Inflammation; vitamin K-dependent protein; Gas6; Protein S; Hemostasis
Prince Raja, Bologna Luca, Manetti Mirko, Melchiorre Daniela, Rosa Irene, Dewarrat Natacha, Suardi Silvia, Amini Poorya, Fernández José A, Burnier Laurent, Quarroz Claudia, Reina Caro Maria Desiré, Matsumura Yasuhiro, Kremer Hovinga Johanna A, Griffin John H, Simon Hans-Uwe, Ibba-Manneschi Lidia, Saller François, Calzavarini Sara, Angelillo-Scherrer Anne (2018), Targeting anticoagulant protein S to improve hemostasis in hemophilia., in Blood
Ridger V. C., Boulanger C. M., Angelillo-Scherrer A., Badimon L., Blanc-Brude O., Bochaton-Piallat M.-L., Boilard E., Buzas E. I., Caporali A., Dignat-George F., Evans P. C., Lacroix R., Lutgens E., Ketelhuth D. F. J., Nieuwland R., Toti F., Tunon J., Weber C., Hoefer I. E. (2017), Microvesicles in vascular homeostasis and diseasesPosition Paper of the European Society of Cardiology (ESC) Working Group on Atherosclerosis and Vascular Biology, in Thrombosis and Haemostasis
, 117(7), 1296-1316.
Stalder Grégoire, Que Yok Ai, Calzavarini Sara, Burnier Laurent, Kosinski Christophe, Ballabeni Pierluigi, Roger Thierry, Calandra Thierry, Duchosal Michel A., Liaudet Lucas, Eggimann Philippe, Angelillo-Scherrer Anne (2016), Study of Early Elevated Gas6 Plasma Level as a Predictor of Mortality in a Prospective Cohort of Patients with Sepsis, in PLOS ONE
, 11(10), e0163542-e0163542.
Happonen Kaisa E., Tran Sinh, Mörgelin Matthias, Prince Raja, Calzavarini Sara, Angelillo-Scherrer Anne, Dahlbäck Björn (2016), The Gas6-Axl Protein Interaction Mediates Endothelial Uptake of Platelet Microparticles, in Journal of Biological Chemistry
, 291(20), 10586-10601.
We intend to further study the role of growth arrest-specific gene 6 (Gas6) and protein S (Pros), their mechanism of action and the possible therapeutic use of Gas6 agonists or antagonists in medically important -often lifethreatening- conditions such as bleeding, thrombosis and inflammation. Gas6 belongs to the vitamin K-dependent protein family. Apart from a ?-carboxyglutamic acid-domain interaction with phospholipid membranes, Gas6 also binds as a ligand to the receptor tyrosine kinases Tyro3, Axl and Mer (or TAM receptors) by its carboxy-terminal globular domains. We became interested in Gas6 because of its sequence homology with the anticoagulant Pros. Pros is well recognized as an important natural anticoagulant. This is evidenced by the increased risk of thromboembolic events (recurrent deep vein thrombosis at adult age) in heterozygous patients deficient in Pros. Notably homozygous Pros deficiency is associated with dramatic clinical manifestations (disseminated intravascular coagulation, purpura fulminans) and, if untreated, is incompatible with life. Current knowledge on the biological functions of Pros is only limited, although a number of in vitro studies have helped elucidate the structure/function relationships of Pros.Even though our initial studies of the Gas6 gene inactivation did not reveal any “spontaneous” phenotype, detailed analyses of these mice have unveiled that Gas6 plays an “amplifier” role in hemostasis where it is redundant for baseline hemostasis but critical for effective platelet aggregation upon vascular injury -precisely by amplifying the platelet aggregation activity of the classical agonists. Similarly, we found very recently that Gas6 amplifies erythropoietin responses during compensatory erythropoietic response to anemia. Thus, Gas6 belongs to a novel class of molecules, which are redundant for normal homeostasis but critical for stress-responses. Not surprisingly, therefore, inactivation of Gas6 does not cause life-threatening developmental defects, but may importantly modulate the severity of disease related phenotypes.The first part of the project aims at a better understanding of the in vivo role of Pros in mice. We recently described the lethal prothrombic phenotype of Pros-/- mice. To circumvent the problem of life incompatibility and thereby extend the field of our investigations, mice with very low levels of Pros will be generated. Mice with consistently lower Pros levels would be viable while presenting a much stronger