The Role of Zinc and Junctional Adhesion Molecule A Protein in Platelet Plug Formation

Background: The coagulation cascade depends on the active participation of several elements present in the blood as well as signals arising from the endothelial cells. A platelet plug is a temporary, fast-response seal formed by platelets at the site of a damaged blood vessel to initiate hemostasis. Among the changes platelets undergo is the degranulation step. Platelet degranulation results in the release of substances like ADP, serotonin, fibrinogen, and zinc. Currently, zinc's targets are unknown. Methods: Platelet-to-platelet aggregation relies on specific surface receptors and plasma bridge proteins. Such mechanistic elements have been extensively studied (i.e., αIIbβ3 integrin). In this work, using platelet aggregation methods and recombinant proteins, we will expand the repertoire of proteins relevant to platelet plug formation. Particularly, size-exclusion chromatography (SEC), surface plasmon resonance (SPR), and transmission electron microscopy (TEM) were mainly used. Using 1 mM zinc and 10 µM ADP, we evaluated platelet aggregation and proteins responsible for this aggregation's behavior in response to zinc release from platelets' granules upon activation. SPR provided results to evaluate the affinity of our target proteins on the surface of platelets when influenced by the increase in zinc after degranulation. Results: In the present work, we provide evidence that the high local concentration of zinc is intended to target junctional adhesion molecule A (JAM-A), which remains inactive (inhibiting cell-adhesion and cytoskeleton dynamics) when coagulation is not needed, and platelets move through the bloodstream as single units. Zinc-activated JAM-A leads the platelets to aggregate. Our experimentation includes work with platelets and a synthetic biology small peptide to quench the effects of zinc. Conclusions: JAM-A interacts with zinc to aid in the formation of the platelet plug. This interaction activates the cell-adhesion and cytoskeleton dynamics functions of JAM-A. We suggest that further exploring this mechanism of zinc-activated JAM-A can be advantageous for understanding hemostasis, its role in antithrombotic therapy, coagulation inhibition, or thrombosis prevention.