Actin type and distribution in erythrocytes

Erythrocytes transport oxygen from the lungs to the tissues. The excess surface area together with the elasticity of the erythrocyte cell membrane provides the flexibility needed to pass through the microvasculature where the oxygen exchange occurs. Although the architecture of the red cell and its membrane-associated cytoskeletal network is known in general, the factors that control the characteristic shape change during echinocyte formation are poorly understood. In this short report we show that in echinocytes a completely reorganized membrane cytoskeleton with a box-like structure of actin filaments prevailed indicating the importance of the actin cytoskeleton during echinocyte formation. The red blood cell membrane is an elastic shell with remarkable properties. Peripheral erythrocytes are cell remnants, since they have lost their nuclei, cytoplasmic organelles and are no longer able to synthesize proteins and to proliferate. However, they are absolutely essential for the survival of any macro organism with a blood circulation, because they transport the majority of the necessary oxygen to the cells of the body. Human erythrocytes circulate in the body for about 120 days and are normally discocytes with a biconcave shape and a diameter of ∼7.5 mm, a surface area of ∼140 mm2 and a volume of ∼100 mm3 [1]. The excess surface area of erythrocytes (allowing the flattened shape under resting conditions), together with the elasticity of their membranes, provides them with the flexibility needed to pass through very small capillaries with diameters as small as 2-3 mm [2, 3]). The erythrocyte membrane consists of a phospholipid bilayer with embedded membrane proteins and an underlying membrane cytoskeleton.