Shedding light on Toll signaling through live imaging

The Toll receptor propagates the ventralizing signal designating dorsal/ventral cell fate in the Drosophila embryo. The application of live-imaging approaches to this classical developmental signaling pathway is yielding some surprising new insights into Toll receptor signaling. In addition to its previously known plasma membrane localization, Toll is present in Rab5+ early endosomes. Dominant, constitutively active forms of Toll preferentially partition into endosomes. Blocking endocytosis locally prevents Toll from signaling suggesting that endocytosis is required for Toll to signal. Augmenting endocytosis increases Toll signaling. Both interventions alter the shape of the Dorsal gradient globally indicating an important role of endocytosis in fixing spatial information for the Dorsal gradient.     

Shedding light on current trends in molecular optogenetics

Molecular optogenetics is a highly dynamic research field. In the past two years, the field was characterized by the development of new allosteric switches as well as the forward integration of optogenetics research towards application. Further, two areas of research have significantly gathered momentum, the use of optogenetics to control liquid–liquid phase separation as well as the application of optogenetic tools in the extracellular space. Here, we review these areas and discuss future directions.     

Shedding light on health and disease using molecular beacons.

The detection and identification of pathogens is often painstaking due to the low abundance of diseased cells in clinical samples. The genomic sequences of the pathogen can be amplified through methods such as the polymerase chain reaction and nucleic acid sequence-based amplification, but the nucleic acid targets are often lost among other unintended products of amplification. Novel nucleic acid probes known as molecular beacons have been developed allowing for the rapid and specific detection of genetic markers of a disease. Molecular beacons are hairpin-forming oligonucleotides labelled at one end with a quencher and at the other end with a fluorescent reporter dye. In the absence of target, the fluorescence is quenched. In the presence of target, the hairpin structure opens upon beacon/target hybridisation, resulting in the restoration of fluorescence. The ability to transduce target recognition into a fluorescence signal with high signal-to-background ratio, coupled with an improved specificity, has allowed molecular beacons to enjoy a wide range of biological and biomedical applications. Here, we describe the basic features of molecular beacons, review their applications in disease detection and diagnosis and discuss some of the issues and challenges of in vivo studies. The aim of this paper is to foster the development of new molecular beacon-based assays and to stimulate the application of this technology in laboratory and clinical studies of health and disease.     

Shedding light on melanoma

Not just confined to sunny places, the incidence of melanoma has been rising in all fair-skinned populations around the world. How much is known about the causes of this disease, and can this knowledge be applied to preventive strategies?     

Shedding a little light on light chains

Myosin II regulatory light chains have an important role in the organization and function of the contractile machinery at cytokinesis. Two recent reports provide new insights into these important proteins.     

Shedding light on ADAM metalloproteinases

ADAM metalloproteinase disintegrins have emerged as the major proteinase family that mediates ectodomain shedding, the proteolytic release of extracellular domains from their membrane-bound precursors. Recent gene-manipulation studies have established the role of ADAM-mediated shedding in mammalian physiology and, in addition, raised the issue of functional redundancy among ADAM sheddases. ADAM sheddases activate, for example, growth factors and cytokines, thus regulating signalling pathways that are important in development and pathological processes such as cancer. The recent studies have also begun to elucidate the substrate specificity and the mechanisms that control ADAM-mediated shedding events that regulate, for example, growth-factor and Notch signalling, and the processing of the amyloid precursor protein.     

Shedding light on Merlin's wizardry

Inactivation of the tumor suppressor Merlin, encoded by the NF2 (Neurofibromatosis type 2) gene, contributes to malignant conversion in many cell types. Merlin is an Ezrin-Radixin-Moesin protein and localizes underneath the plasma membrane at cell-cell junctions and other actin-rich sites. Recent studies indicate that Merlin mediates contact inhibition of proliferation by blocking recruitment of Rac to the plasma membrane. In mitogen-stimulated cells, p21-activated kinase phosphorylates Ser518 in the C-terminus of Merlin, inactivating the growth suppressive function of the protein. Furthermore, the myosin phosphatase MYPT1-PP1delta, has been identified as a direct activator of Merlin and its inhibition has been linked to malignant transformation. Finally, studies in the fruit fly Drosophila melanogaster have revealed that Merlin functions together with the band 4.1 protein Expanded to promote [corrected] the endocytosis of many signaling receptors, limiting [corrected] their accumulation at the plasma membrane, and to activate [corrected] the Hippo signaling pathway. Here, we review these recent findings and their relevance to the tumor suppressor function of Merlin.     

Shedding light on prion disease

Several fatal, progressive neurodegenerative diseases, including various prion and prion-like disorders, are connected with the misfolding of specific proteins. These proteins misfold into toxic oligomeric species and a spectrum of distinct self-templating amyloid structures, termed strains. Hence, small molecules that prevent or reverse these protein-misfolding events might have therapeutic utility. Yet it is unclear whether a single small molecule can antagonize the complete repertoire of misfolded forms encompassing diverse amyloid polymorphs and soluble oligomers. We have begun to investigate this issue using the yeast prion protein, Sup35, as an experimental paradigm. We have discovered that a polyphenol, (-)epigallocatechin-3-gallate (EGCG), effectively inhibited the formation of infectious amyloid forms (prions) of Sup35 and even remodeled preassembled prions. Surprisingly, EGCG selectively modulated specific prion strains and even selected for EGCG-resistant prion strains with novel structural and biological characteristics. Thus, treatment with a single small molecule antagonist of amyloidogenesis can select for novel, drug-resistant amyloid polymorphs. Importantly, combining EGCG with another small molecule, 4,5-bis-(4-methoxyanilino)phthalimide, synergistically antagonized and remodeled a wide array of Sup35 prion strains without producing any drug-resistant prions. We suggest that minimal drug cocktails, small collections of drugs that collectively antagonize all amyloid polymorphs, should be identified to besiege various neurodegenerative disorders.     

Shedding light on Salmonella carriers

Host-to-host transmission in most Salmonella serovars occurs primarily via the fecal-oral route. Salmonella enterica serovar Typhi is a human host-adapted pathogen and some S. Typhi patients become asymptomatic carriers. These individuals excrete large numbers of the bacteria in their feces and transmit the pathogen by contaminating water or food sources. The carrier state has also been described in livestock animals and is responsible for food-borne epidemics. Identification and treatment of carriers are crucial for the control of disease outbreaks. In this review, we describe recent advances in molecular profiling of human carriers and the use of animal models to identify potential host and bacterial genes involved in the establishment of the carrier state.