Supplementary Material for: Desmosterol in Brain Is Elevated because <b><i>DHCR24</i></b> Needs REST for Robust Expression but <b><i>REST</i></b> Is Poorly Expressed

Cholesterol synthesis in the fetal brain is inhibited because activity of DHCR24 (24-dehydrocholesterol reductase) is insufficient, causing concentrations of the precursor desmosterol to increase temporarily to 15-25% of total sterols at birth. We demonstrate that failure of <i>DHCR24</i> to be adequately upregulated during periods of elevated cholesterol synthesis in the brain results from the presence in its promoter of the repressor element 1 (RE1) nucleotide sequence that binds the RE1-silencing transcription factor (REST) and that REST, generally reduced in neural tissues, uncharacteristically but not without precedent, enhances <i>DHCR24</i> transcription. <i>DHCR24</i> and <i>REST</i> mRNA levels are reduced 3- to 4-fold in fetal mouse brain compared to liver (p < 0.001). Chromatin immunoprecipitation assays suggested that REST binds to the human <i>DHCR24</i> promoter in the vicinity of the predicted human RE1 sequence. Luminescent emission from a human <i>DHCR24</i> promoter construct with a mutated RE1 sequence was reduced 2-fold compared to output from a reporter with wild-type RE1 (p < 0.005). Silencing <i>REST</i> in HeLa cells resulted in significant reductions of <i>DHCR24</i> mRNA (2-fold) and DHCR24 protein (4-fold). As expected, relative concentrations of Δ²⁴-cholesterol precursor sterols increased 3- to 4-fold, reflecting the inhibition of DHCR24 enzyme activity. In contrast, mRNA levels of <i>DHCR7</i> (sterol 7-dehydrocholesterol reductase), a gene essential for cholesterol synthesis lacking an RE1 sequence, and concentrations of HMGR (3-hydroxy-3-methyl-glutaryl-CoA reductase) enzyme protein were both unaffected. Surprisingly, a dominant negative fragment of REST consisting of just the DNA binding domain (about 20% of the protein) and full-length REST enhanced <i>DHCR24</i> expression equally well. Furthermore, RE1 and the sterol response element (SRE), the respective binding sites for REST and the SRE binding protein (SREBP), are contiguous. These observations led us to hypothesize that REST acts because it is bound in close proximity to SREBP, thus amplifying its ability to upregulate <i>DHCR24</i>. It is likely that modulation of <i>DHCR24</i> expression by REST persisted in the mammalian genome either because it does no harm or because suppressing metabolically active DHCR24 while providing abundant quantities of the multifunctional sterol desmosterol during neural development proved useful

Supplementary Material for: Perilipin1 deficiency prompts lipolysis in lipid droplets and aggravates the pathogenesis of persistent immune activation in Drosophila

Lipid droplets (LDs) are highly dynamic intracellular organelles, which are involved in lots of biological processes. However, the dynamic morphogenesis and functions of intracellular LDs during persistent innate immune responses remain obscure. In this study, we induce long-term systemic immune activation in Drosophila through genetic manipulation. Then, the dynamic pattern of LDs is traced in the Drosophila fat body. We find that deficiency of Plin1, a key regulator of LDs’ reconfiguration, blocks LDs minimization at the initial stage of immune hyperactivation but enhances LDs breakdown at the later stage of sustained immune activation via recruiting the lipase Brummer (Bmm, homologous to human ATGL). The high wasting in LDs shortens the lifespan of flies with high-energy-cost immune hyperactivation. Therefore, these results suggest a critical function of LDs during long-term immune activation and provide a potential treatment for the resolution of persistent inflammation

Supplementary Material for: Perilipin1 deficiency prompts lipolysis in lipid droplets and aggravates the pathogenesis of persistent immune activation in Drosophila

Lipid droplets (LDs) are highly dynamic intracellular organelles, which are involved in lots of biological processes. However, the dynamic morphogenesis and functions of intracellular LDs during persistent innate immune responses remain obscure. In this study, we induce long-term systemic immune activation in Drosophila through genetic manipulation. Then, the dynamic pattern of LDs is traced in the Drosophila fat body. We find that deficiency of Plin1, a key regulator of LDs’ reconfiguration, blocks LDs minimization at the initial stage of immune hyperactivation but enhances LDs breakdown at the later stage of sustained immune activation via recruiting the lipase Brummer (Bmm, homologous to human ATGL). The high wasting in LDs shortens the lifespan of flies with high-energy-cost immune hyperactivation. Therefore, these results suggest a critical function of LDs during long-term immune activation and provide a potential treatment for the resolution of persistent inflammation