The effect of cholesterol on the long-range network of interactions established among sea anemone Sticholysin II residues at the water-membrane interface.

Sara García-Linares,Álvaro Martínez-Del-Pozo,Ida Alm,José Gavilanes,Johan Slotte,Terhi Maula

doi:10.3390/md13041647

Sara García-Linares, Álvaro Martínez-Del-Pozo + Show 4 more

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https://doi.org/10.3390/md13041647

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Abstract

Actinoporins are α-pore forming proteins with therapeutic potential, produced by sea anemones. Sticholysin II (StnII) from Stichodactyla helianthus is one of its most extensively characterized members. These proteins remain stably folded in water, but upon interaction with lipid bilayers, they oligomerize to form a pore. This event is triggered by the presence of sphingomyelin (SM), but cholesterol (Chol) facilitates pore formation. Membrane attachment and pore formation require changes involving long-distance rearrangements of residues located at the protein-membrane interface. The influence of Chol on membrane recognition, oligomerization, and/or pore formation is now studied using StnII variants, which are characterized in terms of their ability to interact with model membranes in the presence or absence of Chol. The results obtained frame Chol not only as an important partner for SM for functional membrane recognition but also as a molecule which significantly reduces the structural requirements for the mentioned conformational rearrangements to occur. However, given that the DOPC:SM:Chol vesicles employed display phase coexistence and have domain boundaries, the observed effects could be also due to the presence of these different phases on the membrane. In addition, it is also shown that the Arg51 guanidinium group is strictly required for membrane recognition, independently of the presence of Chol.

Highlights

Sea anemones are a group of benthic marine animals which secrete various toxins [1] including a group of small and basic α-pore forming proteins known as actinoporins [2]
All far-UV circular dichroism (CD) spectra of the individual mutants were indistinguishable from that corresponding to the wild-type Sticholysin II (StnII)
The results presented here reveal the influence of this lipid on the essential long-distance rearrangements required for pore-formation, since the StnII variants that were studied harbor mutations that affect residues in protein regions with assigned key roles in pore formation (Figures 1 and 5)

Summary

Introduction

Sea anemones are a group of benthic marine animals which secrete various toxins [1] including a group of small and basic α-pore forming proteins known as actinoporins [2]. These actinoporins form cation-selective pores on the cell membranes, causing colloid-osmotic shock that leads to cells death [3,4,5]. They are believed to participate in anemone functions such as predation, defense, and digestion, and have been shown to be lethal to small crustaceans, mollusks, fish [6], and parasites [7]. Like many other marine toxins, actinoporins show some therapeutic potential, including different pharmacological effects, presumable anticancer activities, and use in the construction of specific immunotoxins [1,7,13,14,15,16,17,18]

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