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Sticholysins are α-pore-forming toxins produced by the sea-anemone Stichodactyla helianthus. These toxins exert their activity by forming pores on sphingomyelin-containing membranes. Recognition of sphingomyelin by sticholysins is required to start the process of pore formation. Sphingomyelin recognition is coupled with membrane binding and followed by membrane penetration and oligomerization. Many features of these processes are known. However, the extent of contact with each of the different kinds of lipids present in the membrane has received little attention. To delve into this question, we have used a phosphatidylcholine analogue labeled at one of its acyl chains with a doxyl moiety, a known quencher of tryptophan emission. Here we present evidence for the contact of sticholysins with phosphatidylcholine lipids in the sticholysin oligomer, and for how each sticholysin isotoxin is affected differently by the inclusion of cholesterol in the membrane. Furthermore, using phosphatidylcholine analogs that were labeled at different positions of their structure (acyl chains and headgroup) in combination with a variety of sticholysin mutants, we also investigated the depth of the tryptophan residues of sticholysins in the bilayer. Our results indicate that the position of the tryptophan residues relative to the membrane normal is deeper when cholesterol is absent from the membrane. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new synthetic route of ceramide 1-phosphate affords a series of analogs containing modifications in the hydrophilic structure suitably and straightforwardly. • Surface plasmon response disclose that amide, 3-OH and phosphate groups of ceramide-1-phosphate stabilize the specific interaction with cytosolic phospholipase A 2 α. • Dihydro-ceramide 1-phosphate has a higher affinity towards cytosolic phospholipase A 2 α. Ceramide 1-phosphate (C1P) is a lipid mediator that specifically binds and activates cytosolic phospholipase A 2 α (cPLA 2 α). To elucidate the structure–activity relationship of the affinity of C1P for cPLA 2 α in lipid environments, we prepared a series of C1P analogs containing structural modifications in the hydrophilic parts and subjected them to surface plasmon resonance (SPR). The results suggested the presence of a specific binding site for cPLA 2 α on the amide, 3-OH and phosphate groups in C1P structure. Especially, dihydro-C1P exhibited enhanced affinity for cPLA 2 α, suggesting the hydrogen bonding ability of 3-hydroxy group is important for interactions with cPLA 2 α. This study helps to understand the influence of specific structural moieties of C1P on the interaction with cPLA 2 α at the atomistic level and may lead to the design of drugs that regulate cPLA 2 α activation. [ABSTRACT FROM AUTHOR]

And by UCM-Banco Santander Grants PR75/18-21561, PR87/19-22556, and PR108/20-26896 (to A.M.-d.-P.)." now reads: "This research was supported by the Juselius Foundation (J.P.S. and J.P.-O.) And by UCM-Banco Santander Grants PR75/18-21561, PR87/19-22556, PR108/20-26896 and a REACT-EU grant from the Comunidad de Madrid to the ANTICIPA prorogued project of Complutense University of Madrid (to A.M.-d.-P.).". [Extracted from the article]

Actinoporins constitute a family of α pore-forming toxins produced by sea anemones. The soluble fold of these proteins consists of a β-sandwich flanked by two α-helices. Actinoporins exert their activity by specifically recognizing sphingomyelin at their target membranes. Once there, they penetrate the membrane with their N-terminal α-helices, a process that leads to the formation of cation-selective pores. These pores kill the target cells by provoking an osmotic shock on them. In this review, we examine the role and relevance of the structural features of actinoporins, down to the residue level. We look at the specific amino acids that play significant roles in the function of actinoporins and their fold. Particular emphasis is given to those residues that display a high degree of conservation across the actinoporin sequences known to date. In light of the latest findings in the field, the membrane requirements for pore formation, the effect of lipid composition, and the process of pore formation are also discussed. • Actinoporins share a common soluble fold. • The actinoporin fold is exquisitely selected for sphingomyelin recognition. • Sticholysins' behavior depends on membrane composition and access to sphingomyelin. • Cholesterol greatly enhances sticholysin activity. [ABSTRACT FROM AUTHOR]

Ganglioside GM3 in the plasma membranes suppresses cell growth by preventing the autophosphorylation of the epidermal growth factor receptor (EGFR). Biological studies have suggested that GM3 interacts with the transmembrane segment of EGFR. Further biophysical experiments are particularly important for quantitative evaluation of the peptide-glycolipid interplay in bilayer membranes using a simple reconstituted system. To examine these interactions in this way, we synthesized the transmembrane segment of EGFR bearing a nitrobenzoxadiazole fluorophore (NBD-TM) at the N-terminus. The affinity between EGFR and GM3 was evaluated based on Förster resonance energy transfer (FRET) between NBD-TM and ATTO594-labeled GM3 in bilayers where their non-specific interaction due to lateral proximity was subtracted by using NBD-labeled phospholipid. This method for selectively detecting the specific lipid-peptide interactions in model lipid bilayers disclosed that the lateral interaction between GM3 and the transmembrane segment of EGFR plays a certain role in disturbing the formation of active EGFR dimers. [Display omitted] • FRET discloses lateral interaction of a glycolipid with helical peptide in membrane. • Dimerization of EGF receptor transmembrane peptide is partially disturbed by GM3. • GM3 interacts EGF receptor transmembrane peptide having preferable tilt angle. • Extracellular domain close to the membrane relates to the ganglioside selectivity. [ABSTRACT FROM AUTHOR]