School of Biotechnology, Jawaharlal Nehru University, New Delhi 110067, India.
CSIR Institute of Genomics and Integrative Biology, New Delhi 110025, India.
Int J Biochem Cell Biol. 2022 Aug;149:106258. doi: 10.1016/j.biocel.2022.106258. Epub 2022 Jun 28.
Limited treatment options and research in understanding the pathomechanisms of rare diseases has raised concerns about their therapeutic development. One such poorly understood ultra-rare neuromuscular disorder is GNE Myopathy (GNEM) which is caused due to mutation in key sialic acid biosynthetic enzyme, GNE. Treatment with sialic acid or its derivatives/precursors slows the disease progression, but curative strategies need to be explored further. Pathologically, muscle biopsy samples of GNEM patients reveal rimmed vacuole formation due to aggregation of β-amyloid, Tau, presenilin proteins with unknown mechanism. The present study aims to understand the mechanism of protein aggregate formation in GNE mutant cells to decipher role of chaperones in disease phenotype. The pathologically relevant GNE mutations expressed as recombinant proteins in HEK cells was used as a model system for GNEM to estimate extent of protein aggregation. We identified HSP70, a chaperone, as binding partner of GNE. Downregulation of HSP70 with altered BAG3, JNK, BAX expression levels was observed in GNE mutant cells. The cell apoptosis was observed in GNE mutation specific manner. An activator of HSP70 chaperone, BGP-15, rescued the phenotypic defects due to GNE mutation, thereby, reducing protein aggregation significantly. The results were further validated in rat skeletal muscle cell lines carrying single Gne allele. Our study suggests that HSP70 activators can be a promising therapeutic target in the treatment of ultra-rare GNE Myopathy disease.
治疗选择有限，对罕见病发病机制的研究也不足，这引发了人们对其治疗方法开发的担忧。有一种了解甚少的超罕见神经肌肉疾病是 GNE 肌病（GNEM），它是由关键唾液酸生物合成酶 GNE 的突变引起的。使用唾液酸或其衍生物/前体进行治疗可以减缓疾病进展，但需要进一步探索更有效的治疗策略。GNEM 患者的肌肉活检样本显示，由于β-淀粉样蛋白、Tau、早老素蛋白的聚集形成了边缘空泡，病理上存在 rimmed vacuole formation。目前的研究旨在了解 GNE 突变细胞中蛋白聚集体形成的机制，以阐明伴侣蛋白在疾病表型中的作用。该研究使用在 HEK 细胞中表达的具有病理相关性的 GNE 突变重组蛋白作为 GNEM 的模型系统，以评估蛋白聚集的程度。研究发现 HSP70 是一种伴侣蛋白，与 GNE 结合。在 GNE 突变细胞中观察到 HSP70 的下调，同时伴随着 BAG3、JNK、BAX 表达水平的改变。观察到 GNE 突变特异性的细胞凋亡。HSP70 伴侣蛋白的激活剂 BGP-15 可挽救由于 GNE 突变引起的表型缺陷，从而显著减少蛋白聚集。在携带单个 Gne 等位基因的大鼠骨骼肌细胞系中进一步验证了这些结果。本研究表明，HSP70 激活剂可能成为治疗超罕见 GNE 肌病的有前途的治疗靶点。
