Cardiovascular disease (CVD) is the number one killer of mankind. Most CVDs are associated with atherosclerosis and thrombosis. It is well documented that platelets are the initiators of both atherosclerosis and thrombosis. Platelets are maintained in resting state in the circulation by endogenous negative regulators to avoid unintentional activation. During vascular injury, pro- stimulatory signals override anti-stimulatory signals to achieve rapid platelet activation. Lot of research is focused on pro-stimulatory signals while little is known about negative regulators. We have shown that JAM-A is an endogenous suppressor of platelet activation. Ablation of JAM-A confers an augmentation of in vivo thrombosis. However, upon platelet activation what happens to JAM-A is not known. We hypothesize that JAM-A forms a dimer upon dissociation from the integrin complex and support junctional assembly at the platelet?platelet junctions through the activation of Rap1. This R01 proposal is focused on delineating the role of JAM-A in initiating platelet-platelet junction formation, and thus preventing blood loss through the wound. Accordingly, three Specific Aims have been proposed.
Specific Aim 1 will test the hypothesis that platelet JAM-A associates with the integrin through CD9, a tetraspanin, by forming a multi- protein complex in a PDZ-domain-dependent manner. We will use biochemical, mutational and genetic approaches to identify the components of this complex.
Specific Aim 2 will test the hypothesis that upon platelet activation JAM-A dimerizes and assembles Rap1-activating complex to achieve Rap1 activation during outside-in signaling. We will use biochemical, mutational and genetic approaches to delineate the molecular mechanism that regulate JAM-A- dependent Rap1 activation.
Specific Aim 3 will test the hypothesis that JAM-A is responsible in recruiting junctional proteins at the platelet-platelet contacts to assemble functional junctions. We will use genetically modified cells and mice to evaluate the role of JAM-A and other known junctional proteins in regulating permeability of hemostatic plug using in vitro and in vivo assays. Successful completion of this proposal will help to understand the role of junctional adhesion molecules in hemostasis and to develop therapeutic interventions for thrombosis associated diseases such as atherosclerosis, MI, and stroke.

Public Health Relevance

Platelets play an important part in initiating cardiovascular diseases such as myocardial infarction and stroke. Controlling platelet activation is very important for combating CVD complications. It is particularly important to identify new targets for combating platelet reactivity to reduce CVD. Delineating the molecular mechanisms of platelet activation and function is the first step towards developing novel therapeutic interventions to combat CVD.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
2R01HL119374-06A1
Application #
9819416
Study Section
Hemostasis and Thrombosis Study Section (HT)
Program Officer
Ochocinska, Margaret J
Project Start
2013-08-01
Project End
2023-06-30
Budget Start
2019-08-15
Budget End
2020-06-30
Support Year
6
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Thomas Jefferson University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
053284659
City
Philadelphia
State
PA
Country
United States
Zip Code
19107
Patel, P; Golla, K; Naik, U P (2018) PDK1 governs thromboxane generation and thrombosis in platelets by regulating activation of Raf1 in the MAPK pathway: comment. J Thromb Haemost 16:1901-1904
Naik, Meghna U; Caplan, Jeffrey L; Naik, Ulhas P (2014) Junctional adhesion molecule-A suppresses platelet integrin ?IIb?3 signaling by recruiting Csk to the integrin-c-Src complex. Blood 123:1393-402
Lathia, Justin D; Li, Meizhang; Sinyuk, Maksim et al. (2014) High-throughput flow cytometry screening reveals a role for junctional adhesion molecule a as a cancer stem cell maintenance factor. Cell Rep 6:117-29
Chatterjee, Sharmila; Wang, Yan; Duncan, Melinda K et al. (2013) Junctional adhesion molecule-A regulates vascular endothelial growth factor receptor-2 signaling-dependent mouse corneal wound healing. PLoS One 8:e63674
Aravindan, Rolands G; Fomin, Victor P; Naik, Ulhas P et al. (2012) CASK interacts with PMCA4b and JAM-A on the mouse sperm flagellum to regulate Ca2+ homeostasis and motility. J Cell Physiol 227:3138-50
Naik, Meghna U; Stalker, Timothy J; Brass, Lawrence F et al. (2012) JAM-A protects from thrombosis by suppressing integrin ?IIb?3-dependent outside-in signaling in platelets. Blood 119:3352-60
Lakshmi, Sowmya P; Reddy, Aravind T; Naik, Meghna U et al. (2012) Effects of JAM-A deficiency or blocking antibodies on neutrophil migration and lung injury in a murine model of ALI. Am J Physiol Lung Cell Mol Physiol 303:L758-66