Molecular link between membrane cholesterol and Na+/H+ exchange within human platelets

FEBS Letters

Kochhar, N.¹  Kaul, D.¹ 

[1] Molecular Biology Unit, Department of Experimental Medicine, P.G.I.M.E.R., Chandigarh, India

关键词: Cholesterol;    Na+/H+ exchange;    Phospholipase A2;    Platelet;   

DOI  :  10.1016/0014-5793(92)80090-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Incubation of human platelets with cholesterol-poor, cholesterol-normal and cholesterol-rich liposomes revealed that: (i) acquisition or depletion of platelet membrane cholesterol was highly selective; (ii) variation in membrane cholesterol was highly selective. Variation in membrane cholesterol content (cholesterol-to-phospholipid molar ratio from 0.15–1.2) with respect to values found in unmodified normal platelets, was paralleled by the observed changes in amiloride-sensitive cytoplasmic pH, as well as phospholipase A₂ activity. However, a decrease in cytoplasmic pH was accompanied by an increase in phospholipase A₂ activity; (iii) membrane cholesterol-modulated changes in intra-platelet pH, as well as phospholipase A₂ activity, was completely inhibited when platelets were pretreated with quinacrine (a specific phospholipase A₂ inhibitor) before exposure to various types of liposomes. Although exposure of platelets (pretreated with amiloride) with various types of liposomes resulted in the inhibition of Na⁺/H⁺ exchange it had no noticeable effect upon the observed phospholipase A₂ activity. Based upon these results we suggest that membrane cholesterol-modulated phospholipase A₂ activity may be the basic mechanism responsible for the nature of Na⁺/H⁺ exchanger activity observed in cholesterol-enriched platelets, leading these platelets to a hypersensitized state.

【 授权许可】

Unknown