Abstract 277: Prominent Role for the Gap Junction Protein Connexin37 in Hemostasis and Thrombosis
Formation of platelet plug initiates hemostasis at sites of vascular injury, and triggers pathological thrombosis in ischemic tissue disease. Although various crucial molecules for platelet function have been identified in recent years, the mechanisms of inter- and intra-cellular signaling leading to the formation of a stable platelet plug is still poorly understood. Connexins form gap junctions, clusters of intercellular channels that are known to synchronize responses in multi-cellular organisms through the direct exchange of ions, small metabolites and other second messenger molecules between adjacent cells. Here, we report the expression of the gap junction protein connexin37 (Cx37) in mouse and human platelets. In addition, we observed functional gap junction communication between platelets during platelet aggregation in vitro, as assessed by microinjection of the gap junction-permeable tracer neurobiotin in platelets isolated from human or wild-type mice. In contrast, the tracer did not spread within the platelet aggregates obtained from Cx37-deficient mice (N=4). To assess hemostasis and thrombosis in mice in vivo, we have transsected the tail of Cx37-deficient and control mice and obtained significant differences in the cessation of bleeding: bleeding time was 3.8 ± 0.5 min for Cx37−/− mice and 8.8 ± 1.4 min for Cx37+/+controls (mean ± SEM, N=20, P<0.005). In agreement with this data, we also observed remarkable differences in the time of survival after inducing thrombo-embolism by injecting a collagen/epinephrine into the jugular vein of these two groups of mice: control mice survived 4.2 ± 0.4 min and Cx37−/ − mice only 1.9 ± 0.3 min (mean ± SEM, N=8, P<0.001). Taken together, our results demonstrate that Cx37 plays a crucial role in the physiological and pathological signaling in platelets leading to hemostasis and thrombosis. We hypothesize that gap junctions synchronize responses in platelets brought in close contact during their activation, likely by transmitting intracellular signals to neighboring cells.