Release of vesicles enriched in complement receptor 1 from human erythrocytes.
Vesicles released from human E by Ca(2+)-loading, ATP-depletion, or storage are enriched in several glycosylphosphatidylinositol-anchored proteins such as acetylcholinesterase (AchE) and decay-accelerating factor (DAF). As a result of this, the remaining E are depleted of these proteins. We analyzed whether vesiculation induced by ATP-depletion in vitro was also responsible for a loss of C receptor 1 (CR1), which is a transmembrane protein arranged predominantly in small clusters. ATP-depleted E had lost 15.4% to 33.9% of their CR1. This loss was similar to that of AchE and DAF. The released vesicles contained CR1. The number of CR1 per band 3 protein was 1.7 to 2.7 that in the original E, indicating an enrichment of CR1 in vesicles. This enrichment was similar to that observed for AchE and DAF (1.83- and 2.6-fold, respectively). The capacity of the vesicles and the ATP-depleted E to bind C3b-coated immune complexes correlated with the CR1 number, suggesting that there was no preferential loss of CR1 clusters. Vesicles released from human E during C attack also contained CR1. In conclusion, in vitro aging induced by ATP-depletion is responsible not only for a loss of glycosylphosphatidylinositol-anchored proteins, but also of CR1. Whether vesiculation explains the loss of CR1 from aging E in vivo and from E of patients with SLE or AIDS remains to be studied.
Pascual
M
M
Laboratory of Immunonephrology, Centre Médical Universitaire, Geneva, Switzerland.
Lutz
H U
HU
Steiger
G
G
Stammler
P
P
Schifferli
J A
JA
D000255:Adenosine Triphosphate / Q000097:blood; D000328:Adult; D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism; D003165:Complement System Proteins / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D017463:Receptors, Complement 3b / Q000378:metabolism*
D001457:Anion Exchange Protein 1, Erythrocyte; D017463:Receptors, Complement 3b; D000255:Adenosine Triphosphate; D003165:Complement System Proteins