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Updated: Jul 19, 2026
Fluorescence-Based Measurements of Phosphatidylserine/Phosphatidylinositol 4-Phosphate Exchange Between Membranes
Published on: March 14, 2021
Phospholipase A activity associated with the growth of Rickettsia prowazekii in L929 cells
1Department of Microbiology and Immunology, University of South Alabama College of Medicine, Mobile 36688.
Abstract:
Cultured L929 cells infected with Rickettsia prowazekii had a greatly increased rate of hydrolysis of fatty acid from the oleic acid-radiolabeled phospholipids of the host cell membranes. The incorporation of fatty acid into phospholipid in an infected cell was only moderately inhibited relative to a mock-infected cell. Thus, even if the release of fatty acid from phospholipid represented a steady state between hydrolysis and resynthesis of phospholipids, the increase in release of fatty acid was due principally to increased phospholipase A activity. The increased rate of hydrolysis did not occur only late in the rickettsial infection; this activity began early in infection and continued throughout the course of infection. The addition of tetracycline or chloramphenicol (antibiotics which inhibit rickettsial protein synthesis) to the infected cells caused a rapid and total abatement of this increased rate of phospholipid hydrolysis. In contrast, high concentrations of penicillin affected the morphology of the intracellular rickettsiae, but did not inhibit the phospholipase activity. This phospholipase A activity clearly damages the host cell during the rickettsial infection and may represent the activity by which R. prowazekii escapes from the host cell.
Insights
Rickettsia prowazekii infection significantly increases host cell membrane phospholipase A activity, leading to fatty acid release. This damage is reversed by antibiotics inhibiting bacterial protein synthesis.
Area of Science:
- Cell Biology
- Microbiology
- Biochemistry
Background:
- Rickettsia prowazekii is an obligate intracellular bacterium causing epidemic typhus.
- Host cell membrane integrity is crucial for pathogen survival and host cell function.
- Mechanisms of host cell damage during Rickettsia infection are not fully understood.
Purpose of the Study:
- To investigate the effect of Rickettsia prowazekii infection on host cell membrane phospholipid metabolism.
- To identify the specific enzymatic activity responsible for observed changes.
- To determine the role of this activity in the Rickettsia-host cell interaction.
Main Methods:
- Cultured L929 cells were infected with Rickettsia prowazekii.
- Oleic acid-radiolabeling was used to trace fatty acid incorporation and hydrolysis in phospholipids.
- Effects of antibiotics (tetracycline, chloramphenicol, penicillin) on phospholipase activity were assessed.
Main Results:
- Infected cells showed a greatly increased rate of fatty acid hydrolysis from host cell phospholipids.
- Fatty acid incorporation into phospholipids was only moderately inhibited.
- Increased hydrolysis was attributed to enhanced phospholipase A activity, present early and throughout infection.
- Tetracycline and chloramphenicol rapidly abolished this activity, while penicillin did not.
- This phospholipase A activity contributes to host cell damage and potential R. prowazekii escape.
Conclusions:
- Rickettsia prowazekii infection induces significant host cell phospholipase A activity.
- This bacterial-induced enzymatic activity damages host cell membranes.
- The phospholipase A activity is essential for Rickettsia pathogenesis and may facilitate bacterial egress.
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