title: PAR1 signaling regulates the retention and recruitment of EPCR-expressing bone marrow hematopoietic stem cells.
abstract: Retention of long-term repopulating hematopoietic stem cells (LT-HSCs) in the bone marrow is essential for hematopoiesis and for protection from myelotoxic injury. We report that signaling cascades that are traditionally viewed as coagulation related also control retention of endothelial protein C receptor-positive (EPCR(+)) LT-HSCs in the bone marrow and their recruitment to the blood via two pathways mediated by protease activated receptor 1 (PAR1). Thrombin-PAR1 signaling induces nitric oxide (NO) production, leading to EPCR shedding mediated by tumor necrosis factor-α-converting enzyme (TACE), enhanced CXCL12-CXCR4-induced motility and rapid stem and progenitor cell mobilization. Conversely, bone marrow blood vessels provide a microenvironment enriched with activated protein C (aPC) that retains EPCR(+) LT-HSCs by limiting NO generation, reducing Cdc42 activity and enhancing integrin VLA4 affinity and adhesion. Inhibition of NO production by aPC-EPCR-PAR1 signaling reduces progenitor cell egress from the bone marrow, increases retention of bone marrow NO(low) EPCR(+) LT-HSCs and protects mice from chemotherapy-induced hematological failure and death. Our study reveals new roles for PAR1 and EPCR in controlling NO production to balance maintenance and recruitment of bone marrow EPCR(+) LT-HSCs, with potential clinical relevance for stem cell transplantation.
authors.affiliation: Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Shiri
authors.initials: S
authors.lastname: Gur-Cohen
authors.affiliation: Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Tomer
authors.initials: T
authors.lastname: Itkin
authors.affiliation: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, USA.
authors.forename: Sagarika
authors.initials: S
authors.lastname: Chakrabarty
authors.affiliation: Center for Thrombosis and Hemostasis, Johannes Gutenberg-University Medical Center, Mainz, Germany.
authors.forename: Claudine
authors.initials: C
authors.lastname: Graf
authors.affiliation: Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Orit
authors.initials: O
authors.lastname: Kollet
authors.affiliation: Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Aya
authors.initials: A
authors.lastname: Ludin
authors.affiliation: Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Karin
authors.initials: K
authors.lastname: Golan
authors.affiliation: Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kalinkovich
authors.affiliation: Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.|Internal Medicine Department T, Tel-Aviv Sourasky Medical Center, Tel-Aviv, Israel.
authors.forename: Guy
authors.initials: G
authors.lastname: Ledergor
authors.affiliation: Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Eitan
authors.initials: E
authors.lastname: Wong
authors.affiliation: Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.|Universitätsklinikum Schleswig-Holstein Campus Luebeck, Klinik für Strahlentherapie, Universitaet zu Luebeck, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Niemeyer
authors.affiliation: Flow Cytometry Unit, Department of Biological Services, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Ziv
authors.initials: Z
authors.lastname: Porat
authors.affiliation: Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Ayelet
authors.initials: A
authors.lastname: Erez
authors.affiliation: Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Irit
authors.initials: I
authors.lastname: Sagi
authors.affiliation: Coagulation Biology Laboratory, Oklahoma Medical Research Foundation and Departments of Pathology and Biochemistry &Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.
authors.forename: Charles T
authors.initials: CT
authors.lastname: Esmon
authors.affiliation: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, USA.|Center for Thrombosis and Hemostasis, Johannes Gutenberg-University Medical Center, Mainz, Germany.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Ruf
authors.affiliation: Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Tsvee
authors.initials: T
authors.lastname: Lapidot
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism; D000072198:ADAM17 Protein; D000818:Animals; D001853:Bone Marrow / Q000378:metabolism; D002448:Cell Adhesion; D002465:Cell Movement; D054377:Chemokine CXCL12 / Q000378:metabolism; D000074283:Endothelial Protein C Receptor; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D039041:Integrin alpha4beta1 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000378:metabolism*; D011486:Protein C / Q000378:metabolism*; D044463:Receptor, PAR-1 / Q000378:metabolism*; D019718:Receptors, CXCR4 / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D015398:Signal Transduction; D013917:Thrombin / Q000378:metabolism*; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism
chemical_list: C514936:CXCR4 protein, mouse; C581598:Cdc42 protein, mouse; D054377:Chemokine CXCL12; C515256:Cxcl12 protein, mouse; D000074283:Endothelial Protein C Receptor; D039041:Integrin alpha4beta1; C080248:Procr protein, mouse; D011486:Protein C; D044463:Receptor, PAR-1; D019718:Receptors, CXCR4; D011956:Receptors, Cell Surface; D009569:Nitric Oxide; D013917:Thrombin; D051722:ADAM Proteins; D000072198:ADAM17 Protein; C000606463:Adam17 protein, mouse; D020764:cdc42 GTP-Binding Protein