title: Direct Cytoskeleton Forces Cause Membrane Softening in Red Blood Cells.
abstract: Erythrocytes are flexible cells specialized in the systemic transport of oxygen in vertebrates. This physiological function is connected to their outstanding ability to deform in passing through narrow capillaries. In recent years, there has been an influx of experimental evidence of enhanced cell-shape fluctuations related to metabolically driven activity of the erythroid membrane skeleton. However, no direct observation of the active cytoskeleton forces has yet been reported to our knowledge. Here, we show experimental evidence of the presence of temporally correlated forces superposed over the thermal fluctuations of the erythrocyte membrane. These forces are ATP-dependent and drive enhanced flickering motions in human erythrocytes. Theoretical analyses provide support for a direct force exerted on the membrane by the cytoskeleton nodes as pulses of well-defined average duration. In addition, such metabolically regulated active forces cause global membrane softening, a mechanical attribute related to the functional erythroid deformability.
authors.affiliation: Department of Physical Chemistry, Universidad Complutense. Ciudad Universitaria, Madrid, Spain.
authors.forename: Ruddi
authors.initials: R
authors.lastname: Rodríguez-García
authors.affiliation: Department of Physical Chemistry, Universidad Complutense. Ciudad Universitaria, Madrid, Spain; Instituto de Investigación Hospital Doce de Octubre (i+12), Madrid, Spain.
authors.forename: Iván
authors.initials: I
authors.lastname: López-Montero
authors.affiliation: Department of Physical Chemistry, Universidad Complutense. Ciudad Universitaria, Madrid, Spain; Instituto de Investigación Hospital Doce de Octubre (i+12), Madrid, Spain.
authors.forename: Michael
authors.initials: M
authors.lastname: Mell
authors.affiliation: Departament of Cell Biology, Immunology and Neurosciences, University of Barcelona School of Medicine and Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Nanociències i Nanotecnologia (IN(2)UB), Barcelona, Spain.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Egea
authors.affiliation: Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Nir S
authors.initials: NS
authors.lastname: Gov
authors.affiliation: Department of Physical Chemistry, Universidad Complutense. Ciudad Universitaria, Madrid, Spain; Instituto de Investigación Hospital Doce de Octubre (i+12), Madrid, Spain. Electronic address: monroy@ucm.es.
authors.forename: Francisco
authors.initials: F
authors.lastname: Monroy
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001696:Biomechanical Phenomena; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D013314:Stress, Mechanical
chemical_list: D000255:Adenosine Triphosphate