Fluorescent nanoprobes as a biomarker for increased vascular permeability: implications in diagnosis and treatment of cancer and inflammation.

This article describes the use of a fluorescent nanoprobe as a functional biomarker for the identification of increased vascular permeability in cancer/arthritis disease models. Synthesis of the fluorescent nanoprobe was achieved by passive loading of a fluorophore inside the nanoparticle using thin film hydration method. The outer layer of the nanoprobe was decorated with poly(ethylene glycol) arms to increase the bioavailability of the fluorophore. Stability studies of the nanoprobe showed that the particles were stable up to 70 days. The uptake and internalization of the fluorescent nanoprobe inside target cells was confirmed by fluorescence microscopy studies. Co-localization of the probe with the target tissue in vivo was unambiguously identified using intravital microscopy. Results from in vivo imaging studies showed that the particles had a long half-life in the circulation and passively targeted tumor or arthritic tissue. The increased and specific uptake of the fluorescent nanoprobe in tumor/arthritic tissue is attributed to an enhanced permeation and retention (EPR) effect. Use of an optical method to validate anti-inflammatory drugs in an arthritis disease model is demonstrated in this study. In general, this methodology could be used for detection of leaky vasculature in different pathological states.

Spatial and temporal control of signaling through lipid rafts.

Sphingolipid- and cholesterol-dependent microdomains (rafts) order proteins at biological membranes and have been implicated in most signaling processes at the cell surface, but the principles and mechanisms through which lipid rafts influence signaling are not well understood. Recent studies have revealed how lipid rafts are rapidly redistributed and assembled locally in response to extracellular signals, and how components of raft-based signaling domains undergo rapid and regulated rearrangements influencing signal quality, duration, and strength. These findings highlight the exquisitely dynamic properties of signaling domains based on lipid rafts, and suggest that processes of raft trafficking and assembly take central roles in mediating spatial and temporal control of signaling.

Mlc1p promotes septum closure during cytokinesis via the IQ motifs of the vesicle motor Myo2p.

Little is known about the molecular machinery that directs secretory vesicles to the site of cell separation during cytokinesis. We show that in Saccharomyces cerevisiae, the class V myosin Myo2p and the Rab/Ypt Sec4p, that are required for vesicle polarization processes at all stages of the cell cycle, form a complex with each other and with a myosin light chain, Mlc1p, that is required for actomyosin ring assembly and cytokinesis. Mlc1p travels on secretory vesicles and forms a complex(es) with Myo2p and/or Sec4p. Its functional interaction with Myo2p is essential during cytokinesis to target secretory vesicles to fill the mother bud neck. The role of Mlc1p in actomyosin ring assembly instead is dispensable for this process. Therefore, in yeast, as recently shown in mammals, class V myosins associate with vesicles via the formation of a complex with Rab/Ypt proteins. Further more, myosin light chains, via their ability to be transported by secretory vesicles and to interact with class V myosin IQ motifs, can regulate vesicle polarization processes at a specific location and stage of the cell cycle.