Vps13-like proteins provide phosphatidylethanolamine for GPI anchor synthesis in the ER

Glycosylphosphatidylinositol (GPI) is a glycolipid membrane anchor found on surface proteins in all eukaryotes. It is synthesized in the ER membrane. Each GPI anchor requires three molecules of ethanolamine phosphate (P-Etn), which are derived from phosphatidylethanolamine (PE). We found that efficient GPI anchor synthesis in Saccharomyces cerevisiae requires Csf1; cells lacking Csf1 accumulate GPI precursors lacking P-Etn. Structure predictions suggest Csf1 is a tube-forming lipid transport protein like Vps13. Csf1 is found at contact sites between the ER and other organelles. It interacts with the ER protein Mcd4, an enzyme that adds P-Etn to nascent GPI anchors, suggesting Csf1 channels PE to Mcd4 in the ER at contact sites to support GPI anchor biosynthesis. CSF1 has orthologues in Caenorhabditis elegans (lpd-3) and humans (KIAA1109/TWEEK); mutations in KIAA1109 cause the autosomal recessive neurodevelopmental disorder Alkuraya-Kučinskas syndrome. Knockout of lpd-3 and knockdown of KIAA1109 reduced GPI-anchored proteins on the surface of cells, suggesting Csf1 orthologues in human cells support GPI anchor biosynthesis.

MicroRNA Expression Profile Analysis of Chlamydomonas reinhardtii during Lipid Accumulation Process under Nitrogen Deprivation Stresses

Lipid accumulation in various microalgae has been found induced by nitrogen deprivation, and it controls many different genes expression. Yet, the underlying molecular mechanisms still remain largely unknown. MicroRNA (miRNAs) play a critical role in post-transcriptional gene regulation. In this study, miRNAs were hypothesized involved in lipid accumulation by nitrogen deprivation. A deep-sequencing platform was used to explore miRNAs-mediated responses induced by nitrogen deprivation in Chlamydomonas reinhardtii. The eukaryotic orthologous groups of proteins (KOG) function in the predicted target genes of miRNA with response to nitrogen deprivation were mainly involved in signal transduction mechanisms, including transcription, lipid transport, and metabolism. A total of 109 miRNA were predicted, including 79 known miRNA and 30 novel miRNA. A total of 29 miRNAs showed significantly differential expressions after nitrogen deprivation, and most of them were upregulated. A total of 10 miRNAs and their targeting genes might involve in lipid transport and metabolism biological process. This study first investigates nitrogen deprivation-regulated miRNAs in microalgae and broadens perspectives on miRNAs importance in microalgae lipid accumulation via nitrogen deprivation. This study provides theoretical guidance for the application of microalgae in bio-oil engineering production.

Colonization of mutualistic mycorrhizal and parasitic blast fungi requires OsRAM2-regulated fatty acid biosynthesis in rice

Arbuscular mycorrhizal (AM) fungi form a mutual association with the majority of land plants, including most angiosperms of the dicotyledon and monocotyledon lineages. The symbiosis is based upon bidirectional nutrient exchange between the host and symbiont that occurs between inner cortical cells of the root and branched AM hyphae called arbuscules that develop within these cells. Lipid transport and its regulation during the symbiosis have been intensively investigated in dicotyledon plants, especially legumes. Here, we characterize OsRAM2 and OsRAM2L, homologs of M. truncatula RAM2, and found that plants defective in OsRAM2 were unable to be colonized by AM fungi and showed impaired colonization by Magnaporthe oryzae. The induction of OsRAM2 and OsRAM2L is dependent on OsRAM1 and the CSSP pathway genes CCaMK and CYCLOPS, while overexpression of OsRAM1 results in increased expression of OsRAM2 and OsRAM2L. Collectively, our data show that the function and regulation of OsRAM2 is conserved in monocot and dicot plants and reveals that, similar to mutualistic fungi, pathogenic fungi have recruited RAM2-mediated fatty acid biosynthesis to facilitate invasion.

Energetics of lipid transport by the ABC transporter MsbA is lipid dependent

The ABC multidrug exporter MsbA mediates the translocation of lipopolysaccharides and phospholipids across the plasma membrane in Gram-negative bacteria. Although MsbA is structurally well characterised, the energetic requirements of lipid transport remain unknown. Here, we report that, similar to the transport of small-molecule antibiotics and cytotoxic agents, the flopping of physiologically relevant long-acyl-chain 1,2-dioleoyl (C18)-phosphatidylethanolamine in proteoliposomes requires the simultaneous input of ATP binding and hydrolysis and the chemical proton gradient as sources of metabolic energy. In contrast, the flopping of the large hexa-acylated (C12-C14) Lipid-A anchor of lipopolysaccharides is only ATP dependent. This study demonstrates that the energetics of lipid transport by MsbA is lipid dependent. As our mutational analyses indicate lipid and drug transport via the central binding chamber in MsbA, the lipid availability in the membrane can affect the drug transport activity and vice versa.

Disorders of lipid metabolism and lipid transport system in women with unstable angina in the dependence on smoking: pathogenetic connections and development risks

The aim of the study. To study the effect of smoking on lipid metabolism, lipid transport system and systemic inflammation, to find out their correlations and the risks of unstable angina in women, depending on the habit of smoking.Material and methods. 225 women were examined: 150 women - patients with unstable angina and 75 healthy women. The level of total cholesterol, low and high-density lipoprotein cholesterol, triglycerides, apolipoproteins A1 (ApoA1) and B (ApoB), C-reactive protein, fibrinogen were determined in all subjects. Multifactor correlation-regression analysis was performed using Fisher's test. Statistical processing of the results was performed using the applications "Microsoft Office Excel 2016" and "Statistics ver. 10.Results. The relative risk of developing unstable angina in patients with a smoking habit is most often associated with atherogenic dyslipidemia (total cholesterol > 4 mmol, OR = 12.02, SI = 8.12-16.32; low-density lipoprotein cholesterol > 1.8 mmol / l, OR = 9,32, SI = 6,13-12,56, high-density lipoprotein cholesterol <1,2 mmol / l, OR = 3,91, SI = 2,12-5,45, the ratio of apolipoproteins ApoV / ApoA1> 0.85, OR = 2.69, SI = 1.15-4.21) and the highest activity of systemic inflammation (C-reactive protein >3 mg / l, OR = 3.62, SI = 2.15- 4.56). The risk of developing unstable angina associated with these indicators is 1.5-2 times higher in women with a smoking habit than in women who have never smoked. Significant direct correlations of high and medium strength between the severity of systemic inflammation, disorders of the lipid transport system (increase in the ratio of ApoB / ApoA1 and decrease in the level of ApoA1), in patients with unstable angina in women smokers.Conclusions. Smoking is one of the most aggressive factors of unstable angina in women, which contributes to the emergence and progression of other important risk factors and leads to disorders of lipid metabolism, lipid transport system, systemic inflammation and increased chances of unstable angina.