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Intracellular trafficking governs receptor signaling, pathogenesis, immune responses and fate of nanomedicines. These processes are typically tracked by observing colocalization of fluorescent markers using confocal microscopy. However, this method is low throughput, limited by the resolution of microscopy, and can miss fleeting interactions. To address this, we developed a localization sensor composed of a quenched SNAP-tag substrate (SNAPSwitch) that can be conjugated to biomolecules using click chemistry. SNAPSwitch enables quantitative detection of trafficking to locations of interest within live cells using flow cytometry. Using SNAPSwitch, we followed the trafficking of DNA complexes from endosomes into the cytosol and nucleus. We show that antibodies against the transferrin or hyaluronan receptor are initially sorted into different compartments following endocytosis. In addition, we can resolve which side of the cellular membrane material was located. These results demonstrate SNAPSwitch is a high-throughput and broadly applicable tool to quantitatively track localization of materials in cells., Determining the trafficking of intracellular material is commonly done by colocalisation analysis using microscopy. Here the authors monitor trafficking of select cargo by measuring the conversion of quenched SNAP-tag substrates by subcellularly-localised SNAP-tag and detection by flow cytometry.

Neutrophil elastase is a serine protease that has been implicated in the pathogenesis of inflammatory bowel disease. Due to post-translational control of its activation and high expression of its inhibitors in the gut, measurements of total expression poorly reflect the pool of active, functional neutrophil elastase. Fluorogenic substrate probes have been used to measure neutrophil elastase activity, though these tools lack specificity and traceability. PK105 is a recently described fluorescent activity-based probe, which binds to neutrophil elastase in an activity-dependent manner. The irreversible nature of this probe allows for accurate identification of its targets in complex protein mixtures. We describe the reactivity profile of PK105b, a new analogue of PK105, against recombinant serine proteases and in tissue extracts from healthy mice and from models of inflammation induced by oral cancer and Legionella pneumophila infection. We apply PK105b to measure neutrophil elastase activation in an acute model of experimental colitis. Neutrophil elastase activity is detected in inflamed, but not healthy, colons. We corroborate this finding in mucosal biopsies from patients with ulcerative colitis. Thus, PK105b facilitates detection of neutrophil elastase activity in tissue lysates, and we have applied it to demonstrate that this protease is unequivocally activated during colitis.

Pseudocontact shifts (PCS) induced by tags loaded with paramagnetic lanthanide ions provide powerful long-range structure information, provided the location of the metal ion relative to the target protein is known. Usually, the metal position is determined by fitting the magnetic susceptibility anisotropy (Δχ) tensor to the 3D structure of the protein in an 8-parameter fit, which requires a large set of PCSs to be reliable. In an alternative approach, we used multiple Gd(3+)-Gd(3+) distances measured by double electron-electron resonance (DEER) experiments to define the metal position, allowing Δχ-tensor determinations from more robust 5-parameter fits that can be performed with a relatively sparse set of PCSs. Using this approach with the 32 kDa E. coli aspartate/glutamate binding protein (DEBP), we demonstrate a structural transition between substrate-bound and substrate-free DEBP, supported by PCSs generated by C3-Tm(3+) and C3-Tb(3+) tags attached to a genetically encoded p-azidophenylalanine residue. The significance of small PCSs was magnified by considering the difference between the chemical shifts measured with Tb(3+) and Tm(3+) rather than involving a diamagnetic reference. The integrative sparse data approach developed in this work makes poorly soluble proteins of limited stability amenable to structural studies in solution, without having to rely on cysteine mutations for tag attachment.

Intrathecal baclofen (ITB) therapy for spasticity has been suggested to accelerate the development of scoliosis. We present the case of a 17-year-old female patient with cerebral palsy who had ITB therapy from the age of 11 years. During this period, she developed a severe scoliosis measuring 86° from T11 to L4, with pain due to costo-pelvic impingement. Her baclofen pump had reached its end of life and required replacement if ITB therapy was to continue. This coincided with plans for scoliosis corrective surgery. METHODS: We performed scoliosis correction along with removal of baclofen pump and selective dorsal rhizotomy (SDR), as a single combined procedure. SDR was performed instead of ITB pump replacement for management of spasticity. RESULTS: Following surgery, scoliosis improved to 24°. At 6 month follow-up, there was significant improvement in spasticity and quality of life. CONCLUSIONS: This report illustrates the feasibility of a combined procedure to correct scoliosis and manage spasticity with SDR. We present the case details, our management and review of the published literature regarding the factors influencing treatment of scoliosis and spasticity.