Platelet apoptosis by cold-induced glycoprotein Ibα clustering.

Abstract

Cold-storage of platelets followed by rewarming induces changes in Glycoprotein (GP) Ibα-distribution indicative of receptor clustering and initiates thromboxane A(2) -formation. GPIbα is associated with 14-3-3 proteins, which contribute to GPIbα-signaling and in nucleated cells take part in apoptosis regulation. We investigated whether GPIbα-clustering induces platelet apoptosis through 14-3-3 proteins during cold (4 h 0 °C)-rewarming (1 h 37 °C). During cold-rewarming, 14-3-3 proteins associate with GPIbα and dissociate from Bad inducing Bad-dephosphorylation and activation. This initiates pro-apoptosis changes in Bax/Bcl-x(L) and Bax-translocation to the mitochondria, inducing cytochrome c release. The result is activation of caspase-9, which triggers phosphatidylserine exposure and platelet phagocytosis by macrophages. Responses are prevented by N-acetyl-D-glucosamine (GN), which blocks GPIbα-clustering, and by O-sialoglycoprotein endopeptidase, which removes extracellular GPIbα. Cold-rewarming triggers apoptosis through a GN-sensitive GPIbα-change indicative of receptor clustering. Attempts to improve platelet transfusion by cold-storage should focus on prevention of the GPIbα-change.