Deactivation of phosphorylated and nonphosphorylated rhodopsin by arrestin splice variants
Deactivation of phosphorylated and nonphosphorylated rhodopsin by arrestin splice variants
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DOI：
10.1523/jneurosci.3301-05.2006
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发表时间：
2006-01-18
影响因子：
5.3
通讯作者：
Chen, J
中科院分区：
文献类型：
--
作者：
Burns, ME;Mendez, A;Chen, J
阻滞蛋白是介导g蛋白偶联受体（gpcr）失活的细胞质小蛋白家族，已知对级联失活和受体脱敏至关重要。选择性剪接产生一系列抑制蛋白基因产物，这些基因产物在体外对其同源受体具有广泛不同的特异性，但这些剪接变体在体内的差异功能基本上是未知的。牛杆状光感受器表达两种视阻蛋白剪接变体（p44和p48），它们对GPCR视紫红质表现出不同的亲和力。为了确定这些剪接变体在完整细胞中的功能，我们在缺乏内源性抑制蛋白（Arr(-/-)）的小鼠杆状细胞中表达了一种转基因，编码截断形式的小鼠抑制蛋白（mArr（1-369）或m44）或长（p48）亚型。形态学分析表明，任何一种变体的表达都减弱了被认为是由Arr（-/-）杆过度级联活性引起的光诱导变性。来自单个视杆的吸电极记录表明，m44或p48剪接变体的表达都可以恢复正常的Arr（-/-）微弱闪光反应动力学，这表明这两种异构体都可以快速结合并猝灭磷酸化的视紫红质。令我们惊讶的是，只有全长变异能够改变缺乏抑制蛋白和视紫红质激酶的视杆细胞的反应动力学，这表明p48也可以抑制非磷酸化视紫红质的活性。
Arrestins constitute a family of small cytoplasmic proteins that mediate deactivation of G-protein-coupled receptors (GPCRs) and are known to be essential for cascade inactivation and receptor desensitization. Alternative splicing produces an array of arrestin gene products that have widely different specificities for their cognate receptors in vitro, but the differential functions of these splice variants in vivo are essentially unknown. Bovine rod photoreceptors express two splice variants of visual arrestin (p44 and p48) that display different affinities for the GPCR rhodopsin. To determine the functions of these splice variants in intact cells, we expressed a transgene encoding either a truncated form of murine arrestin (mArr(1-369), or m44) or the long ( p48) isoform in mouse rods lacking endogenous arrestin (Arr(-/-)). Morphological analysis showed that expression of either variant attenuated the light-induced degeneration that is thought to result from excessive cascade activity in Arr(-/-) rods. Suction electrode recordings from individual rods indicated that the expression of either m44 or p48 splice variants could restore normal kinetics to Arr(-/-) dim flash responses, indicating that both isoforms can bind to and quench phosphorylated rhodopsin rapidly. To our surprise, only the full-length variant was able to alter the kinetics of responses in rods lacking both arrestin and rhodopsin kinase, indicating that p48 can also quench the activity of nonphosphorylated rhodopsin.