The goal of this proposal is to define the intracellular signaling pathways that contribute to the synthesis of phosphorylated phosphatidylinositols (phosphoinositides) in platelets, and to understand the role of phosphoinositides in platelet biology. Our recent research has focused on the synthesis of two phosphatidylinositol bisphosphates, PtdIns(4,5)P2 and PtdIns(3,5)P2. The hypotheses underlying this proposal are that the synthesis of PtdIns(4,5)P2 and PtdIns(3,5)P2 occurs within unique microdomains in platelets, and that PtdIns(4,5)P2 and PtdIns(3,5)P2 are each responsible for discrete aspects of platelet signaling and in vivo thrombus formation. We have studied the synthesis of PtdIns(4,5)P2 by the ?, ?, and ? isoforms of phosphatidylinositol phosphate 5-kinase I (PIP5KI), and found clear evidence that spatially distinct pools of PtdIns(4,5)P2 exist in platelets and in megakaryocytes. Moreover, the loss of either PIP5KI? or PIP5KI? leads to impaired in vivo thrombosis, but for different reasons. The pool of PtdIns(4,5)P2 that is synthesized by PIP5KI? is required to form second messengers and to extend lamellipodia. In contrast, PtdIns(4,5)P2 synthesized by PIP5KI? is vital for the membranecytoskeletal dynamics and allows for stable adhesion that is resistant to shear forces. We have also found that PtdIns(3,5)P2, which is synthesized by PIKFyve, regulates the biogenesis of platelet lysosomes. Deletion of PIKFyve specifically in murine platelets leads to a platelet lysosome disorder, which remarkably is associated with inflammation and accelerated thrombus formation in vivo. Taken together, these results support the hypothesis that the synthesis of particular phosphoinositides within discrete platelet subcellular microdomains regulates specific spatially distinct intracellular signaling pathways. The proposed experiments are designed to comprehensively and systematically study how PtdIns(4,5)P2 and PtdIns(3,5)P2 production regulates the platelet cytoskeleton and lysosomes. We will also study their effect on stable platelet adhesion in vivo.
In Aim 1, we will determine how PtdIns(4,5)P2 regulates platelet membrane-cytoskeletal dynamics.
In Aim 2, we will examine the spatial regulation of PtdIns(4,5)P2 synthesis. In the final Aim, we will formally analyze how PtdIns(3,5)P2 regulates the biology of the platelet lysosome and its contribution to in vivo thrombus formation.

Public Health Relevance

PROJECT 5 - NARRATIVE Platelets and macrophages both play key roles in the pathogenesis of atherosclerosis as well as arterial thrombosis that lead to acute myocardial infarctions and strokes. This proposal will analyze a previously unrecognized link between platelet secretion and macrophage activation. A better understanding of this process will identify novel therapeutic targets that could be used to treat arterial thrombosis, the most common cause of morbidity and mortality in the US.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Program Projects (P01)
Project #
1P01HL120846-01A1
Application #
8742313
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
$451,429
Indirect Cost
$169,286
Name
University of Pennsylvania
Department
Type
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Mirramezani, M; Herbig, B A; Stalker, T J et al. (2018) Platelet packing density is an independent regulator of the hemostatic response to injury. J Thromb Haemost 16:973-983
Capitano, Maegan; Zhao, Liang; Cooper, Scott et al. (2018) Phosphatidylinositol transfer proteins regulate megakaryocyte TGF-?1 secretion and hematopoiesis in mice. Blood 132:1027-1038
Branchford, B R; Stalker, T J; Law, L et al. (2018) The small-molecule MERTK inhibitor UNC2025 decreases platelet activation and prevents thrombosis. J Thromb Haemost 16:352-363
Bergmeier, Wolfgang; Stefanini, Lucia (2018) Platelets at the Vascular Interface. Res Pract Thromb Haemost 2:27-33
Zhao, Baobing; Mei, Yang; Cao, Lan et al. (2018) Loss of pleckstrin-2 reverts lethality and vascular occlusions in JAK2V617F-positive myeloproliferative neoplasms. J Clin Invest 128:125-140
Yago, Tadayuki; Zhang, Nan; Zhao, Liang et al. (2018) Selectins and chemokines use shared and distinct signals to activate ?2 integrins in neutrophils. Blood Adv 2:731-744
Stefanini, L; Bergmeier, W (2018) Negative regulators of platelet activation and adhesion. J Thromb Haemost 16:220-230
Xie, Zhigang; Hur, Seong Kwon; Zhao, Liang et al. (2018) A Golgi Lipid Signaling Pathway Controls Apical Golgi Distribution and Cell Polarity during Neurogenesis. Dev Cell 44:725-740.e4
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
Welsh, J D; Poventud-Fuentes, I; Sampietro, S et al. (2017) Hierarchical organization of the hemostatic response to penetrating injuries in the mouse macrovasculature. J Thromb Haemost 15:526-537

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