To date, all of the known activators of platelets and hemostasis are soluble and cell matrix molecules. The Kahn lab has demonstrated that interactions between podoplanin (PDPN), a transmembrane protein, and CLEC-2 receptors on the surface of platelets prevent blood-lymphatic mixing throughout life. This pathway requires platelet activation by CLEC2. Studies from the Kahn lab reveal the basis for this phenotype to be a novel form of platelet-mediated hemostasis at the lympho-venous junction that is stimulated by CLEC2 interaction with lymphatic endothelial PDPN. The Bergmeier lab has recently collaborated with the Kahn lab to demonstrate that platelet CLEC2 signaling is also required for hemostasis during vascular inflammation in the lung and skin. The proposed studies will address these new biological roles of PDPN-CLEC2 platelet activation, and investigate the mechanism by which CLEC2 signaling in platelets mediates such non-canonical hemostatic responses.
Aim 1 will investigate the role of PDPN-CLEC2 signaling in preventing pulmonary and inflammatory hemorrhage, two very recently identified functions of this platelet activation pathway.
Aim 2 will test whether this pathway participates in platelet responses to vessel wall injury, determine the mechanism by which the pathway prevents hemorrhage during inflammation, and identify the platelet mechanisms that protect the lymphatic network through lympho- venous hemostasis. These studies will define a recently discovered platelet activation pathway that performs hemostatic roles not previously associated with platelet activation that are highly relevant for human disease.

Public Health Relevance

This proposal investigates the role of a new platelet activation pathway. In this pathway cells that express the surface protein PDPN activate the platelet receptor CLEC2. We have found this pathway to be required for types of hemostasis that are not considered typical, platelet driven hemostasis. These include inter-vascular hemostasis required for blood-lymphatic vascular separation and hemostasis during tissue inflammation. We will use mouse genetic approaches to further study this novel type of hemostasis and platelet function in the context of human diseases.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL121650-01A1
Application #
8761615
Study Section
Hemostasis and Thrombosis Study Section (HT)
Program Officer
Kindzelski, Andrei L
Project Start
2014-09-01
Project End
2018-06-30
Budget Start
2014-09-01
Budget End
2015-06-30
Support Year
1
Fiscal Year
2014
Total Cost
Indirect Cost
Name
University of Pennsylvania
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
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Sevivas, Teresa; Bastida, José María; Paul, David S et al. (2018) Identification of two novel mutations in RASGRP2 affecting platelet CalDAG-GEFI expression and function in patients with bleeding diathesis. Platelets 29:192-195
Cook, Aaron A; Deng, Wei; Ren, Jinqi et al. (2018) Calcium-induced structural rearrangements release autoinhibition in the Rap-GEF CalDAG-GEFI. J Biol Chem 293:8521-8529
Stefanini, Lucia; Bergmeier, Wolfgang (2018) RAP GTPases and platelet integrin signaling. Platelets :1-7
Bermejo, Emilse; Alberto, Maria F; Paul, David S et al. (2018) Marked bleeding diathesis in patients with platelet dysfunction due to a novel mutation in RASGRP2, encoding CalDAG-GEFI (p.Gly305Asp). Platelets 29:84-86
Stefanini, Lucia; Lee, Robert H; Paul, David S et al. (2018) Functional redundancy between RAP1 isoforms in murine platelet production and function. Blood 132:1951-1962
Casari, Caterina; Paul, David S; Susen, Sophie et al. (2018) Protein kinase C signaling dysfunction in von Willebrand disease (p.V1316M) type 2B platelets. Blood Adv 2:1417-1428
Paul, David S; Casari, Caterina; Wu, Congying et al. (2017) Deletion of the Arp2/3 complex in megakaryocytes leads to microthrombocytopenia in mice. Blood Adv 1:1398-1408
Battram, Anthony M; Durrant, Tom N; Agbani, Ejaife O et al. (2017) The Phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3) Binder Rasa3 Regulates Phosphoinositide 3-kinase (PI3K)-dependent Integrin ?IIb?3 Outside-in Signaling. J Biol Chem 292:1691-1704
Ren, Jinqi; Cook, Aaron A; Bergmeier, Wolfgang et al. (2016) A negative-feedback loop regulating ERK1/2 activation and mediated by RasGPR2 phosphorylation. Biochem Biophys Res Commun 474:193-198

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