A study of endogenous proteinaceous regulators of plasma membrane calcium-ATPase in porcine erythrocyte

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A study of endogenous proteinaceous regulators of plasma membrane calcium-ATPase in porcine erythrocyte


Author: Cheng, Chun-kwok
Title: A study of endogenous proteinaceous regulators of plasma membrane calcium-ATPase in porcine erythrocyte
Degree: M.Sc.
Year: 2003
Subject: Hong Kong Polytechnic University -- Dissertations
Calcium -- Physiological effect
Plant cell membranes
Adenosine triphosphatase
Calcium channels
Department: Dept. of Applied Biology and Chemical Technology
Pages: vii, 114 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1718578
URI: http://theses.lib.polyu.edu.hk/handle/200/936
Abstract: Plasma membrane calcium ATPase (PMCA) is an important enzyme involved in many vital regulatory processes. Alternation in erythrocyte PMCA has been observed in several diseases conditions. The purpose of this study is to evaluate the interaction of endogenous proteinaceous regulators, namely the activator calmodulin (CaM) and plasma membrane calcium-ATPase inhibitor (PMCAI), with intact porcine erythrocytes; and to see if they can be potential candidates for therapeutic use in diseases with calcium ion transport problems. Biochemical and morphological changes of intact young and old porcine erythrocytes, and endogenous proteinaceous regulators-fused porcine erythrocytes upon calcium and glucose challenges were studied in this regard. In our study, sodium-potassium-ATPase (Na+/K+-ATPase) of young porcine erythrocyte was found to be more effective than old porcine erythrocyte in pumping out sodium ion and potassium into the cell. The function of Na+/K+-ATPase is to maintain a high potassium concentration and a low sodium concentration in cytosol when cell is challenged with high extracellular calcium. Difference in calcium- ATPase activities between young and old porcine erythrocyte populations, however, was not observed. When porcine erythrocyte was fused with phosphate-buffered saline, CaM, or PMCAI, Na+/K+-ATPase of porcine erythrocyte was found still active in pumping sodium ion out and potassium into the cell. However, noticeable hemoglobin leakage and cell lysis were observed in PMCAI-fused porcine erythrocyte incubated in high calcium level at 37C for four hours indicating that PMCAI was active in inhibiting the calcium-ATPase and subsequently affected the membrane integrity. Further works have to be done to study and differentiate the effect that is purely caused by endogenous proteinaceous regulators in the cytosol, and/or in the plasma, or possibly from the lyzed membrane protein.

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