Kapiloff M S, Schillace R V, Westphal A M, Scott J D
Howard Hughes Medical Institute, L-474, Vollum Institute, Portland OR 97201-3098, USA.
J Cell Sci. 1999 Aug;112 ( Pt 16):2725-36. doi: 10.1242/jcs.112.16.2725.
The compartmentalization of second messenger-activated protein kinases contributes to the fidelity of hormone-mediated signal transduction events. For example, the cAMP-dependent protein kinase is tethered at specific intracellular locations through association with A-kinase anchoring proteins (AKAPs). We now report the cloning of mAKAP, an anchoring protein found predominantly in heart, skeletal muscle and brain, and whose expression is induced in neonatal ventriculocytes by treatment with hypertrophic stimuli. mAKAP is targeted to the nuclear membrane of differentiated myocytes. Analysis of mAKAP-green fluorescent protein (GFP) fusion constructs revealed that nuclear membrane targeting is conferred by two regions of the protein, between residues 772-915 and 915-1065, which contain spectrin-like repeat sequences. Heterologous expression of the mAKAP targeting sequences displaced the endogenous anchoring protein from the nuclear membrane, demonstrating that mAKAP targeting is saturable. Collectively, these data suggest that a domain containing spectrin-like repeats mediates targeting of the anchoring protein mAKAP and the cAMP-dependent protein kinase holoenzyme to the nuclear membrane in response to differentiation signals.
第二信使激活的蛋白激酶的区室化有助于激素介导的信号转导事件的保真度。例如，环磷酸腺苷（cAMP）依赖性蛋白激酶通过与A激酶锚定蛋白（AKAPs）结合而锚定在特定的细胞内位置。我们现在报告了mAKAP的克隆，mAKAP是一种主要在心脏、骨骼肌和大脑中发现的锚定蛋白，其表达在新生心室细胞中通过肥大刺激处理而被诱导。mAKAP定位于分化心肌细胞的核膜。对mAKAP-绿色荧光蛋白（GFP）融合构建体的分析表明，核膜靶向由该蛋白的两个区域赋予，位于残基772 - 915和915 - 1065之间，这两个区域包含血影蛋白样重复序列。mAKAP靶向序列的异源表达将内源性锚定蛋白从核膜上置换下来，表明mAKAP靶向是可饱和的。总体而言，这些数据表明，一个包含血影蛋白样重复序列的结构域介导了锚定蛋白mAKAP和cAMP依赖性蛋白激酶全酶响应分化信号而靶向核膜。
