Monoclonal anti-CD23 antibodies induce a rise in [Ca2+]i and polyphosphoinositide hydrolysis in human activated B cells. Involvement of a Gp protein.
Transduction through the CD23 molecule (Fc epsilon RII) was analyzed in human activated B lymphocytes using anti-CD23 mAb. B cell blasts expressing an increased amount of surface CD23 molecule were obtained by stimulation of normal peripheral blood B lymphocytes with Staphylococcus aureus strain Cowan I and IL-4. Anti-CD23 mAb were found to trigger polyphosphoinositide hydrolysis in these cells (and also in tumoral B cells expressing spontaneously CD23) and a rise in [Ca2+]i which could be attributed to mobilization from cytoplasmic pools. This increase in [Ca2+]i could be mimicked, with a comparable time-course, by the addition of InsP3 to permeabilized B cell blasts indicating that the increase in inositol phosphate accumulation induced by the antibodies was due to a preferential attack of phosphatidylinositol-bisphosphate by a specific phosphoinositidase C (PIC). In permeabilized cells, raising the free calcium concentration above 3 microM was found to induce polyphosphoinositides hydrolysis and to activate directly the PIC. Addition of 100 microM GTP-tetralithium salt, a non-hydrolyzable analogue of GTP, also resulted in an increased accumulation of inositol phosphates. A Ca2(+)-dependent PIC, linked to a GTP-binding protein (Gp protein), can thus be activated in B cell blasts. Addition of anti-CD23 antibodies to permeabilized B cells in the presence of a physiologic concentration of Ca2+ (100 nM) evoked, within 10 min, a rise in the various inositol phosphates. This ability of anti-CD23 antibodies to activate PIC was enhanced in the presence of GTP-tetralithium salt 100 microM. By contrast, preincubation with GDP-trilithium salt, a nonhydrolyzable analogue of GDP, caused a marked reduction in the release of inositol phosphates. Preincubation of B cell blasts with Pertussis toxin resulted in a total inhibition of the capacity of the toxin to ADP-ribosylate a 41-kDa protein, probably of the Gi type; in these conditions, no modification of anti-CD23-elicited polyphosphoinositide hydrolysis could be detected. These results suggest that the CD23 molecule may be coupled to the phosphoinositide signaling pathway by a GTP-dependent component that is insensitive to Pertussis toxin.
Kolb
J P
JP
U. 196 INSERM Recherche sur les Interférons, Paris, France.
Renard
D
D
Dugas
B
B
Genot
E
E
Petit-Koskas
E
E
Sarfati
M
M
Delespesse
G
G
Poggioli
J
J
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000911:Antibodies, Monoclonal; D000944:Antigens, Differentiation, B-Lymphocyte / Q000502:physiology*; D001402:B-Lymphocytes / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism; D008213:Lymphocyte Activation; D037342:Pertussis Toxin; D010716:Phosphatidylinositols / Q000378:metabolism*; D011961:Receptors, Fc / Q000502:physiology*; D017455:Receptors, IgE; D015398:Signal Transduction; D013873:Thionucleotides / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D000944:Antigens, Differentiation, B-Lymphocyte; D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D011961:Receptors, Fc; D017455:Receptors, IgE; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D002118:Calcium