Conserved function of ether lipids and sphingolipids in the early secretory pathway

Abstract

Sphingolipids have been shown to play important roles in physiology and cell biology, but a systematic examination of their functions is lacking. We performed a genome-wide CRISPRi screen in sphingolipid-depleted cells and identified hypersensitive mutants in genes of membrane trafficking and lipid biosynthesis, including ether lipid synthesis. Systematic lipidomic analysis showed a coordinate regulation of ether lipids with sphingolipids, where depletion of one of these lipid types resulted in increases in the other, suggesting an adaptation and functional compensation. Biophysical experiments on model membranes show common properties of these structurally diverse lipids that also share a known function as GPI anchors in different kingdoms of life. Molecular dynamics simulations show a selective enrichment of ether phosphatidylcholine around p24 proteins, which are receptors for the export of GPI-anchored proteins and have been shown to bind a specific sphingomyelin species. Our results support a model of convergent evolution of proteins and lipids, based on their physico-chemical properties, to regulate GPI-anchored protein transport and maintain homeostasis in the early secretory pathway.

Ultrastructure of COPII vesicle formation characterised by correlative light and electron microscopy

“…Sar1 may locally reduce the bending modulus of the lipid bilayer and facilitate spontaneous positive curvature (Hanna et al, 2016; Lee et al, 2005; Loftus et al, 2012; Settles et al, 2010) thus counter-balancing the growing repulsive forces within the ER lumen as the coat polymerizes (Copic et al, 2012). Moreover, the lipid environment may be locally remodelled with lipid species that facilitate membrane bending or stabilize cargo within the unfavourable conditions of vesicle lumen (Jiménez-Rojo et al, 2019; Melero et al, 2018; Rodriguez-Gallardo et al, 2020). Recruitment of Sec13/Sec31 rods would promote the ordered arrangement of the inner coat (Hutchings et al, 2021; Ma and Goldberg, 2016), thus reducing the bud radius (Gomez-Navarro et al, 2020).…”

Ultrastructure of COPII vesicle formation in yeast characterized by correlative light and electron microscopy

“…Moreover, the lipid environment may be locally remodeled with lipid species that facilitate membrane bending or stabilize cargo under the unfavorable conditions of the vesicle lumen ( Melero et al. , 2018 ; Jiménez-Rojo et al. , 2019 ; Rodriguez-Gallardo et al.…”

A highly efficient gene disruption strategy reveals lipid co-regulatory networks

“…Due to the importance of the co-regulation between SLs and ether PC to maintain the integrity of the secretory pathway [12], we further analyzed the mechanisms of ether lipid changes in CERS2 mutants.…”

“…This co-regulation leads to membrane lipid compositions that modulate immune responses upon various stimuli [11]. In addition, we recently found that sphingolipids (SLs) and ether phosphatidylcholine (ether PC) are co-regulated, which is critical to maintain the integrity of the secretory pathway [12]. While these studies establish the importance of lipid co-regulation, the mechanisms linking the quantitative change of one lipid to that of another one remains poorly understood.…”

“…Experiments performed on different days are distinguished by colors. (H) Design of the sgRNA against HPRT1 (sgRNA with a full match, fm) or its 14 variants (mm[1][2][3][4][5][6][7][8][9][10][11][12][13][14] with mismatches (in red) used to establish GENF in HeLa MZ cells. The sgRNAs that enabled the generation of 6-TG resistant cells are labeled with a tick and the others with a cross.…”