Wu Chunlai, Wairkar Yogesh P, Collins Catherine A, DiAntonio Aaron
Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Neurosci. 2005 Oct 19;25(42):9557-66. doi: 10.1523/JNEUROSCI.2532-05.2005.
Highwire is a huge, evolutionarily conserved protein that is required to restrain synaptic growth and promote synaptic transmission at the Drosophila neuromuscular junction. Current models of highwire function suggest that it may act as a ubiquitin ligase to regulate synaptic development. However, it is not known in which cells highwire functions, whether its putative ligase domain is required for function, or whether highwire regulates the synapse during development or alternatively sets cell fate in the embryo. We performed a series of transgenic rescue experiments to test the spatial, structural, and temporal requirements for highwire function. We find that presynaptic activity of highwire is both necessary and sufficient to regulate both synapse morphology and physiology. The Highwire RING domain, which is postulated to function as an E3 ubiquitin ligase, is required for highwire function. In addition, highwire acts throughout larval development to regulate synaptic morphology and function. Finally, we show that the morphological and physiological phenotypes of highwire mutants have different dosage and temporal requirements for highwire, demonstrating that highwire may independently regulate the molecular pathways controlling synaptic growth and function.
Highwire是一种巨大的、在进化上保守的蛋白质，在果蝇神经肌肉接头处，它对于抑制突触生长和促进突触传递是必需的。目前关于Highwire功能的模型表明，它可能作为一种泛素连接酶来调节突触发育。然而，尚不清楚Highwire在哪些细胞中发挥功能，其假定的连接酶结构域对于功能是否必需，或者Highwire是在发育过程中调节突触，还是在胚胎中决定细胞命运。我们进行了一系列转基因拯救实验，以测试Highwire功能在空间、结构和时间上的要求。我们发现，Highwire的突触前活性对于调节突触形态和生理功能既必要又充分。推测作为E3泛素连接酶发挥作用的Highwire RING结构域是Highwire功能所必需的。此外，Highwire在整个幼虫发育过程中都发挥作用，以调节突触形态和功能。最后，我们表明，Highwire突变体的形态和生理表型对Highwire有不同的剂量和时间要求，这表明Highwire可能独立调节控制突触生长和功能的分子途径。
