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Papers In Press, published online ahead of print August 2, 2007
Pharmacology, University of Michigan, Ann Arbor, MI 48109
Corresponding Author: martensj{at}umich.edu
The number of ion channels expressed on the cell surface shapes the complex electrical response of excitable cells. Maintaining a balance between anterograde and retrograde trafficking of channel proteins is vital in regulating steady-state cell surface expression. Kv1.5 is an important voltage-gated K+ channel in the cardiovascular system underlying Ikur, a major repolarizing current in atrial myocytes, and regulating the resting membrane potential and excitability of smooth muscle cells. Defects in expression of Kv1.5 are associated with pathological states such as chronic atrial fibrillation and hypoxic pulmonary hypertension. There is, thus, substantial interest in understanding the mechanisms regulating cell surface channel levels. Here, we investigated the internalization and recycling of Kv1.5 in the HL-1 immortalized mouse atrial myocytes. Kinetic studies indicate that Kv1.5 was rapidly internalized to a perinuclear region where it co-localized with the early endosomal marker, EEA1. Importantly, we identified that a population of Kv1.5, originating on the cell surface, internalized and recycled back to the plasma membrane. Notably, Kv1.5 recycling processes are driven by specific Rab-dependent endosomal compartments. Thus, co-expression of GDP-locked Rab4S22N and Rab11S25N dominant-negative mutants decreased the steady-state Kv1.5 surface levels, whereas GTPase-deficient Rab4Q67L and Rab11Q70L mutants increased steady-state Kv1.5 surface levels. These data reveal an unexpected dynamic trafficking of Kv1.5 at the myocyte plasma membrane and demonstrate a role for recycling in the maintenance of steady-state ion channel surface levels.
J. Biol. Chem, 10.1074/jbc.M704402200
Submitted on May 29, 2007
Revised on July 31, 2007
Accepted on August 2, 2007
RAB-GTPase dependent endocytic recycling of Kv1.5 in atrial myocytes
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