Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC H3A 2B4, Canada.
Department of Kinesiology and Physical Education, McGill University, Room 210, 475 Pine Avenue West, Montreal, QC H2W 1S4, Canada.
Int J Mol Sci. 2022 Dec 12;23(24):15742. doi: 10.3390/ijms232415742.
Autosomal Recessive Spastic Ataxia of the Charlevoix Saguenay (ARSACS) is caused by mutation in the SACS gene resulting in loss of function of the protein sacsin. A key feature is the formation of abnormal bundles of neurofilaments (NF) in neurons and vimentin intermediate filaments (IF) in cultured fibroblasts, suggesting a role of sacsin in IF homeostasis. Sacsin contains a J domain (SacsJ) homologous to Hsp40, that can interact with Hsp70 chaperones. The SacsJ domain resolved NF bundles in cultured neurons. Having studied the mechanism using NF assembled in vitro from purified NF proteins, we report that the SacsJ domain interacts with NF proteins to disassemble NFL filaments, and to inhibit their initial assembly. A cell-penetrating peptide derived from this domain, SacsJ-myc-TAT was efficient in disassembling NF bundles in cultured motor neurons, restoring the NF network; however, there was some loss of vimentin IF and NF in cultured fibroblasts and motor neurons, respectively. These results suggest that sacsin through its SacsJ domain is a key regulator of NF and vimentin IF networks in cells.
常染色体隐性痉挛性共济失调（ARCSACS）是由 SACS 基因突变引起的，导致蛋白 sacsin 功能丧失。一个关键特征是神经元中神经丝（NF）异常束的形成和培养成纤维细胞中的波形蛋白中间丝（IF），表明 sacsin 在 IF 动态平衡中起作用。Sacsin 含有与 Hsp40 同源的 J 结构域（SacsJ），可与 Hsp70 伴侣相互作用。SacsJ 结构域可在培养的神经元中解析 NF 束。使用从纯化的 NF 蛋白体外组装的 NF 研究其机制，我们报告 SacsJ 结构域与 NF 蛋白相互作用以解聚 NFL 纤维，并抑制其初始组装。来自该结构域的细胞穿透肽 SacsJ-myc-TAT 可有效分解培养的运动神经元中的 NF 束，恢复 NF 网络；然而，在培养的成纤维细胞和运动神经元中分别有一些波形蛋白 IF 和 NF 丢失。这些结果表明，通过其 SacsJ 结构域，sacsin 是细胞中 NF 和波形蛋白 IF 网络的关键调节剂。
