CalDAG-GEFI integrates signaling for platelet aggregation and thrombus formation.
Signaling through the second messengers calcium and diacylglycerol (DAG) is a critical element in many biological systems. Integration of calcium and DAG signals has been suggested to occur primarily through protein kinase C family members, which bind both calcium and DAG. However, an alternative pathway may involve members of the CalDAG-GEF/RasGRP protein family, which have structural features (calcium-binding EF hands and DAG-binding C1 domains) that suggest they can function in calcium and DAG signal integration. To gain insight into the signaling systems that may be regulated by CalDAG-GEF/RasGRP family members, we have focused on CalDAG-GEFI, which is expressed preferentially in the brain and blood. Through genetic ablation in the mouse, we have found that CalDAG-GEFI is crucial for signal integration in platelets. Mouse platelets that lack CalDAG-GEFI are severely compromised in integrin-dependent aggregation as a consequence of their inability to signal through CalDAG-GEFI to its target, the small GTPase Rap1. These results suggest that analogous signaling defects are likely to occur in the central nervous system when CalDAG-GEFI is absent or compromised in function.[1]References
- CalDAG-GEFI integrates signaling for platelet aggregation and thrombus formation. Crittenden, J.R., Bergmeier, W., Zhang, Y., Piffath, C.L., Liang, Y., Wagner, D.D., Housman, D.E., Graybiel, A.M. Nat. Med. (2004) [Pubmed]
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