title: Actin is not required for nanotubular protrusions of primary astrocytes grown on metal nano-lawn.
abstract: We used sub-micron metal rod decorated surfaces, 'nano-lawn' structures, as a substrate to study cell-to-cell and cell-to-surface interactions of primary murine astrocytes. These cells form thin membranous tubes with diameters of less than 100 nm and a length of several microns, which make contact to neighboring cells and the substrate during differentiation. While membrane protrusions grow on top of the nano-lawn pillars, nuclei sink to the bottom of the substrate. We observed gondola-like structures along those tubes, suggestive of their function as transport vehicles. Elements of the cytoskeleton such as actin fibers are commonly believed to be essential for triggering the onset and growth of tubular membrane protrusions. A rope-pulling mechanism along actin fibers has recently been proposed to account for the transport or exchange of cellular material between cells. We present evidence for a complementary mechanism that promotes growth and stabilization of the observed tubular protrusions of cell membranes. This mechanism does not require active involvement of actin fibers as the formation of membrane protrusions could not be prevented by suppressing polymerization of actin by latrunculin B. Also theoretically, actin fibers are not essential for the growing and stability of nanotubes since curvature-driven self-assembly of interacting anisotropic raft elements is sufficient for the spontaneous formation of thin nano-tubular membrane protrusions.
authors.affiliation: Research Institute for the Biology of Farm Animals, Research Unit Behavioural Physiology, Dummerstorf, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Gimsa
authors.forename: Ales
authors.initials: A
authors.lastname: Iglic
authors.forename: Stefan
authors.initials: S
authors.lastname: Fiedler
authors.forename: Michael
authors.initials: M
authors.lastname: Zwanzig
authors.forename: Veronika
authors.initials: V
authors.lastname: Kralj-Iglic
authors.forename: Ludwig
authors.initials: L
authors.lastname: Jonas
authors.forename: Jan
authors.initials: J
authors.lastname: Gimsa
mesh_terms: D051339:Actin Depolymerizing Factors / Q000494:pharmacology; D000199:Actins / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000000981:diagnostic imaging* / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000648:ultrastructure*; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D022081:Cell Surface Extensions / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D002478:Cells, Cultured; D006046:Gold / Q000737:chemistry; D021962:Membrane Microdomains / Q000502:physiology* / Q000648:ultrastructure; D051379:Mice; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D043942:Nanotubes / Q000737:chemistry / Q000648:ultrastructure*; D010984:Platinum / Q000737:chemistry; D013499:Surface Properties; D053778:Thiazolidines / Q000494:pharmacology; D014463:Ultrasonography
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D053778:Thiazolidines; D010984:Platinum; D006046:Gold; C037067:latrunculin A