title: Platelet geometry sensing spatially regulates α-granule secretion to enable matrix self-deposition.
abstract: Although the biology of platelet adhesion on subendothelial matrix after vascular injury is well characterized, how the matrix biophysical properties affect platelet physiology is unknown. Here we demonstrate that geometric orientation of the matrix itself regulates platelet α-granule secretion, a key component of platelet activation. Using protein microcontact printing, we show that platelets spread beyond the geometric constraints of fibrinogen or collagen micropatterns with <5-µm features. Interestingly, α-granule exocytosis and deposition of the α-granule contents such as fibrinogen and fibronectin were primarily observed in those areas of platelet extension beyond the matrix protein micropatterns. This enables platelets to "self-deposit" additional matrix, provide more cellular membrane to extend spreading, and reinforce platelet-platelet connections. Mechanistically, this phenomenon is mediated by actin polymerization, Rac1 activation, and αIIbβ3 integrin redistribution and activation, and is attenuated in gray platelet syndrome platelets, which lack α-granules, and Wiskott-Aldrich syndrome platelets, which have cytoskeletal defects. Overall, these studies demonstrate how platelets transduce geometric cues of the underlying matrix geometry into intracellular signals to extend spreading, which endows platelets spatial flexibility when spreading onto small sites of exposed subendothelium.
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA; Aflac Cancer Center and Blood Disorders Service of Children's Healthcare of Atlanta, Atlanta, GA; Department of Pediatrics, Emory University School of Medicine, Atlanta, GA; Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA; Winship Cancer Institute, Emory University, Atlanta, GA; Institute of Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA;
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Sakurai
authors.affiliation: Division of Hemostasis and Thrombosis, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA; and.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Fitch-Tewfik
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA; Aflac Cancer Center and Blood Disorders Service of Children's Healthcare of Atlanta, Atlanta, GA; Department of Pediatrics, Emory University School of Medicine, Atlanta, GA; Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA; Winship Cancer Institute, Emory University, Atlanta, GA; Institute of Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA;
authors.forename: Yongzhi
authors.initials: Y
authors.lastname: Qiu
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA; Aflac Cancer Center and Blood Disorders Service of Children's Healthcare of Atlanta, Atlanta, GA; Department of Pediatrics, Emory University School of Medicine, Atlanta, GA; Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA; Winship Cancer Institute, Emory University, Atlanta, GA; Institute of Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA;
authors.forename: Byungwook
authors.initials: B
authors.lastname: Ahn
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA; Aflac Cancer Center and Blood Disorders Service of Children's Healthcare of Atlanta, Atlanta, GA; Department of Pediatrics, Emory University School of Medicine, Atlanta, GA; Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA; Winship Cancer Institute, Emory University, Atlanta, GA; Institute of Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA;
authors.forename: David R
authors.initials: DR
authors.lastname: Myers
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA; Aflac Cancer Center and Blood Disorders Service of Children's Healthcare of Atlanta, Atlanta, GA; Department of Pediatrics, Emory University School of Medicine, Atlanta, GA; Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA; Winship Cancer Institute, Emory University, Atlanta, GA; Institute of Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA;
authors.forename: Reginald
authors.initials: R
authors.lastname: Tran
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA; Aflac Cancer Center and Blood Disorders Service of Children's Healthcare of Atlanta, Atlanta, GA; Department of Pediatrics, Emory University School of Medicine, Atlanta, GA; Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA; Winship Cancer Institute, Emory University, Atlanta, GA; Institute of Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA;
authors.forename: Meredith E
authors.initials: ME
authors.lastname: Fay
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, GA;
authors.forename: Lingmei
authors.initials: L
authors.lastname: Ding
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, GA;
authors.forename: Paul W
authors.initials: PW
authors.lastname: Spearman
authors.affiliation: Center for Platelet Research Studies, Division of Hematology/Oncology, Boston Children's Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA.
authors.forename: Alan D
authors.initials: AD
authors.lastname: Michelson
authors.affiliation: Division of Hemostasis and Thrombosis, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA; and.
authors.forename: Robert
authors.initials: R
authors.lastname: Flaumenhaft
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA; Aflac Cancer Center and Blood Disorders Service of Children's Healthcare of Atlanta, Atlanta, GA; Department of Pediatrics, Emory University School of Medicine, Atlanta, GA; Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA; Winship Cancer Institute, Emory University, Atlanta, GA; Institute of Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA;
authors.forename: Wilbur A
authors.initials: WA
authors.lastname: Lam
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D001792:Blood Platelets / Q000166:cytology* / Q000378:metabolism*; D016022:Case-Control Studies; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D005089:Exocytosis / Q000502:physiology*; D005340:Fibrinogen / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D055652:Gray Platelet Syndrome / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007124:Immunoenzyme Techniques; D015539:Platelet Activation; D010973:Platelet Adhesiveness / Q000502:physiology*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D011554:Pseudopodia; D014923:Wiskott-Aldrich Syndrome / Q000378:metabolism / Q000473:pathology*
chemical_list: D005353:Fibronectins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D005340:Fibrinogen