1.2 endocytosis. We conclude that Kv1.2 levels at the cell surface are kept in dynamic balance by opposing effects of cAMP.
Connors
Emilee C
EC
Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont 05405.
Ballif
Bryan A
BA
Department of Biology, University of Vermont, Burlington, Vermont 05405.
Morielli
Anthony D
AD
Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont 05405. Electronic address: anthony.morielli@uvm.edu.
D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D004705:Endocytosis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006706:Homeostasis; D006801:Humans; D007477:Ions; D051663:Kv1.2 Potassium Channel / Q000378:metabolism*; D013058:Mass Spectrometry / Q000379:methods; D008954:Models, Biological; D010766:Phosphorylation; D012694:Serine / Q000737:chemistry
D004791:Enzyme Inhibitors; D007477:Ions; D051663:Kv1.2 Potassium Channel; D012694:Serine; D000242:Cyclic AMP