phenotype than that of Pros+/- mice. Such mice would be very helpful to investigate new biological functions for Pros. Two experimental approaches have been chosen: 1) the selective repression of Pros expression in the liver parenchymal cells which is expected to result in dramatic reduction of circulating Pros levels, as Pros is mainly expressed in the liver; 2) the repression of Pros expression in adult mice. Another elegant way to circumvent the embryonically lethal phenotype of Pros-/- mice would be to generate mice with total deficiency in Pros but expressing high levels of activated protein C (APC) or low tissue factor levels. Mice expressing high plasma levels of APC (APChigh) will be therefore crossed with Pros+/- mice to generate Pros+/--APChigh mice, which will be in turn intercrossed to generate Pros-/--APChigh mice. The viability and prothrombic phenotype of the latter mice will be investigated. Conditional Pros knockout mice will also allow us to specifically repress Pros expression in various tissues. Indeed, Pros is not only expressed in the liver but is expressed by endothelial cells, megakaryocytes and contained at high levels in circulating platelets. The contribution of platelet and endothelial Pros to thrombosis and inflammation will be investigated by crossing ProsLox/Lox mice to mice where Cre expression is under the control of platelet- and endothelium-specific promoter, respectively. In the longer run, generation of other tissue-specific Pros knockout mice will allow us to investigate the ability of Pros to function as a ligand of receptors tyrosine kinase of the Tyro3 family (TAM) in various cell types and biological processes.The second part of the project aims at a better understanding of the in vivo role of Gas6 and Pros pathways in platelet function in mice lacking Gas6 or any TAM receptors. In addition, as we found that the lack of one TAM receptor is responsible for a more severe phenotype than the lack of Gas6 itself, we hypothesize that a second ligand might be present in platelets. Pros is present in platelet ? granules from which it is secreted upon platelet activation. However, its role in platelet function is unknown. Therefore, we will study the role of Pros in platelet function. For this investigation, we have chosen to generate mice deficient in Pros only in platelets and study their platelet function in vitro and in vivo. If mice lacking Pros in their platelets have a platelet dysfunction, we will intercross them with Gas6 deficient mice or mice lacking Gas6 only in platelets to see if the platelet defect intensity correspond to that of mice lacking Gas6 alone or one or more of TAM receptors. We will also study the Gas6/Pros pathway in patients suffering from platelet dysfunction or thrombotic disorders.The third part of the project will be dedicated to the study of the role of Gas6/Pros pathway in inflammation in relationship with hemostasis. We found that Gas6, when secreted by monocytic cells in response to endotoxin dampens cytokine release from these cells. In sharp contrast, Gas6 deficient endothelial cells respond to TNF-? without increases in adhesion molecules and tissue factor exposure (the primary initiator of coagulation) and leukocytes transmigrate less extensively through them than through wild-type endothelial cells. Based on these observations, we will complete our studies on the role of Gas6 in inflammation by investigating the influence of Gas6/Pros pathway on coagulation parameters during endotoxemia and infection by using conditional tissue specific mice lacking Gas6, Pros, or one or more of the TAM receptors and by investigating Gas6/Pros pathway in the Lausanne sepsis cohort. Besides, we will further investigate another complication of inflammation involving Gas6, the anemia of chronic diseases and the potential role of Gas6/Pros in iron metabolism.In conclusion, our proposal aims at a better understanding of Gas6/Pros pathway in mechanisms of hemostasis, thrombosis and inflammation. Perspectives of this proposal include clinical trials implying Gas6 agonists or antagonists to treat human diseases such as bleeding disorders, thrombosis or sepsis.