Structure And Function Of Unconventional Myosins

内质网（ER）向浦肯野神经元（PNs）树突棘的延伸是小脑突触可塑性所必需的，并且在Myo5a（编码肌球蛋白- va1 -3的基因）零突变的动物中被破坏。虽然有人提出动物V类肌凝蛋白通过将细胞器拴在肌动蛋白细胞骨架上来定位细胞器4-7，但我们在这里证明了肌凝蛋白- va作为点对点的细胞器转运体将内质网作为货物拉入PN棘。具体来说，当细胞器进入脊柱时，肌凝蛋白在内质网尖端积累，并且肌凝蛋白水解ATP的能力是脊柱内质网靶向所必需的。此外，肌球蛋白- va是绝大多数脊柱内质网插入事件的原因。最后，肌凝蛋白沿肌动蛋白丝移动能力的衰减降低了内质网向脊柱移动的最大速度，这为肌凝蛋白- va驱动内质网运动提供了直接证据。因此，我们建立了一个基于肌动蛋白的马达在动物细胞内移动内质网，我们揭示了内质网定位到PN棘的机制，这是突触可塑性的先决条件。

Extension of the endoplasmic reticulum (ER) into dendritic spines of Purkinje neurons (PNs) is required for cerebellar synaptic plasticity and is disrupted in animals with null mutations in Myo5a, the gene encoding myosin-Va1-3. While it has been proposed that animal class V myosins localize organelles by tethering them to the actin cytoskeleton4-7, we demonstrate here that myosin-Va acts as a point-to-point organelle transporter to pull ER as cargo into PN spines. Specifically, the myosin accumulates at the ER tip as the organelle moves into spines, and the myosins ability to hydrolyze ATP is required for spine ER targeting. Moreover, myosin-Va is responsible for the vast majority of spine ER insertional events. Finally, attenuation of the myosins ability to move along actin filaments reduces the maximum velocity of ER movement into spines, providing direct evidence that myosin-Va drives ER motility. Thus, we establish that an actin-based motor moves ER within animal cells, and we uncover the mechanism that mediates ER localization to PN spines, a prerequisite for synaptic plasticity.