<Li> An exposure of PS can potentiate adhesion of red cells to vascular endothelial cells, effectively preventing normal transit through the microvasculature . Thus it is important that PS is maintained only in the inner leaflet of the bilayer to ensure normal blood flow in microcirculation . </Li> <Li> Both PS and phosphatidylinositol - 4, 5 - bisphosphate (PIP2) can regulate membrane mechanical function, due to their interactions with skeletal proteins such as spectrin and protein 4.1 R. Recent studies have shown that binding of spectrin to PS promotes membrane mechanical stability . PIP2 enhances the binding of protein band 4.1 R to glycophorin C but decreases its interaction with protein band 3, and thereby may modulate the linkage of the bilayer to the membrane skeleton . </Li> <P> The presence of specialized structures named "lipid rafts" in the red blood cell membrane have been described by recent studies . These are structures enriched in cholesterol and sphingolipids associated with specific membrane proteins, namely flotillins, stomatins (band 7), G - proteins, and β - adrenergic receptors . Lipid rafts that have been implicated in cell signaling events in nonerythroid cells have been shown in erythroid cells to mediate β2 - adregenic receptor signaling and increase cAMP levels, and thus regulating entry of malarial parasites into normal red cells . </P> <P> The proteins of the membrane skeleton are responsible for the deformability, flexibility and durability of the red blood cell, enabling it to squeeze through capillaries less than half the diameter of the red blood cell (7--8 μm) and recovering the discoid shape as soon as these cells stop receiving compressive forces, in a similar fashion to an object made of rubber . </P>

Where do red blood cells go to die