Bushlin Ittai, Petralia Ronald S, Wu Fangbai, Harel Asaff, Mughal Mohamed R, Mattson Mark P, Yao Pamela J
Laboratory of Neurosciences, National Institute on Aging-National Institutes of Health, Baltimore, Maryland 21224, USA.
J Neurosci. 2008 Oct 8;28(41):10257-71. doi: 10.1523/JNEUROSCI.2471-08.2008.
Emerging data suggest that, much like epithelial cells, the polarized growth of neurons requires both the secretory and endocytic pathways. The clathrin assembly proteins AP180 and CALM (clathrin assembly lymphoid myeloid protein) are known to be involved in clathrin-mediated endocytosis, but their roles in mammalian neurons and, in particular, in developmental processes before synaptogenesis are unknown. Here we provide evidence that AP180 and CALM play critical roles in establishing the polarity and controlling the growth of axons and dendrites in embryonic hippocampal neurons. Knockdown of AP180 primarily impairs axonal development, whereas reducing CALM levels results in dendritic dystrophy. Conversely, neurons that overexpress AP180 or CALM generate multiple axons. Ultrastructural analysis shows that CALM affiliates with a wider range of intracellular trafficking organelles than does AP180. Functional analysis shows that endocytosis is reduced in both AP180-deficient and CALM-deficient neurons. Additionally, CALM-deficient neurons show disrupted secretory transport. Our data demonstrate previously unknown functions for AP180 and CALM in intracellular trafficking that are essential in the growth of neurons.
新出现的数据表明，与上皮细胞非常相似，神经元的极性生长需要分泌途径和内吞途径。已知网格蛋白组装蛋白AP180和CALM（网格蛋白组装淋巴细胞髓样蛋白）参与网格蛋白介导的内吞作用，但它们在哺乳动物神经元中的作用，特别是在突触发生之前的发育过程中的作用尚不清楚。在这里，我们提供证据表明，AP180和CALM在建立胚胎海马神经元的极性以及控制轴突和树突的生长中起关键作用。敲低AP180主要损害轴突发育，而降低CALM水平则导致树突营养不良。相反，过表达AP180或CALM的神经元会产生多个轴突。超微结构分析表明，与AP180相比，CALM与更广泛的细胞内运输细胞器相关联。功能分析表明，AP180缺陷型和CALM缺陷型神经元的内吞作用均降低。此外，CALM缺陷型神经元显示出分泌运输中断。我们的数据证明了AP180和CALM在细胞内运输中以前未知的功能，这些功能在神经元生长中至关重要。
