Apolipoprotein L-I is the trypanolytic factor of human serum. Here we show that this protein contains a membrane pore-forming domain functionally similar to that of bacterial colicins, flanked by a membrane-addressing domain. In lipid bilayer membranes, apolipoprotein L-I formed anion channels. In Trypanosoma brucei , apolipoprotein L-I was targeted to the lysosomal membrane and triggered depolarization of this membrane, continuous influx of chloride, and subsequent osmotic swelling of the lysosome until the trypanosome lysed.

An extra sugar protects: Many microbial pathogens produce proteins that are toxic to the cells that they are targeting. Broad-leaved plants are susceptible to NLP (necrosis and ethylene-inducing peptide 1–like protein) toxins. Lenarčič et al. identified the receptors for NLP toxins to be GIPC (glycosylinositol phosphorylceramide) sphingolipids (see the Perspective by Van den Ackerveken). Their findings reveal why these toxins only attack broad-leaved plants (so-called eudicots): If the sphingolipid carries just two hexoses, as is the case for eudicots, the toxin binds and causes cell lysis. But in monocots with sphingolipids that have three hexoses, the toxin is ineffective. Science , this issue p. 1431 ; see also p. 1383

Lipid composition of plasma membrane (PM) and the corresponding Detergent-Insoluble Membrane (DIM) fraction were analyzed with a specific focus on highly polar sphingolipids so-called Glycosyl-Inositol-Phosphoryl-Ceramides (GIPCs). Using tobacco Bright Yellow-2 cell suspension and tobacco leaves (Nicotiana tabacum), evidences were provided that GIPCs represent up to 40 mol% of the PM lipids. Comparative analysis of DIMs with the PM showed an enrichment of 2-hydroxylated Very Long Chain Fatty Acid (VLCFA)-containing GIPCs and polyglycosylated GIPCs in the DIMs. Purified antibodies raised against these GIPCs were further used for immunogold-electron microscopy strategy, revealing the distribution of polyglycosylated GIPCs in domains of 35{plus minus}7nm in the plane of the PM. Biophysical studies also showed strong interactions between GIPCs and sterols, and suggested a role for VLCFA in the interdigitation between the two PM composing-monolayers. The ins and outs of lipid asymmetry, raft formation and interdigitation in plant membrane biology are finally discussed.