Structures of Lysenin Reveal a Shared Evolutionary Origin for Pore-Forming Proteins And Its Mode of Sphingomyelin Recognition
ABSTRACT Pore-forming proteins insert from solution into membranes to create lesions, undergoing a structural rearrangement often accompanied by oligomerization. Lysenin, a pore-forming toxin from the earthworm Eisenia fetida, specifically interacts with sphingomyelin (SM) and may confer innate immunity against parasites by attacking their membranes to form pores. SM has important roles in cell membranes and lysenin is a popular SM-labeling reagent. The structure of lysenin suggests common ancestry with other pore-forming proteins from a diverse set of eukaryotes and prokaryotes. The complex with SM shows the mode of its recognition by a protein in which both the phosphocholine headgroup and one acyl tail are specifically bound. Lipid interaction studies and assays using viable target cells confirm the functional reliance of lysenin on this form of SM recognition.
SourceAvailable from: Björn Marcus Von Reumont[Show abstract] [Hide abstract]
ABSTRACT: Glycerids are marine annelids commonly known as bloodworms. Bloodworms have an eversible proboscis adorned with jaws connected to venom glands. Bloodworms prey on invertebrates, and it is known that the venom glands produce compounds that can induce toxic effects in animals. Yet, none of these putative toxins have been characterized on a molecular basis. Here we present the transcriptomic profiles of the venom glands of three species of bloodworm, Glycera dibranchiata, G. fallax and G. tridactyla, as well as the body tissue of G. tridactyla. The venom glands express a complex mixture of transcripts coding for putative toxin precursors. These transcripts represent 20 known toxin classes that have been convergently recruited into animal venoms, as well as transcripts potentially coding for Glycera-specific toxins. The toxins represent five functional categories: pore-forming and membrane-disrupting toxins, neurotoxins, protease inhibitors, other enzymes, and CAP domain toxins. Many of the transcripts coding for putative Glycera toxins belong to classes that have been widely recruited into venoms, but some are homologs of toxins previously only known from the venoms of scorpaeniform fish and monotremes (stonustoxin-like toxin), turrid gastropods (turripeptide-like peptides), and sea anemones (gigantoxin I-like neurotoxin). This complex mixture of toxin homologs suggests that bloodworms employ venom while predating on macroscopic prey, casting doubt on the previously widespread opinion that G. dibranchiata is a detritivore. Our results further show that researchers should be aware that different assembly methods, as well as different methods of homology prediction, can influence the transcriptomic profiling of venom glands.Genome Biology and Evolution 09/2014; 6(9). DOI:10.1093/gbe/evu190 · 4.53 Impact Factor
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ABSTRACT: Sphingomyelin (SM) is a major sphingolipid in mammalian cells and is reported to form specific lipid domains together with cholesterol. However, methods to examine the membrane distribution of SM are limited. We demonstrated in model membranes that fluorescent protein conjugates of 2 specific SM-binding toxins, lysenin (Lys) and equinatoxin II (EqtII), recognize different membrane distributions of SM; Lys exclusively binds clustered SM, whereas EqtII preferentially binds dispersed SM. Freeze-fracture immunoelectron microscopy showed that clustered but not dispersed SM formed lipid domains on the cell surface. Glycolipids and the membrane concentration of SM affect the SM distribution pattern on the plasma membrane. Using derivatives of Lys and EqtII as SM distribution-sensitive probes, we revealed the exclusive accumulation of SM clusters in the midbody at the time of cytokinesis. Interestingly, apical membranes of differentiated epithelial cells exhibited dispersed SM distribution, whereas SM was clustered in basolateral membranes. Clustered but not dispersed SM was absent from the cell surface of acid sphingomyelinase-deficient Niemann-Pick type A cells. These data suggest that both the SM content and membrane distribution are crucial for pathophysiological events bringing therapeutic perspective in the role of SM membrane distribution.-Makino, A., Abe, M., Murate, M., Inaba, T., Yilmaz, N., Hullin-Matsuda, F., Kishimoto, T., Schieber, N. L., Taguchi, T., Arai, H., Anderluh, G., Parton, R. G., Kobayashi, T. Visualization of the heterogeneous membrane distribution of sphingomyelin associated with cytokinesis, cell polarity, and sphingolipidosis.The FASEB Journal 11/2014; 29(2). DOI:10.1096/fj.13-247585 · 5.48 Impact Factor
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ABSTRACT: Venomics research is being revolutionized by the increased use of sensitive -omics techniques to identify venom toxins and their transcripts in both well studied and neglected venomous taxa. The study of neglected venomous taxa is necessary both for understanding the full diversity of venom systems that have evolved in the animal kingdom, and to robustly answer fundamental questions about the biology and evolution of venoms without the distorting effect that can result from the current bias introduced by some heavily studied taxa. In this review we draw the outlines of a roadmap into the diversity of poorly studied and understood venomous and putatively venomous invertebrates, which together represent tens of thousands of unique venoms. The main groups we discuss are crustaceans, flies, centipedes, non-spider and non-scorpion arachnids, annelids, molluscs, platyhelminths, nemerteans, and echinoderms. We review what is known about the morphology of the venom systems in these groups, the composition of their venoms, and the bioactivities of the venoms to provide researchers with an entry into a large and scattered literature. We conclude with a short discussion of some important methodological aspects that have come to light with the recent use of new -omics techniques in the study of venoms.Toxins 12/2014; 6(12):3488-3551. DOI:10.3390/toxins6123488 · 2.48 Impact Factor