美国斯坦福大学医学院Philip A. Beachy和加州大学程亦凡研究团队合作发现Dispatched 使用 Na+ 通量为脂质修饰的Hedgehog释放提供动力。相关论文于2021年10月27日发表在《自然》杂志上。

他们确定了小鼠蛋白质 Dispatched homologue 1 (DISP1) 的冷冻镜结构，揭示了三个 Na + 离子在穿过其跨膜结构域的通道内协调作用。他们发现 Hedgehog 输出的速率取决于跨质膜的 Na+ 梯度。DISP1-NNN 中的跨膜通道和 Na+ 结合被破坏，DISP1-NNN 是一种用天冬酰胺替代三个膜内天冬氨酸残基的变体，每个残基协调并中和三个 Na+ 离子之一的电荷。 DISP1-NNN 和破坏单个 Na+ 位点的变体保留与 SCUBE2 受体的结合，但在将脂质修饰的 Hedgehog 蛋白输出到 SCUBE2 受体时受到损害。声波刺猬蛋白 (ShhN) 的氨基末端信号结构域与 DISP1 的相互作用通过广泛的埋藏表面积和与扩展的弗林蛋白酶裂解 DISP1 臂的接触发生。

变异性分析表明，ShhN 结合仅限于一系列连续的 DISP1 构象中的一个极端。结合和未结合的 DISP1 构象显示出不同的 Na+ 位点占有率，这表明跨膜 Na+ 通量可以为从膜中提取脂质连接的 Hedgehog 信号提供动力的机制。 DISP1 中的 Na+ 配位残基在 PTCH1 和其他后生动物 RND 家族成员中是保守的，这表明 Na+ 通量为它们的构象驱动活动提供动力。

据介绍，Dispatched 蛋白与 NPC1 和 PTCH1 胆固醇转运蛋白以及 RND 家族的 H+ 驱动转运蛋白相关，通过从胚胎表达紧密定位的位点释放脂质修饰的 Hedgehog 蛋白，使其具有组织模式化活性。

附：英文原文

Title: Dispatched uses Na+ flux to power release of lipid-modified Hedgehog

Author: Wang, Qianqian, Asarnow, Daniel E., Ding, Ke, Mann, Randall K., Hatakeyama, Jason, Zhang, Yunxiao, Ma, Yong, Cheng, Yifan, Beachy, Philip A.

Issue&Volume: 2021-10-27

Abstract: The Dispatched protein, which is related to the NPC1 and PTCH1 cholesterol transporters1,2 and to H+-driven transporters of the RND family3,4, enables tissue-patterning activity of the lipid-modified Hedgehog protein by releasing it from tightly -localized sites of embryonic expression5,6,7,8,9,10. Here we determine a cryo-electron microscopy structure of the mouse protein Dispatched homologue 1 (DISP1), revealing three Na+ ions coordinated within a channel that traverses its transmembrane domain. We find that the rate of Hedgehog export is dependent on the Na+ gradient across the plasma membrane. The transmembrane channel and Na+ binding are disrupted in DISP1-NNN, a variant with asparagine substitutions for three intramembrane aspartate residues that each coordinate and neutralize the charge of one of the three Na+ ions. DISP1-NNN and variants that disrupt single Na+ sites retain binding to, but are impaired in export of the lipid-modified Hedgehog protein to the SCUBE2 acceptor. Interaction of the amino-terminal signalling domain of the Sonic hedgehog protein (ShhN) with DISP1 occurs via an extensive buried surface area and contacts with an extended furin-cleaved DISP1 arm. Variability analysis reveals that ShhN binding is restricted to one extreme of a continuous series of DISP1 conformations. The bound and unbound DISP1 conformations display distinct Na+-site occupancies, which suggests a mechanism by which transmembrane Na+ flux may power extraction of the lipid-linked Hedgehog signal from the membrane. Na+-coordinating residues in DISP1 are conserved in PTCH1 and other metazoan RND family members, suggesting that Na+ flux powers their conformationally driven activities.

DOI: 10.1038/s41586-021-03996-0

Source: https://www.nature.com/articles/s41586-021-03996-0