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Fluorescence-Based Measurements of Phosphatidylserine/Phosphatidylinositol 4-Phosphate Exchange Between Membranes
Published on: March 14, 2021
Shedding of phosphatidylserine from developing erythroid cells involves microtubule depolymerization and affects
Inna Freikman1, Israel Ringel, Eitan Fibach
1Institute of Drug Research, School of Pharmacy, Hebrew University of Jerusalem, 91120 Jerusalem, Israel.
The Journal of Membrane Biology
|July 25, 2012
Summary
Phosphatidylserine (PS) externalization in red blood cells is triggered by calcium flux, while shedding is influenced by both calcium and microtubule (MT) dynamics. MT depolymerization specifically enhances PS shedding.
Area of Science:
- Cell Biology
- Membrane Biology
- Hematology
Background:
- Phosphatidylserine (PS) normally resides on the inner cell membrane leaflet but externalizes during cell aging or damage.
- PS externalization and shedding are critical processes in erythroid cell maturation, affecting red blood cell (RBC) function, senescence, and clearance.
- Evidence suggests PS shedding is linked to intracellular calcium (Ca) levels and interactions between membrane phospholipids and microtubules (MTs).
Purpose of the Study:
- To investigate how calcium flux and microtubule (MT) assembly influence phosphatidylserine (PS) distribution and shedding in erythroid precursors.
- To elucidate the roles of Ca and MTs in regulating PS externalization and shedding during erythroid cell development.
Main Methods:
- Cultured human and murine erythroid precursors were treated with the Ca ionophore A23187, paclitaxel (Taxol) to enhance MT assembly, or colchicine to inhibit MT assembly.
- Phosphatidylserine (PS) externalization and shedding were quantified using flow cytometry.
- Cholesterol and phospholipid levels in RBC membranes and supernatants were analyzed by ¹H-NMR.
Main Results:
- Both Taxol and colchicine significantly increased PS externalization.
- Colchicine enhanced PS shedding, whereas Taxol inhibited it.
- The cholesterol/phospholipid ratio in the membrane increased with colchicine and A23187 treatment, but remained unchanged with Taxol.
Conclusions:
- Calcium flux mediates PS externalization in erythroid precursors.
- Both calcium flux and MT depolymerization contribute to PS shedding.
- PS shedding alters the membrane's cholesterol/phospholipid ratio, impacting membrane composition.
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