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Staphylocidal action of thrombin-induced platelet microbicidal protein is not solely dependent on transmembrane
1Department of Medicine, Division of Infectious Diseases, St. John's Cardiovascular Research Center, LAC-Harbor UCLA Medical Center, Torrance, California 90509, USA.
Abstract:
Thrombin-induced platelet microbicidal protein (tPMP) is a small, cationic, antimicrobial peptide released from rabbit platelets when stimulated with thrombin. We studied the relationship between staphylococcal transmembrane potential (delta psi) and tPMP staphylocidal activity. A genetically related pair of Staphylococcus aureus strains, 6850 and JB1, which differ in delta psi generation (-143 and -97 mV, respectively) were used. Mutant JB-1 was substantially less susceptible to tPMP than the parental strain, 6850. Menadione supplementation, which normalized the delta psi of strain JB-1, did not restore JB-1 tPMP susceptibility. These findings suggest that the staphylocidal activities of tPMP require factors other than or in addition to an intact delta psi.
Insights
Thrombin-induced platelet microbicidal protein (tPMP) exhibits antimicrobial activity against Staphylococcus aureus. However, its effectiveness is not solely dependent on the bacterial transmembrane potential (delta psi).
Area of Science:
- Microbiology
- Biochemistry
- Immunology
Background:
- Thrombin-induced platelet microbicidal protein (tPMP) is a cationic antimicrobial peptide derived from rabbit platelets.
- Antimicrobial peptides often target bacterial membranes, with transmembrane potential (delta psi) being a key factor in their activity.
Purpose of the Study:
- To investigate the relationship between staphylococcal transmembrane potential (delta psi) and the antimicrobial activity of tPMP.
- To determine if delta psi is the sole determinant of tPMP efficacy against Staphylococcus aureus.
Main Methods:
- Utilized a genetically related pair of Staphylococcus aureus strains (6850 and JB1) with differing delta psi generation.
- Assessed tPMP susceptibility in both strains.
- Supplemented the less susceptible strain (JB-1) with menadione to normalize delta psi.
Main Results:
- Staphylococcus aureus strain JB-1, with a lower delta psi, demonstrated significantly reduced susceptibility to tPMP compared to strain 6850.
- Menadione supplementation normalized the delta psi of strain JB-1 but did not restore its susceptibility to tPMP.
Conclusions:
- The staphylocidal activity of tPMP is not exclusively dependent on an intact staphylococcal transmembrane potential (delta psi).
- Additional factors, beyond delta psi, are likely involved in the mechanism of tPMP action against Staphylococcus aureus.