Patch repair protects cells from the small pore-forming toxin aerolysin
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Updated: Aug 6, 2025
Live Imaging Assay for Assessing the Roles of Ca2+ and Sphingomyelinase in the Repair of Pore-forming Toxin Wounds
Published on: August 25, 2013
1Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA.
Abstract:
Aerolysin family pore-forming toxins damage the membrane, but membrane repair responses used to resist them, if any, remain controversial. Four proposed membrane repair mechanisms include toxin removal by caveolar endocytosis, clogging by annexins, microvesicle shedding catalyzed by MEK, and patch repair. Which repair mechanism aerolysin triggers is unknown. Membrane repair requires Ca2+, but it is controversial if Ca2+ flux is triggered by aerolysin. Here, we determined Ca2+ influx and repair mechanisms activated by aerolysin. In contrast to what is seen with cholesterol-dependent cytolysins (CDCs), removal of extracellular Ca2+ protected cells from aerolysin. Aerolysin triggered sustained Ca2+ influx. Intracellular Ca2+ chelation increased cell death, indicating that Ca2+-dependent repair pathways were triggered. Caveolar endocytosis failed to protect cells from aerolysin or CDCs. MEK-dependent repair did not protect against aerolysin. Aerolysin triggered slower annexin A6 membrane recruitment compared to CDCs. In contrast to what is seen with CDCs, expression of the patch repair protein dysferlin protected cells from aerolysin. We propose aerolysin triggers a Ca2+-dependent death mechanism that obscures repair, and the primary repair mechanism used to resist aerolysin is patch repair. We conclude that different classes of bacterial toxins trigger distinct repair mechanisms.
Insights
Aerolysin toxins harm cells, but patch repair, not other mechanisms, helps cells survive. This calcium-dependent process involves specific repair proteins, distinct from other toxin responses.
Area of Science:
- Cellular biology
- Toxicology
- Membrane biophysics
Background:
- Aerolysin toxins damage cell membranes, but the specific repair mechanisms cells employ remain unclear.
- Proposed repair pathways include endocytosis, annexins, MEK-dependent shedding, and patch repair, but their roles against aerolysin are debated.
- The necessity and triggering of calcium (Ca2+) influx during aerolysin-induced membrane damage are controversial.
Purpose of the Study:
- To investigate Ca2+ influx and identify membrane repair mechanisms activated by aerolysin.
- To compare aerolysin's effects with those of cholesterol-dependent cytolysins (CDCs) regarding membrane repair.
Main Methods:
- Assessed cell survival upon removal of extracellular Ca2+.
- Measured Ca2+ influx and intracellular Ca2+ chelation effects.
- Evaluated the roles of caveolar endocytosis, MEK-dependent repair, annexin A6 recruitment, and dysferlin in aerolysin resistance.
Main Results:
- Extracellular Ca2+ removal protected cells from aerolysin, unlike CDCs.
- Aerolysin induced sustained Ca2+ influx, and its chelation increased cell death, indicating Ca2+-dependent repair activation.
- Caveolar endocytosis and MEK-dependent repair did not protect against aerolysin.
- Dysferlin expression conferred protection against aerolysin, suggesting patch repair is involved.
Conclusions:
- Aerolysin triggers a Ca2+-dependent cell death pathway that may mask repair mechanisms.
- Patch repair, involving proteins like dysferlin, is proposed as the primary mechanism resisting aerolysin.
- Different bacterial toxin classes activate distinct cellular membrane repair strategies.
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