Na+/H+ antiporter has different properties in human B lymphocytes according to CD5 expression and malignant phenotype.
In B chronic lymphocytic leukemia (B-CLL) cells, lipopolysaccharide (LPS) and phorbol esters fail to activate the plasma membrane-associated Na+/H+ antiporter and, subsequently, to elicit a rise in cytosolic pH. Since these events are thought to be a prerequisite for LPS-induced proliferation of B normal lymphocytes, we analyzed the kinetic properties of Na+/H+ antiporter in B-CLL cells as compared to both CD5- and CD5+ normal B lymphocytes. In the present work we report that Na+/H+ exchange rate after acid loading is drastically decreased in B-CLL cells, as compared to normal CD5- B lymphocytes, although the antiporter affinity for external Na+ and internal H+ is not significantly different in both cell populations. Kinetic data account for a reduction in the number of operating antiport units in B-CLL. The Na+/H+ antiporter of CD5+ normal B lymphocytes exhibits both an exchange rate and an ion affinity significantly higher than that observed in both CD5+ B-CLL cells and CD5- B normal lymphocytes, thus suggesting a possible explanation for their activated phenotype.
Ghigo
D
D
Dipartimento di Genetica, Universitá di Torino, Italy.
Gaidano
G
G
Treves
S
S
Bussolino
F
F
Pescarmona
G
G
Caligaris-Cappio
F
F
Bosia
A
A
D015703:Antigens, CD / Q000032:analysis*; D000943:Antigens, Differentiation / Q000032:analysis*; D016175:B-Lymphocyte Subsets / Q000378:metabolism*; D018956:CD5 Antigens; D002352:Carrier Proteins / Q000378:metabolism*; D002469:Cell Separation; D005455:Fluorescent Antibody Technique; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D016393:Lymphoma, B-Cell / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers; D014407:Tumor Cells, Cultured
D015703:Antigens, CD; D000943:Antigens, Differentiation; D018956:CD5 Antigens; D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium