Antibody cross-linking of human platelet P-selectin induces calcium entry by a mechanism dependent upon Fcγ receptor IIA

Abstract

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).

Involvement of Platelet–Tumor Cell Interaction in Immune Evasion. Potential Role of Podocalyxin-Like Protein 1

“…In that way, binding of PSGL-1 to P-selectin expressed on platelets induces calcium influx and a signaling cascade that triggers α IIb β 3 activation, microaggregates generation, and thrombus formation (85, 86). Platelet activation is followed by the phosphorylation of tyrosine, serine, threonine, and histidine residues on the cytoplasmic tail of P-selectin (87–89).…”