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Plasma membrane Ca(2+)-ATPase sulfhydryl modifications: implication for oxidized red cell
Namphaung Pengpanichpakdee1, Tanapon Thadtapong, Saranya Auparakkitanon
1Department of Biochemistry, Faculty of Science, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
The Southeast Asian Journal of Tropical Medicine and Public Health
|February 26, 2013
Summary
Oxidative stress damages red blood cell calcium pumps (PMCA). Protecting these pumps from sulfhydryl and proteolytic damage is crucial for maintaining calcium homeostasis, especially in conditions like thalassemia.
Area of Science:
- Biochemistry
- Cell Biology
- Redox Biology
Background:
- Oxidative stress commonly disrupts cellular calcium (Ca2+) homeostasis.
- Human red blood cell plasma membrane Ca2+-ATPase (PMCA) is vital for maintaining Ca2+ balance.
Purpose of the Study:
- To investigate the impact of oxidative damage on human red cell PMCA activity.
- To determine the effects of sulfhydryl agents and proteolytic enzymes on PMCA function.
Main Methods:
- Assessed PMCA activity in red cell membranes using coupled enzyme assays.
- Treated membranes with sulfhydryl agents (N-ethylmaleimide, iodoacetate, diamide) and calpain.
- Measured activity in the presence and absence of calmodulin (CaM) and reversed inhibition with dithiotreitol (DTT).
Main Results:
- Sulfhydryl agents and diamide inhibited both basal and CaM-stimulated PMCA activity dose-dependently.
- Low concentrations of sulfhydryl agents inhibited basal activity, while CaM-stimulated activity remained unaffected.
- Diamide inhibition was reversible with DTT; calpain treatment increased basal activity but abolished CaM response.
Conclusions:
- Red cell PMCA is susceptible to both sulfhydryl and proteolytic damage under oxidative stress.
- Protecting PMCA from these damages is essential for preventing Ca2+ homeostasis perturbation.
- Findings have implications for red blood cells in oxidative stress conditions like thalassemia.
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