Fukatsu Shoya, Sashi Hinami, Shirai Remina, Takagi Norio, Oizumi Hiroaki, Yamamoto Masahiro, Ohbuchi Katsuya, Miyamoto Yuki, Yamauchi Junji
Laboratory of Molecular Neurology, Tokyo University of Pharmacy and Life Sciences, Tokyo 192-0392, Japan.
Laboratory of Applied Biochemistry, Tokyo University of Pharmacy and Life Sciences, Tokyo 192-0392, Japan.
Pathophysiology. 2024 Feb 9;31(1):100-116. doi: 10.3390/pathophysiology31010008.
Abnormal nucleotide insertions of C9orf72, which forms a complex with Smith-Magenis syndrome chromosomal region candidate gene 8 (SMCR8) protein and WD repeat-containing protein 41 (WDR41) protein, are associated with an autosomal-dominant neurodegenerative frontotemporal dementia and/or amyotrophic lateral sclerosis type 1 (FTDALS1). The differentially expressed in normal and neoplastic cells (DENN) domain-containing C9orf72 and its complex with SMCR8 and WDR41 function as a guanine-nucleotide exchange factor for Rab GTP/GDP-binding proteins (Rab GEF, also called Rab activator). Among Rab proteins serving as major effectors, there exists Rab11a. However, it remains to be established which Rab protein is related to promoting or sustaining neuronal morphogenesis or homeostasis. In this study, we describe that the knockdown of Rab11a decreases the expression levels of neuronal differentiation marker proteins, as well as the elongation of neurite-like processes, using N1E-115 cells, a well-utilized neuronal differentiation model. Similar results were obtained in primary cortical neurons. In contrast, the knockdown of Rab11b, a Rab11a homolog, did not significantly affect their cell morphological changes. It is of note that treatment with hesperetin, a citrus flavonoid (also known as Vitamin P), recovered the neuronal morphological phenotypes induced by Rab11a knockdown. Also, the knockdown of Rab11a or Rab11b led to a decrease in glial marker expression levels and in morphological changes in FBD-102b cells, which serve as the oligodendroglial differentiation model. Rab11a is specifically involved in the regulation of neuronal morphological differentiation. The knockdown effect mimicking the loss of function of C9orf72 is reversed by treatment with hesperetin. These findings may reveal a clue for identifying one of the potential molecular and cellular phenotypes underlying FTDALS1.
C9orf72的异常核苷酸插入与常染色体显性神经退行性额颞叶痴呆和/或1型肌萎缩侧索硬化症（FTDALS1）相关，它与史密斯-马吉尼斯综合征染色体区域候选基因8（SMCR8）蛋白和含WD重复序列蛋白41（WDR41）蛋白形成复合物。含差异表达于正常细胞和肿瘤细胞（DENN）结构域的C9orf72及其与SMCR8和WDR41的复合物作为Rab GTP/GDP结合蛋白的鸟嘌呤核苷酸交换因子（Rab GEF，也称为Rab激活剂）发挥作用。在作为主要效应器的Rab蛋白中，存在Rab11a。然而，哪种Rab蛋白与促进或维持神经元形态发生或体内平衡相关仍有待确定。在本研究中，我们利用常用的神经元分化模型N1E-115细胞描述了，敲低Rab11a会降低神经元分化标志物蛋白的表达水平以及神经突样突起的伸长。在原代皮质神经元中也获得了类似结果。相比之下，敲低Rab11a的同源物Rab11b对其细胞形态变化没有显著影响。值得注意的是，用柑橘类黄酮橙皮素（也称为维生素P）处理可恢复由Rab11a敲低诱导的神经元形态表型。此外，敲低Rab11a或Rab11b会导致少突胶质细胞分化模型FBD-102b细胞中胶质细胞标志物表达水平降低和形态变化。Rab11a特别参与神经元形态分化的调节。橙皮素处理可逆转模拟C9orf72功能丧失的敲低效应。这些发现可能为确定FTDALS1潜在分子和细胞表型之一提供线索。
