Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
J Cell Biol. 2013 Aug 5;202(3):495-508. doi: 10.1083/jcb.201302078. Epub 2013 Jul 29.
Regulation of the opposing kinesin and dynein motors that drive axonal transport is essential to maintain neuronal homeostasis. Here, we examine coordination of motor activity by the scaffolding protein JNK-interacting protein 1 (JIP1), which we find is required for long-range anterograde and retrograde amyloid precursor protein (APP) motility in axons. We identify novel interactions between JIP1 and kinesin heavy chain (KHC) that relieve KHC autoinhibition, activating motor function in single molecule assays. The direct binding of the dynactin subunit p150(Glued) to JIP1 competitively inhibits KHC activation in vitro and disrupts the transport of APP in neurons. Together, these experiments support a model whereby JIP1 coordinates APP transport by switching between anterograde and retrograde motile complexes. We find that mutations in the JNK-dependent phosphorylation site S421 in JIP1 alter both KHC activation in vitro and the directionality of APP transport in neurons. Thus phosphorylation of S421 of JIP1 serves as a molecular switch to regulate the direction of APP transport in neurons.
调节驱动轴突运输的相反的驱动蛋白和动力蛋白对于维持神经元内环境稳定至关重要。在这里，我们研究了支架蛋白 JNK 相互作用蛋白 1（JIP1）对运动活性的协调作用，我们发现它是轴突中长程顺行和逆行淀粉样前体蛋白（APP）运动所必需的。我们确定了 JIP1 和驱动蛋白重链（KHC）之间的新相互作用，这些相互作用可以解除 KHC 的自动抑制，在单分子测定中激活运动功能。动力蛋白复合物亚基 p150（Glued）与 JIP1 的直接结合在体外竞争性抑制 KHC 的激活，并破坏 APP 在神经元中的运输。这些实验共同支持了一个模型，即 JIP1 通过在顺行和逆行运动复合物之间切换来协调 APP 的运输。我们发现，JIP1 中 JNK 依赖性磷酸化位点 S421 的突变既改变了体外的 KHC 激活，也改变了神经元中 APP 运输的方向。因此，JIP1 的 S421 磷酸化作为一个分子开关，调节神经元中 APP 运输的方向。
