Loss of zinc transporters ZIP1 and ZIP3 augments platelet reactivity in response to G protein-coupled receptor agonists and accelerates thrombus formation in vivo

Zinc (Zn2+) is considered as an important mediator for thrombosis and haemostasis. However, our understanding of the transport mechanisms that regulate Zn2+ homeostasis in platelets is limited. Zn2+ transporters, ZIPs and ZnTs, are widely expressed in eukaryotic cells. Using mice globally lacking ZIP1 and ZIP3 (ZIP1/3 DKO), our aim was to explore the potential role of these well-known Zn2+ transporters in maintaining platelet Zn2+ homeostasis and in the regulation of platelet function. While ICP-MS measurements indicated unaltered overall Zn2+ concentrations in platelets of ZIP1/3 DKO mice, we observed a significantly delayed and less efficient Zn2+ release upon thrombin-stimulated platelet activation. This resulted in a hyperactive platelet response not only in response to thrombin, but also towards other G protein-coupled receptor (GPCR) agonists. Immunoreceptor tyrosine-based activation (ITAM)-coupled receptor agonist signalling, however, was unaffected. Augmented GPCR responses were accompanied by enhanced Ca2+ signalling and PKC activation. Further functional analysis of ZIP1/3 double deficient mice revealed enhanced platelet aggregation, bigger thrombus volume under flow ex vivo and faster in vivo thrombus formation. The current study thereby identifies ZIP1 and ZIP3 as important regulators for the maintenance of platelet Zn2+ homeostasis and function.