Anti-glycophorin C induces mitochondrial membrane  depolarization and a loss of extracellular regulated kinase 1/2  protein kinase activity that is prevented by pretreatment with  cytochalasin D: implications for hemolytic disease of the fetus  and newborn caused by anti-Ge3.
BACKGROUND
Anti-glycophorin C (GPC), blood group antibodies of which cause hemolytic disease of the fetus and newborn (HDFN), is a potent inhibitor of erythroid progenitor cell growth. The cellular mechanism for growth inhibition has not been characterized.


METHODS
K562 cells were incubated in the presence of either anti-GPC, an immunoglobulin G isotype control, an inhibitor of actin polymerization called cytochalasin D with anti-GPC, or cytochalasin D alone. The JC-1 cationic dye was used to detect mitochondrial depolarization and the activity of the mitogen-activated protein kinases was assessed by Western blotting.


RESULTS
Anti-GPC inhibits the activity of extracellular regulated kinase (ERK)1/2 within 10 minutes but does not alter the activity of p38 or c-Jun N-terminal kinase. After 24 hours there was a significant loss of mitochondrial membrane potential compared to isotype control–treated cells. Both the ERK1/2 inhibition and the loss of mitochondrial potential were prevented by pretreatment with cytochalasin D.


CONCLUSIONS
A cell surface antibody can cause anemia by altering the signaling pathways in erythroid cells by promoting depolarization of mitochondria via cytoskeletal rearrangement. The observation that neonates with anti-GPC HDFN are unresponsive to erythropoietin can be explained by the antibody inhibiting a protein kinase through which this hematopoietic growth factor achieves its effects.
Micieli
Jonathan A
JA
Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario,Canada.
Wang
Duncheng
D
Denomme
Gregory A
GA
D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D015638:Cytochalasin D / Q000494:pharmacology*; D004899:Erythroblastosis, Fetal / Q000209:etiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D006021:Glycophorins / Q000276:immunology*; D006801:Humans; D007231:Infant, Newborn; D020014:K562 Cells; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects* / Q000502:physiology
D000911:Antibodies, Monoclonal; D006021:Glycophorins; D015638:Cytochalasin D; D048049:Extracellular Signal-Regulated MAP Kinases