title: Mechanics of spreading cells probed by atomic force microscopy.
abstract: Cellular adhesion and motility are fundamental processes in biological systems such as morphogenesis and tissue homeostasis. During these processes, cells heavily rely on the ability to deform and supply plasma membrane from pre-existing membrane reservoirs, allowing the cell to cope with substantial morphological changes. While morphological changes during single cell adhesion and spreading are well characterized, the accompanying alterations in cellular mechanics are scarcely addressed. Using the atomic force microscope, we measured changes in cortical and plasma membrane mechanics during the transition from early adhesion to a fully spread cell. During the initial adhesion step, we found that tremendous changes occur in cortical and membrane tension as well as in membrane area. Monitoring the spreading progress by means of force measurements over 2.5 h reveals that cortical and membrane tension become constant at the expense of excess membrane area. This was confirmed by fluorescence microscopy, which shows a rougher plasma membrane of cells in suspension compared with spread ones, allowing the cell to draw excess membrane from reservoirs such as invaginations or protrusions while attaching to the substrate and forming a first contact zone. Concretely, we found that cell spreading is initiated by a transient drop in tension, which is compensated by a decrease in excess area. Finally, all mechanical parameters become almost constant although morphological changes continue. Our study shows how a single cell responds to alterations in membrane tension by adjusting its overall membrane area. Interference with cytoskeletal integrity, membrane tension and excess surface area by administration of corresponding small molecular inhibitors leads to perturbations of the spreading process.
authors.affiliation: Institute of Physical Chemistry, Georg-August-University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Pietuch
authors.forename: Andreas
authors.initials: A
authors.lastname: Janshoff
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D015638:Cytochalasin D / Q000737:chemistry / Q000494:pharmacology; D004285:Dogs; D004548:Elasticity; D005456:Fluorescent Dyes / Q000737:chemistry; D006834:Hydrazines / Q000737:chemistry; D061985:Madin Darby Canine Kidney Cells; D018625:Microscopy, Atomic Force; D008954:Models, Biological
chemical_list: C417561:Alexa 488 hydrazide; D005456:Fluorescent Dyes; D006834:Hydrazines; D015638:Cytochalasin D
keywords: adhesion; cell mechanics; membrane tension; spreading