Reelin is important for PLCgamma2 phosphorylation upon platelet activation and integrin outside-in signaling

I. Krueger, M. Klier, N. S. Gowert, M. Elvers (Duesseldorf, Germany)

Date: 18.02.2017,
Time: 10:00 - 11:15

Objective: Reelin is an important mediator for cell migration in brain development. Recent studies provide evidence that Reelin is found in plasma and platelet-alpha-granules and plays an important role in platelet activation. Furthermore Reelin expression was also reported to increase upon inflammatory processes. This and the findings in reeler mice showing reduced thrombus formation under high shear conditions ex vivo and protection against arterial thrombosis in vivo prompted further investigation regarding the exact Reelin-mediated signaling pathways, especially regarding the cytoskeletal reorganization following platelet activation and adhesion.

Methods: In vitro and in vivo analysis of mutant Reelin deficient mice to investigate Reelin mediated signaling cascades in platelets.

Results: Reelin activated small GTPases of the Rho family and is important for the phosphorylation of Rho target proteins such as PAK1/2 supporting lamellipodia formation upon spreading on fibrinogen. Moreover, adhesion and cytoskeletal reorganization of reeler platelets on a collagen-related peptide (CRP) matrix was reduced. In line with this result platelet activation in response to CRP was strongly reduced in Reelin deficient platelets. Engagement of glycoprotein (GP)VI induced robust phosphorylation of PLCgamma2 and Syk while significantly reduced phosphorylation was detected using platelets from reeler mice. To analyze integrin outside-in signaling in further detail, clot retraction experiments were performed showing almost absent clot formation of Reelin deficient platelets. Thus we found Reelin effecting GPVI dependent signaling and integrin outside-in signaling suggesting that Reelin modulates PLCgamma2 activation.

Conclusion: This study identifies Reelin as an important mediator in hemostasis and arterial thrombosis showing great promise for a therapeutic target in antithrombotic treatments.