An essential role for constitutive endocytosis, but not activity, in the axonal targeting of the CB1 cannabinoid receptor
An essential role for constitutive endocytosis, but not activity, in the axonal targeting of the CB1 cannabinoid receptor
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DOI：
10.1124/mol.106.029348
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发表时间：
2007-04-01
影响因子：
3.6
通讯作者：
Irving, Andrew J.
中科院分区：
文献类型：
--
作者：
McDonald, Neil A.;Henstridge, Christopher M.;Irving, Andrew J.
在中枢神经元中，大麻素受体亚型-1（CB 1）的细胞表面分布高度极化朝向轴突，并与突触末梢相关，在突触末梢中，它被很好地定位以调节神经递质的释放。已经表明，高水平的组成型活性介导CB 1受体轴突靶向，导致结构域特异性内吞作用。我们进一步研究了海马神经元CB 1受体轴突极化的机制，发现组成性活动不是这一过程的基本要求。我们证明，细胞表面分布的N-末端标记的荧光CB 1受体融合蛋白几乎完全定位于轴突时，在培养的海马神经元中表达。通过与显性负性发动蛋白-1（K44 A）突变体共转染抑制胞吞作用，将重组和内源性CB 1受体困在体树突状细胞表面。然而，这种效果不能通过抑制组成型活性或受体活化来模拟，无论是通过表达缺乏这些特性的突变体受体，还是通过用具有反向激动剂活性的CB 1受体拮抗剂治疗。这些数据是一致的修订模型，其中域特异性内吞调节CB 1受体的功能极化，但这个过程是不同的组成活动。
In central neurons, the cell-surface distribution of cannabinoid receptor subtype-1 (CB1) is highly polarized toward axons and is associated with synaptic terminals, in which it is well-positioned to modulate neurotransmitter release. It has been suggested that high levels of constitutive activity mediate CB1 receptor axonal targeting, leading to domain-specific endocytosis. We have investigated further the mechanisms that underlie CB1 receptor axonal polarization in hippocampal neurons and found that constitutive activity is not an essential requirement for this process. We demonstrate that the cell-surface distribution of an N-terminally tagged, fluorescent CB1 receptor fusion-protein is almost exclusively localized to the axon when expressed in cultured hippocampal neurons. Inhibition of endocytosis by cotransfection with a dominant-negative dynamin-1 (K44A) mutant traps both recombinant and endogenous CB1 receptors at the somatodendritic cell surface. However, this effect could not be mimicked by inhibiting constitutive activity or receptor activation, either by expressing mutant receptors that lack these properties or by treatment with CB1 receptor antagonists possessing inverse agonist activity. These data are consistent with a revised model in which domain-specific endocytosis regulates the functional polarization of CB1 receptors, but this process is distinct from constitutive activity.