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Mutations resulting in resistance to polyene antibiotics decrease voltage-sensitive calcium channel activity in
Abstract:
In this report, the isolation of Paramecium tetraurelia mutants resistant to the polyene antibiotics amphotericin B and filipin are described. These antibiotics are known to specifically interact with membrane sterols to produce a cytotoxic effect. Four mutants resistant to amphotericin B and two mutants resistant to filipin have been isolated. In each case, an individual mutant shows resistance to both amphotericin B and filipin. Genetic analysis indicates that all 6 mutations map to the same complementation group and are not allelic to any of the 3 pawn mutations or to either of the two "barium shy" mutations. The behavioral analysis suggests that these mutations cause an alteration of normal ion channel function. Direct electrophysiological analysis of one mutant indicates mutations to polyene antibiotic resistance cause a specific decrease in voltage-sensitive Ca2+ channel activity.
Insights
Researchers isolated Paramecium tetraurelia mutants resistant to polyene antibiotics like amphotericin B and filipin. These mutations alter ion channel function, specifically decreasing calcium channel activity.
Area of Science:
- Cell Biology
- Genetics
- Pharmacology
Background:
- Polyene antibiotics, such as amphotericin B and filipin, target membrane sterols, leading to cell death.
- Understanding resistance mechanisms to these antibiotics is crucial for their therapeutic applications and biological studies.
Purpose of the Study:
- To isolate and characterize Paramecium tetraurelia mutants exhibiting resistance to amphotericin B and filipin.
- To investigate the genetic basis and functional consequences of polyene antibiotic resistance in Paramecium.
Main Methods:
- Isolation of drug-resistant mutants using selective pressure with amphotericin B and filipin.
- Genetic mapping to determine complementation groups and allelism with known mutations.
- Behavioral assays and electrophysiological recordings to assess ion channel function.
Main Results:
- Six mutants (4 resistant to amphotericin B, 2 to filipin) were isolated; each mutant showed cross-resistance to both antibiotics.
- All six resistance mutations mapped to a single complementation group, distinct from known pawn and barium shy mutations.
- Electrophysiological analysis revealed a specific decrease in voltage-sensitive Ca2+ channel activity in a resistant mutant.
Conclusions:
- The identified mutations confer resistance to polyene antibiotics by altering membrane sterol interactions or downstream signaling.
- These findings suggest a link between polyene antibiotic sensitivity and voltage-sensitive Ca2+ channel function in Paramecium.
- The study provides a valuable genetic tool for exploring the roles of specific ion channels in cellular processes and drug responses.