Membrane protein segregation during release of microvesicles from human erythrocytes

Quantitative composition and characterization of the proteins in membrane vesicles released from erythrocytes by dimyristoylphosphatidylcholine. A membrane system without cytoskeleton

“…When this process reaches a certain extent, protein segregation begins [45]. The most mobile components of the membrane preferentially diffuse into destorted membrane areas, whereas components which are restricted in their lateral mobility, eg, by interaction with the cytoskeleton, are retarded.…”

The isolation and characterization of 60 nm vesicles (‘nanovesicles’) produced during ionophore A23187-induced budding of human erythrocytes

“…In particular, the microvesicles contain no spectrin (bands 1 and 2) or actin (band 5)*, which are prominent components of the normal erythrocyte membrane. Shukla and his colleagues (Shukla et al, 1978) have extended these observations to show that of the two major membrane polypeptides that do remain in the microvesicles (bands 3 and 4.1), one of these (band 4.1) appears to reside in a curious membranous appendage ('tail') to each microvesicle that is often observed in electron micrographs (Allan et al, 1976;Shukla et al, 1978) and that can be detached by sonication. Shukla et al (1978) and Allan & Mitchell (1979b) have suggested that segregation of polypeptide 4.1 into this 'tail' region may be significant in the membrane fusion process that leads Abbreviation used: Hepes, 4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid.…”

“…The work described in the present paper provides evidence for spontaneous release of dense vesicles even smaller than microvesicles that may be derived from those regions of the erythrocyte membrane that undergo fusion during the budding process. Surprisingly, in view of the results of Shukla et al (1978) these 'nanovesicles' contain polypeptides 4.5 (mol.wt. 60000) and 8 (mol.wt.…”

Erythrocyte Membrane Vesiculation and Changes in Membrane Composition during Storage in Citrate-Phosphate-Dextrose-Adenine-1

“…The accumu lation of 1, 2-diacylglycerol formed by the action of a Ca2+-activated phospholipase on phosphatidylcholine (PC) in the outer leaflet of the membrane was suggested as the mech anism of the exocytosis [5], Subsequent workers have questioned the validity of this hypothesis because sheep red cells which contain no PC act similarly [30,31] and because vésiculation can be produced in the presence of EGTA with no added Ca2+ [32]. More recently, evidence has been presented that the diacylglycérol is formed by the ac tion of a Ca2+-activated phosphodiesterase on phosphatidylinositol phosphate and phosphatidylinositol diphosphate [33][34][35], Most recently, the role of Ca2+ in the shape transformation which follows ATP deple tion has also been questioned [36], A num ber of studies using conditions which cause rapid depletion of ATP and simulated blood bank conditions have established the forma tion of 60-200-nm vesicles [6][7][8]37].…”