Antibody cross-linking of human platelet P-selectin induces calcium entry by a mechanism dependent upon Fcgamma receptor IIA.
It is established that antibody-induced cross-linking of platelet surface receptors is able to activate platelets in a manner dependent upon FcgammaRIIA. This has not, however, previously been shown for the adhesion receptor P-selectin, and since there is evidence that P-selectin may couple to activation events, it was important to address whether antibody cross-linking of this receptor induced signalling events, and whether this was dependent on FcgammaRIIA. Here we show that although addition of soluble P-selectin ligand rPSGL-Ig alone is not able to induce calcium signalling, further addition of a full-length rabbit anti human IgG leads to a sustained rise in [Ca 2+ ]i. This was due to an increase in the frequency and amplitude of transient calcium spiking in single platelets. The response was dependent upon engagement of both P-selectin and FcgammaRIIA since blocking anti-bodies to either receptor inhibited the response. The calcium rise is mediated primarily by induction of a calcium entry mechanism involving the Na(+)-Ca(2+) exchanger operating in reverse mode, since it was blocked by inhibitors of Na(+)-Ca(2+) exchange, bepridil and 5 mM NiCl(2).
Sathish
Jean G
JG
Department of Pharmacology, School of Medical Sciences, University Walk, Bristol, BS8 1TD, United Kingdom.
Falati
Shahrokh
S
Croce
Kevin
K
Crump
Colin
C
Furie
Barbara C
BC
Furie
Bruce
B
Poole
Alastair W
AW
D000906:Antibodies / Q000494:pharmacology*; D015703:Antigens, CD / Q000502:physiology*; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D003432:Cross-Linking Reagents; D006801:Humans; D007074:Immunoglobulin G / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000494:pharmacology; D019007:P-Selectin / Q000276:immunology / Q000502:physiology*; D017452:Receptors, IgG / Q000502:physiology*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism
D000906:Antibodies; D015703:Antigens, CD; D003432:Cross-Linking Reagents; C080568:Fc gamma receptor IIA; D007074:Immunoglobulin G; D008562:Membrane Glycoproteins; D019007:P-Selectin; C084882:P-selectin ligand protein; D017452:Receptors, IgG; D019831:Sodium-Calcium Exchanger; D002118:Calcium