Rab-GTPase-dependent endocytic recycling of KV1.5 in atrial myocytes
Rab-GTPase-dependent endocytic recycling of KV1.5 in atrial myocytes
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DOI：
10.1074/jbc.m704402200
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发表时间：
2007-10-05
影响因子：
4.8
通讯作者：
Martens, Jeffrey R.
中科院分区：
文献类型：
--
作者：
McEwen, Dyke P.;Schumacher, Sarah M.;Martens, Jeffrey R.
细胞表面表达的离子通道的数量决定了可兴奋细胞的复杂电反应。维持通道蛋白的顺行和逆行运输之间的平衡对于调节稳态细胞表面表达至关重要。Kv1.5是心血管系统中重要的电压门控性钾通道，是心房肌细胞中主要复极化电流超快速整流钾电流（Ik（ur））的基础，并调节平滑肌细胞的静息膜电位和兴奋性。Kv1.5表达缺陷与慢性房颤和缺氧性肺动脉高压等病理状态有关。因此，理解调节细胞表面通道水平的机制具有很大的兴趣。在这里，我们研究了Kv1.5在HL-1永生化小鼠心房肌细胞的内化和再循环。动力学研究表明，Kv1.5迅速内化到核周区域，在那里它与早期内体标记物EEA 1共定位。重要的是，我们确定了Kv1.5的群体，起源于细胞表面，内化并再循环回质膜。值得注意的是，Kv1.5再循环过程由特定的Rab依赖性内体隔室驱动。因此，GDP锁定Rab 4S 22 N和Rab 11 S25 N显性负突变体的共表达降低了稳态Kv1.5表面水平，而GTP酶缺陷型Rab 4 Q67 L和Rab 11 Q70 L突变体增加了稳态Kv1.5表面水平。这些数据揭示了一个意想不到的动态贩运Kv1.5在肌细胞质膜，并证明了在维持稳态离子通道表面水平回收的作用。
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 the ultra-rapid rectifying potassium current (Ik(ur)), a major repolarizing current in atrial myocytes, and regulating the resting membrane potential and excitability of smooth muscle cells. Defects in the 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 is rapidly internalized to a perinuclear region where it co-localizes 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.