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, but not platelet aggregation mediated by integrin activation. Preliminary 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 PDPN- CLEC2 interaction. 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-arterial, 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 determine what effectors of CLEC2 signaling in platelets function during inflammation and in blood-lymphatic vascular separation. These studies will define a recently discovered platelet activation pathway that performs hemostatic roles not previously associated with platelet activation that are highly relevant to human disease.

Public Health Relevance

Principal Investigator: Charles Abrams Project 2 Narrative Mark L. Kahn 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. Wolfgang Bergmeier The scope of the work is to determine (1) how platelet CLEC2 signaling is triggered at sites of inflammation, and (2) which platelet response(s) are important for the ability of platelets to safeguard vascular integrity. Completion of these studies will define key molecular aspects of this novel form of hemostasis.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Program Projects (P01)
Project #
1P01HL120846-01A1
Application #
8742310
Study Section
Heart, Lung, and Blood Initial Review Group (HLBP)
Project Start
Project End
Budget Start
2014-08-08
Budget End
2015-06-30
Support Year
1
Fiscal Year
2014
Total Cost
$422,200
Indirect Cost
$105,000
Name
University of Pennsylvania
Department
Type
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Stalker, Timothy J; Welsh, John D; Brass, Lawrence F (2014) Shaping the platelet response to vascular injury. Curr Opin Hematol 21:410-7
Min, Sang H; Suzuki, Aae; Stalker, Timothy J et al. (2014) Loss of PIKfyve in platelets causes a lysosomal disease leading to inflammation and thrombosis in mice. Nat Commun 5:4691