Synthetic polyamines promote rapid lamellipodial growth by regulating actin dynamics.

Cellular protrusions involved in motile processes are driven by site-directed assembly of actin filaments in response to Rho-GTPase signalling. So far, only chemical compounds depolymerizing actin or stabilizing filaments, inhibiting N-WASP, Arp2/3 or formins, have been used to eliminate the formation of protrusions, while Rho-GTPase-dominant positive strategies have been designed to stimulate protrusions. Here we describe the design of four polyamines (macrocyclic and branched acyclic), and show that they enter the cell and induce specific growth of actin-enriched lamellipodia within minutes.

Intermittent depolymerization of actin filaments is caused by photo-induced dimerization of actin protomers.

Actin, one of the most abundant proteins within eukaryotic cells, assembles into long filaments that form intricate cytoskeletal networks and are continuously remodelled via cycles of actin polymerization and depolymerization. These cycles are driven by ATP hydrolysis, a process that also acts to destabilize the filaments as they grow older. Recently, abrupt dynamical changes during the depolymerization of single filaments have been observed and seemed to imply that old filaments are more stable than young ones [Kueh HY, et al.

Difference in lipid packing sensitivity of exchangeable apolipoproteins apoA-I and apoA-II: an important determinant for their distinctive role in lipid metabolism.

Exchangeable apolipoproteins A-I and A-II play distinct roles in reverse cholesterol transport. ApoA-I interacts with phospholipids and cholesterol of the cell membrane to make high density lipoprotein particles whereas apolipoprotein A-II interacts with high density lipoprotein particles to release apolipoprotein A-I. The two proteins show a high activity at the aqueous solution/lipid interface and are characterized by a high content of amphipathic α-helices built upon repetition of the same structural motif.

Fluid and condensed ApoA-I/phospholipid monolayers provide insights into ApoA-I membrane insertion.

Apolipoprotein A-I (ApoA-I) is a protein implicated in the solubilization of lipids and cholesterol from cellular membranes. The study of ApoA-I in phospholipid (PL) monolayers brings relevant information about ApoA-I/PL interactions. We investigated the influence of PL charge and acyl chain organization on the interaction with ApoA-I using dipalmitoyl-phosphatidylcholine, dioleoyl-phosphatidylcholine and dipalmitoyl-phosphatidylglycerol monolayers coupled to ellipsometric, surface pressure, atomic force microscopy and infrared (polarization modulation infrared reflection-absorption spectroscopy) measurements.