Akum Barbara F, Chen Maxine, Gunderson Samuel I, Riefler Gary M, Scerri-Hansen Monica M, Firestein Bonnie L
Department of Cell Biology and Neuroscience, and Molecular Biosciences Graduate Program, Rutgers University, 604 Allison Road, Piscataway, New Jersey 08854-8082, USA.
Nat Neurosci. 2004 Feb;7(2):145-52. doi: 10.1038/nn1179. Epub 2004 Jan 18.
Dendrite branching has an important role in normal brain function. Here we report that overexpression of cypin, a protein that has guanine deaminase activity and is expressed in developing processes in rat hippocampal neurons, results in increased dendrite branching in primary culture. Mutant cypin proteins that lack guanine deaminase activity act in a dominant-negative manner when expressed in primary neurons. Furthermore, we knocked down cypin protein levels using a new strategy: expressing a 5' end-mutated U1 small nuclear RNA (snRNA) to inhibit maturation of cypin mRNA. Neurons that express this mutant snRNA show little or no detectable cypin protein and fewer dendrites than normal. In addition, we found that cypin binds directly to tubulin heterodimers and promotes microtubule polymerization. Thus, our results demonstrate a new pathway by which dendrite patterning is regulated, and we also introduce a new method for decreasing endogenous protein expression in neurons.
树突分支在正常脑功能中起着重要作用。在此我们报告，cypin（一种具有鸟嘌呤脱氨酶活性且在大鼠海马神经元发育过程中表达的蛋白质）的过表达导致原代培养中树突分支增加。缺乏鸟嘌呤脱氨酶活性的突变型cypin蛋白在原代神经元中表达时以显性负性方式起作用。此外，我们使用一种新策略降低cypin蛋白水平：表达5'端突变的U1小核RNA（snRNA）以抑制cypin mRNA的成熟。表达这种突变型snRNA的神经元显示出很少或几乎检测不到的cypin蛋白，并且树突比正常情况少。此外，我们发现cypin直接与微管蛋白异二聚体结合并促进微管聚合。因此，我们的结果证明了一种调节树突模式的新途径，并且我们还引入了一种降低神经元内源性蛋白质表达的新方法。
