The effect of eIF2B mutation on Cholesterol metabolism

Cholesterol, the major sterol in mammalian cells, is vital for normal cellular function and is especially abundant in myelin. Cholesterol biosynthesis is a highly energy-demanding process, tightly regulated at multiple levels including transcription, alternative splicing, post-translation modifications, and protein degradation. Regulatory mechanisms at the level of mRNA translation are less clear. Translation initiation factor 2B (eIF2B) is a master regulator of global translation, at the center of the Integrated Stress Response (ISR). Mutations in subunits of eIF2B lead to Vanishing White Matter (VWM), a genetic neurodegenerative disease characterized by loss of myelin in the CNS. Previous work in the lab using primary astrocytes isolated from eIF2B5R132H/R132H mice revealed abnormal expression levels of genes involved in cholesterol metabolism compared to WT primary astrocytes, leading to the hypothesis that cholesterol metabolism is also regulated at the translation level. In this study, we assessed the effect of 25-hydroxycholesterol (25-HC) on expression level of genes involved in cholesterol biosynthesis and export in astrocytes isolated from brains of eIF2B5R132H/R132H and WT mice. Differences were observed in the protein levels of APOE, ABCA1 and SREBP-2. We also found slight differences in translation rates mediated by the 5’UTRs of APOE and ABCA1 mRNAs. This study provides primary evidence that cholesterol metabolism is also regulated at the level of mRNA translation, and that this regulation is important for proper function of the CNS.