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CalDAG-GEFI integrates signaling for platelet aggregation and thrombus formation

Nature Medicine volume 10, pages 982986 (2004) | Download Citation

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  • An Erratum to this article was published on 01 October 2004

Abstract

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 integration1,2. 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 blood1. 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.

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Acknowledgements

We are grateful to B. Roe for providing a BAC clone of CalDAG-GEFI; T. Kinashi for providing antibodies to RapL; M. Yaffe for critical reading of the manuscript; R. Shivdasani and R. Hynes for advice; and P. Harlan for technical support. This work was funded by National Institute of Child Health and Development grant R01-HD28341 (A.M.G.); the James and Pat Poitras Research Fund (A.M.G.); the Grace B. Kerr Fund (A.M.G.); the Angus & Monaise MacDonald Fund (A.M.G.); National Institutes of Mental Health grant F32-MH065815 (J.R.C.); a grant from the Deutsche Forschungsgemeinschaft (W.B.); and the National Heart, Lung, and Blood Institute of the National Institutes of Health grants P01-HL56949 (D.D.W.) and HL66105 (D.E.H.).

Author information

Author notes

    • Jill R Crittenden
    •  & Wolfgang Bergmeier

    These authors contributed equally to this work.

Affiliations

  1. Department of Brain and Cognitive Sciences, and McGovern Institute for Brain Research, Massachusetts Institute of Technology, 45 Carleton Street, E25-618, Cambridge, Massachusetts 02139, USA.

    • Jill R Crittenden
    • , Yanyu Zhang
    •  & Ann M Graybiel
  2. The CBR Institute for Biomedical Research and the Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA.

    • Wolfgang Bergmeier
    • , Crystal L Piffath
    •  & Denisa D Wagner
  3. Department of Immunology, University of Washington, Box 357370, Seattle, Washington 98195, USA.

    • Yuqiong Liang
  4. Center for Cancer Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.

    • Jill R Crittenden
    •  & David E Housman

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Competing interests

The Massachusetts Institute of Technology has filed a patent application on behalf of J.R.C., A.M.G. and D.E.H., “The Use of Protein Inhibitors as Antithrombotic Agents,” case no. 10198 filed with the US Patent Office on June 2, 2003. The protein referred to in the patent application is that described in this manuscript, CalDAG-GEFI.

Corresponding author

Correspondence to Ann M Graybiel.

Supplementary information

PDF files

  1. 1.

    Supplementary Fig. 1

    Aggregation assays in response to calcium ionophore A23187.

  2. 2.

    Supplementary Table 1

    Clotting factor assays in CalDAG-GEFT−/− mice.

  3. 3.

    Supplementary Table 2

    Blood cell counts in CalDAG-GEFT−/− mice.

Videos

  1. 1.

    Supplementary Video 1

    Platelets in whole blood from CalDAG-GEFI knockout mice do not form thrombi on a collagen surface. Real-time movies of platelets perfused over a collagen plate. a, wild-type calcein-labeled platelets, and b, CalDAG-GEFI−/− calcein-labeled platelets.

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DOI

https://doi.org/10.1038/nm1098