Early membrane events in polymorphonuclear cell (PMN) apoptosis: membrane blebbing and vesicle release, CD43 and CD16 down-regulation and phosphatidylserine externalization.
CD43 down-regulation during the apoptosis of PMN (polymorphonuclear cells) is not caused by proteolysis or internalization. Could it be released with bleb-derived membrane vesicles? Membrane blebbing was followed by microscopy on PMN 'synchronized' by an overnight incubation at 15 degrees C before their spontaneous apoptosis at 37 degrees C. Released vesicles were quantified by flow cytometry. Membrane blebbing, release of bleb-derived membrane vesicles, decrease of CD43/CD16 expression and phosphatidylserine externalization occurred simultaneously. However, caspase and PKC inhibition prevented annexin binding but not blebbing, vesicle release or CD43 expression decrease; myosin light chain kinase inhibition prevented cell blebbing and vesicle release but had no effect on CD43/CD16 down-regulation or annexin V binding. By electron microscopy, CD43 appeared poorly expressed on membrane blebs and concentrated at bleb 'necks'. In conclusion, CD43 down-regulation is not caused by cell blebbing. Cell blebbing, phospholipid 'flip-flop' and CD43/CD16 down-regulation are independent membrane events.
Nusbaum
P
P
INSERM U 507 Hôpital Necker, Paris, France.
Lainé
C
C
Seveau
S
S
Lesavre
P
P
Halbwachs-Mecarelli
L
L
D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis*; D017209:Apoptosis; D002462:Cell Membrane / Q000473:pathology*; D002469:Cell Separation; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D051917:Leukosialin; D009504:Neutrophils / Q000473:pathology*; D010718:Phosphatidylserines / Q000378:metabolism*; D017452:Receptors, IgG / Q000096:biosynthesis*; D012795:Sialoglycoproteins / Q000096:biosynthesis*; D015398:Signal Transduction; D013696:Temperature
D015703:Antigens, CD; D004791:Enzyme Inhibitors; D051917:Leukosialin; D010718:Phosphatidylserines; D017452:Receptors, IgG; C465014:SPN protein, human; D012795:Sialoglycoproteins