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Pedrera L, Ros U, Fanani ML, Lanio ME, Epand RM, García-Sáez AJ, Álvarez C. The Important Role of Membrane Fluidity on the Lytic Mechanism of the α-Pore-Forming Toxin Sticholysin I. Toxins (Basel) 2023; 15:80. [PMID: 36668899 PMCID: PMC9865829 DOI: 10.3390/toxins15010080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 01/05/2023] [Accepted: 01/07/2023] [Indexed: 01/19/2023] Open
Abstract
Actinoporins have emerged as archetypal α-pore-forming toxins (PFTs) that promote the formation of pores in membranes upon oligomerization and insertion of an α-helix pore-forming domain in the bilayer. These proteins have been used as active components of immunotoxins, therefore, understanding their lytic mechanism is crucial for developing this and other applications. However, the mechanism of how the biophysical properties of the membrane modulate the properties of pores generated by actinoporins remains unclear. Here we studied the effect of membrane fluidity on the permeabilizing activity of sticholysin I (St I), a toxin that belongs to the actinoporins family of α-PFTs. To modulate membrane fluidity we used vesicles made of an equimolar mixture of phosphatidylcholine (PC) and egg sphingomyelin (eggSM), in which PC contained fatty acids of different acyl chain lengths and degrees of unsaturation. Our detailed single-vesicle analysis revealed that when membrane fluidity is high, most of the vesicles are partially permeabilized in a graded manner. In contrast, more rigid membranes can be either completely permeabilized or not, indicating an all-or-none mechanism. Altogether, our results reveal that St I pores can be heterogeneous in size and stability, and that these properties depend on the fluid state of the lipid bilayer. We propose that membrane fluidity at different regions of cellular membranes is a key factor to modulate the activity of the actinoporins, which has implications for the design of different therapeutic strategies based on their lytic action.
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Affiliation(s)
- Lohans Pedrera
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana, La Habana CP 10400, Cuba
- Institute for Genetics and CECAD Cluster of Excellence, University of Cologne, Joseph-Stelzmann-Straße 26, 50931 Cologne, Germany
| | - Uris Ros
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana, La Habana CP 10400, Cuba
- Institute for Genetics and CECAD Cluster of Excellence, University of Cologne, Joseph-Stelzmann-Straße 26, 50931 Cologne, Germany
| | - Maria Laura Fanani
- Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba X5000HUA, Argentina
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), Facultad de Ciencias Químicas-CONICET, Córdoba X5000HUA, Argentina
| | - María E. Lanio
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana, La Habana CP 10400, Cuba
| | - Richard M. Epand
- Department of Biochemistry and Biomedical Sciences, Faculty of Health Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Ana J. García-Sáez
- Institute for Genetics and CECAD Cluster of Excellence, University of Cologne, Joseph-Stelzmann-Straße 26, 50931 Cologne, Germany
| | - Carlos Álvarez
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana, La Habana CP 10400, Cuba
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