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Erythrocyte membrane abnormalities in sickle cell disease.
P Williamson1, E Puchulu, M Westerman
1Amherst College, Massachusetts 01002.
Biotechnology and Applied Biochemistry
|October 1, 1990
Summary
Sickle red blood cells contain large, calcium-rich vesicles, likely causing elevated cellular calcium. Abnormal, slow endocytosis in sickle cells may generate these vesicles, contributing to disease pathology.
Area of Science:
- Hematology
- Cell Biology
- Biochemistry
Background:
- Sickle red blood cells (RBCs) exhibit elevated intracellular calcium (Ca2+).
- Circulating sickle RBCs contain large vesicles not found in normal erythrocytes.
- These vesicles are rich in Ca2+ and plasma membrane Ca2+-ATPase, with Ca2+ leakage via a nitrendipine-sensitive pathway.
Purpose of the Study:
- To investigate whether an abnormal endocytic process in sickle cells generates the Ca2+-containing vesicles.
- To determine the source of elevated Ca2+ levels in sickle RBCs.
Main Methods:
- Utilized the nonspecific endocytic marker Lucifer yellow (LY) to assess endocytosis in sickle cells.
- Compared endocytosis kinetics and vesicle formation in sickle cells versus normal and sickle reticulocytes.
- Examined the number of cells exhibiting endocytosis with nonspecific versus receptor-mediated markers.
Main Results:
- Sickle cells displayed a slow component of LY-labeled endocytic vesicle formation, absent in normal or sickle reticulocytes.
- A greater number of sickle cells showed endocytosis with the nonspecific marker compared to receptor-mediated markers.
- These findings suggest a distinct, abnormal endocytic pathway in sickle cells.
Conclusions:
- A slow, abnormal endocytosis occurs in sickle red blood cells.
- This abnormal endocytosis is a potential source of the Ca2+-rich vesicles found in sickle cells.
- The formation of these vesicles may explain the characteristic elevated Ca2+ levels in sickle cell disease.