Molecular Analysis of the Plasma Protein Reelin in Platelet Function and Coagulation Activation

Haemotasis is a vital process to prevent exceeded blood loss from injury and is properly regulated by interplays among platelet, coagulation cascade and vascular constriction. Recent studies from our laboratory revealed that a plasma protein Reelin may have functional implication in platelets. Our preliminary data further indicate that Reelin is a substrate of the coagulation factors thrombin and FXa. Moreover, Reelin interacts with the phospholipids phosphatidylserine (PS) that is present in the outer membrane of activated platelets. Consistent with these observations, Reelin-deficient mice displayed a prolonged bleeding time with an increase in rebleeding rate. In addition, fibrin clot structure is not in a normal density when coagulation was induced using Reelin-deficient plasma. Based on the aforementioned experimental evidence, we hypothesize that there are functional interplays between Reelin, coagulation factors, and platelets. We propose to test this hypothesis within the next three years. In the first and second year, we will perform comprehensive analysis of Reelin-deficient mice regarding the coagulation and haemostasis function. In particular, the assays of calibrated automated thrombogram and thrombelastography will be performed. We will also investigate the molecular basis for the cleavage of Reelin by thrombin and FXa as well as the other coagulation factors in both extrinsic and intrinsic pathways to obtain insight regarding the specificity of Reelin cleavage by individual coagulation factor. In addition, the molecular basis for the interactions between Reelin and PS as well as between Reelin and platelet surface will be determined. In the third year, we will determine Reelin function in haemostasis and in particular the effects of Reelin cleavage on the interaction between Reelin and platelet/PS. Moreover, whether Reelin plays an important role in FXa-mediated prothrombin cleavage will be analyzed. The accomplishment of this proposal may shed new insight in Reelin function and the regulatory mechanisms involved in the activation of coagulation cascade and in the control of haemostasis.

Project ID:PC10301-0136
External Project ID:NSC102-2628-B182-010-MY3