title: Activation induced morphological changes and integrin αIIbβ3 activity of living platelets.
abstract: Platelets are essential in hemostasis. Upon activation they undergo a shape-change accompanied with receptor presentation. Atomic force microscopy (AFM) imaging and single molecule force spectroscopy (SMFS) were used as powerful tools for exploring morphological changes as well as receptor activities of platelets. Imaging time series was accomplished with and without fixation steps at the single platelet level. Hereby the response of mechanical stimulation of the platelet by the AFM cantilever tip was directly observed. We demonstrate that living and fixed platelets develop filopodia after a short activation time followed by their disappearance including cellular bleb formation. Thereafter a second filopodia formation (filopodia extrusion) was observed; those filopodia subsequently disappeared again, and finally platelets detached from the support due to cell death. We determined the influence of mechanical stress on the chronology of morphological changes of platelets and demonstrated shear force induced filopodia formation. Through recordings over several hours, topographical AFM images over the full platelet lifetime - from early activation up to apoptosis - are presented. SMFS measurements on living platelets allowed determining the activation state of the most prominent membrane receptor integrin αIIbβ3 at all different phases of activation. αIIbβ3 was fully activated, independent of the morphological state.
authors.affiliation: Institute of Biophysics, University of Linz, Gruberstrasse 40, 4020 Linz, Austria.
authors.forename: Sandra
authors.initials: S
authors.lastname: Posch
authors.forename: Isabel
authors.initials: I
authors.lastname: Neundlinger
authors.forename: Michael
authors.initials: M
authors.lastname: Leitner
authors.forename: Peter
authors.initials: P
authors.lastname: Siostrzonek
authors.forename: Simon
authors.initials: S
authors.lastname: Panzer
authors.forename: Peter
authors.initials: P
authors.lastname: Hinterdorfer
authors.forename: Andreas
authors.initials: A
authors.lastname: Ebner
mesh_terms: D001696:Biomechanical Phenomena; D001792:Blood Platelets / Q000502:physiology* / Q000648:ultrastructure; D002448:Cell Adhesion; D048430:Cell Shape; D002478:Cells, Cultured; D006801:Humans; D018625:Microscopy, Atomic Force; D010973:Platelet Adhesiveness; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D011485:Protein Binding; D011554:Pseudopodia / Q000648:ultrastructure; D013312:Stress, Physiological
chemical_list: D019039:Platelet Glycoprotein GPIIb-IIIa Complex