VLK is important for thrombus formation in vivo. VLK is primarily stored in α-granules of platelets and is released upon activation. It is crucial for exocytosis of dense granules; however, the precise mechanism is unknown. VLK also acts as an extracellular kinase and can result in autocrine and paracrine substrate phosphorylation (P). VLK is important for platelet aggregation and supports fibrin deposition.