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Phospholipid rearrangement of apoptotic membrane does not depend on nuclear activity
1Centro di Citometria, Istituto di Scienze Morfologiche, Università di Urbino, Italy.
Abstract:
The behaviour of plasma membrane was studied in UV-treated cells to investigate its involvement in apoptosis. It was studied in HL60 cells, in which DNA oligonucleosomic cleavage occurs, and in Molt-4 cells, which are characterised by a different fragmentation pattern. During the early stages of apoptosis, a membrane lipid rearrangement occurs, which involves phosphatidylserine translocation from the inner to the outer leaflet. This molecular alteration was investigated by annexin V-FITC binding, analysed by flow cytometry and confocal microscopy. It was correlated with transmission electron microscopy, subdiploid peak appearance and DNA fragmentation. Our data indicate that the plasma membrane represents an early apoptotic target, even if its alterations are not detectable by ultrastructural analysis, which indicates its good preservation until late apoptotic stages. In addition, the study of apoptotic cells with absent or inactivated endonuclease demonstrates the independence of this membrane mechanism from nuclear activity.
Insights
The plasma membrane is an early target in apoptosis, showing lipid rearrangements even before nuclear DNA fragmentation. This membrane alteration is independent of nuclear endonuclease activity.
Area of Science:
- Cell Biology
- Molecular Biology
- Apoptosis Research
Background:
- Apoptosis, or programmed cell death, involves complex cellular changes.
- The role of the plasma membrane in early apoptosis is not fully understood.
- Previous studies have focused on nuclear events during apoptosis.
Purpose of the Study:
- To investigate the behavior of the plasma membrane during UV-induced apoptosis.
- To determine if plasma membrane alterations are an early event in apoptosis.
- To assess the independence of plasma membrane changes from nuclear activity.
Main Methods:
- Studied UV-treated HL60 and Molt-4 cells.
- Utilized annexin V-FITC binding assay analyzed by flow cytometry and confocal microscopy.
- Correlated findings with transmission electron microscopy, subdiploid DNA content, and DNA fragmentation.
Main Results:
- Observed phosphatidylserine translocation to the outer leaflet of the plasma membrane during early apoptosis.
- Plasma membrane alterations were detected prior to ultrastructural changes and significant DNA fragmentation.
- Membrane lipid rearrangement occurred independently of nuclear endonuclease activity.
Conclusions:
- The plasma membrane is an early and sensitive target in the apoptotic process.
- Plasma membrane changes, specifically lipid rearrangement, precede nuclear events.
- This membrane mechanism is independent of nuclear endonuclease activity, highlighting its early role in apoptosis.