On the evolution of erythrocyte programmed cell death: apoptosis of Rana esculenta nucleated red blood cells involves cysteine proteinase activation and mitochondrion permeabilization.

Batracian Rana esculenta erythrocytes cell death induced by either calcium influx, or staurosporine, involves typical apoptotic phenotype. Our data reveal: (i) a drastic modification of the cell morphology with loss of the ellipsoidal form as assessed by phase contrast microscopy and scanning electron microscopy; (ii) an exposure of the phosphatidylserine residues in the outer leaflet of the cell membrane; (iii) a caspase-3-like activity; (iv) a mitochondrial membrane potential (Delta Psi m) loss; and (v) a chromatin condensation and fragmentation. Erythrocyte chromatin condensation and fragmentation are prevented by caspase and calpain peptide inhibitors. These inhibitors also prevent Delta Psi m loss supporting the idea that mitochondria is a central sensor for Rana erythrocytes cell death. Our observations highlight the conservation of the programmed cell death machinery in erythrocytes across kingdom.

Uptake of sialic acid by human erythrocyte. Characterization of a transport system.

Upon incubation of human red blood cells (RBC) with [4-9-14C] N-acetylneuraminic acid, the cells incorporated this sugar, as demonstrated by the identification of labelled N-acetylmannosamine in the cytosol, as a result of the action of the sialic acid pyruvate-lyase we discovered previously (Biochimie 84 (2002) 655). The mechanism is saturable and indicates the presence of a limited number of transporter molecules in the RBC membrane. This transport process may have relevance to the desialylation of membrane glycoconjugates which occurs during ageing of erythrocytes.