Clinical overview of dalfampridine: an agent with a novel mechanism of action to help with gait disturbances.

Background: Medication used to treat multiple sclerosis (MS) can be categorized as disease-modifying therapies, symptomatic therapies, or treatment of acute exacerbations. Dalfampridine is the first symptomatic therapy approved by the Food and Drug Administration to improve walking in patients with MS.

Objective: This article reviews the pharmacology, pharmacodynamic properties, and pharmacokinetic properties of dalfampridine, as well as its clinical efficacy, safety profile, pharmacoeconomic considerations, and place in therapy.

Fusion between phagosomes, early and late endosomes: a role for actin in fusion between late, but not early endocytic organelles.

Actin is implicated in membrane fusion, but the precise mechanisms remain unclear. We showed earlier that membrane organelles catalyze the de novo assembly of F-actin that then facilitates the fusion between latex bead phagosomes and a mixture of early and late endocytic organelles. Here, we correlated the polymerization and organization of F-actin with phagosome and endocytic organelle fusion processes in vitro by using biochemistry and light and electron microscopy.

Internalization and stepwise degradation of heparan sulfate proteoglycans in rat hepatocytes.

Intracellular transport and degradation of membrane anchored heparan sulfate proteoglycans (HSPGs) were studied in cultured rat hepatocytes labeled with [35S]sulfate and [3H]glucosamine. Pulse chase experiments showed that membrane anchored HSPGs were constitutively transported to the cell surface after completion of polymerization and modification of the glycosaminoglycan chains in the Golgi apparatus. The intact HSPGs had a relatively short residence time at the cell surface and in non-degrading compartments (T(1/2) approximately 2-3 h), while [35S]sulfate labeled degradation products were found in lysosomes, and to a lesser extent in late endosomes.

ATP-dependent membrane assembly of F-actin facilitates membrane fusion.

We recently established an in vitro assay that monitors the fusion between latex-bead phagosomes and endocytic organelles in the presence of J774 macrophage cytosol (). Here, we show that different reagents affecting the actin cytoskeleton can either inhibit or stimulate this fusion process. Because the membranes of purified phagosomes can assemble F-actin de novo from pure actin with ATP (), we focused here on the ability of membranes to nucleate actin in the presence of J774 cytosolic extracts.

Actin assembly induced by polylysine beads or purified phagosomes: quantitation by a new flow cytometry assay.

Background: Actin assembly on biological membranes is a poorly understood process. We have previously shown that phagosomal membranes could induce actin assembly in the presence of thymosin beta4 (an actin sequestering protein that inhibits nonspecific nucleation), via the barbed ends of actin filaments.

Methods: Here, we have developed an in vitro system based on fluorescein-labeled G (monomeric) actin and flow cytometry analysis, which allowed us to quantify de novo actin assembly on the cytoplasmic side of purified phagosomes.