ABSTRACT
Filopodia, dynamic membrane protrusions driven by polymerization of an actin filament core, can adhere to the extracellular matrix and experience both external and cell-generated pulling forces. The role of such forces in filopodia adhesion is however insufficiently understood. Here, we study filopodia induced by overexpression of myosin X, typical for cancer cells. The lifetime of such filopodia positively correlates with the presence of myosin IIA filaments at the filopodia bases. Application of pulling forces to the filopodia tips through attached fibronectin-coated laser-trapped beads results in sustained growth of the filopodia. Pharmacological inhibition or knockdown of myosin IIA abolishes the filopodia adhesion to the beads. Formin inhibitor SMIFH2, which causes detachment of actin filaments from formin molecules, produces similar effect. Thus, centripetal force generated by myosin IIA filaments at the base of filopodium and transmitted to the tip through actin core in a formin-dependent fashion is required for filopodia adhesion.
Subject(s)
Formins/metabolism , Myosins/metabolism , Neoplasms/metabolism , Nonmuscle Myosin Type IIA/metabolism , Pseudopodia/physiology , Actin Cytoskeleton , Animals , COS Cells , Chlorocebus aethiops , Formins/antagonists & inhibitors , Formins/genetics , Formins/ultrastructure , Gene Expression Regulation, Neoplastic , HeLa Cells , Humans , Microfilament Proteins , Nonmuscle Myosin Type IIA/antagonists & inhibitors , Nonmuscle Myosin Type IIA/genetics , Nonmuscle Myosin Type IIA/ultrastructure , Pseudopodia/pathology , Thiones/pharmacology , Uracil/analogs & derivatives , Uracil/pharmacologyABSTRACT
We present here oil-in-water microemulsions stabilized by charged diblock copolymers alone, along with their structural characterization by small-angle neutron scattering measurements. They consist of swollen spherical micelles containing small amounts of oil in their core, which is surrounded by a corona of stretched polyelectrolyte chains. Structural changes, including core size variations, are evidenced when using a cosurfactant, or upon addition of salt, through a contraction of the charged corona. Attempts to relate the micellar structure to the individual copolymer characteristics are also presented, and show that the size of the hydrophobic block mainly determines that of the micelles.
ABSTRACT
We have performed neutron reflectivity measurements on a monolayer of charged diblock copolymers in a Langmuir trough, and determined precise density profiles of the polyelectrolyte brush at different densities. We obtain profiles in good agreement with existing self-consistent field computations, both for the osmotic and the salted brush regime. We show that the osmotic brush's thickness increases with density.
