Summary:Circadian clocks are endogenous timers adjusting behaviour and physiology with the solar day 1 .Synchronized circadian clocks improve fitness 2 and are crucial for our physical and mental wellbeing 3 . Visual and non-visual photoreceptors are responsible for synchronizing circadian clocks to light 4,5 , but clock-resetting is also achieved by alternating day and night temperatures with only 2°-4°C difference [6][7][8] . This temperature sensitivity is remarkable considering that the circadian clock period (~24 h) is largely independent of surrounding ambient temperatures 1,8 .Here we show that Drosophila Ionotropic Receptor 25a (IR25a) is required for behavioural synchronization to low-amplitude temperature cycles. This channel is expressed in sensory neurons of internal stretch receptors previously implicated in temperature synchronization of the circadian clock 9 . IR25a is required for temperature-synchronized clock protein oscillations in subsets of central clock neurons. Extracellular leg nerve recordings reveal temperature -and IR25a-dependent sensory responses, and IR25a mis-expression confers temperature-dependent firing of heterologous neurons. We propose that IR25a is part of an input pathway to the circadian clock that detects small temperature differences. This pathway operates in the absence of known 'hot' and 'cold' sensors in the Drosophila antenna 10,11 , revealing the existence of novel periphery-to-brain temperature signalling channels. Main Text:In Drosophila, daily activity rhythms are controlled by a network of ~150 clock neurons expressing the clock genes period (per) and timeless (tim). These encode repressor proteins that 3 negatively feedback on their own promoters resulting in 24 h oscillations of clock molecules.Temperature cycles (TC) synchronise molecular clocks present in peripheral appendages in a tissue-autonomous manner 9,12 , while synchronization of clock neurons in the brain largely depends on peripheral temperature receptors located in the chordotonal organs (ChO) and the ChO-expressed gene nocte 9,12,13 .To discover novel factors involved in temperature entrainment, we identified NOCTEinteracting proteins by co-immunoprecipitation and mass-spectrometry (Extended Data Tab. 1) 14 . We focused on IR25a, a member of a divergent subfamily of ionotropic glutamate receptors and verified the interaction by co-immunoprecipitation after overexpressing IR25a and NOCTE in all clock cells using tim-gal4 (Extended Data Fig. 1a). IR25a is expressed in different populations of sensory neurons, including those in the antenna and labellum [15][16][17] . In the olfactory system IR25a acts as a co-receptor with different odour-sensing IRs 15 .To investigate if IR25a is co-expressed with nocte in ChO we analysed IR25a expression in femur and antennal ChO using an IR25a-gal4 line 15 (Extended Data Fig. 2a). IR25a-gal4 driven mCD8-GFP labelled subsets of ChO neurons in the femur, overlapping substantially with nompC-QF driven QUAS-Tomato signals (Fig. 1 a-c). nompC-QF is expressed in larv...

Although we now have a wealth of information on the transcription patterns of all the genes in the Drosophila genome, much less is known about the properties of the encoded proteins. To provide information on the expression patterns and subcellular localisations of many proteins in parallel, we have performed a large-scale protein trap screen using a hybrid piggyBac vector carrying an artificial exon encoding yellow fluorescent protein (YFP) and protein affinity tags. From screening 41 million embryos, we recovered 616 verified independent YFP-positive lines representing protein traps in 374 genes, two-thirds of which had not been tagged in previous P element protein trap screens. Over 20 different research groups then characterized the expression patterns of the tagged proteins in a variety of tissues and at several developmental stages. In parallel, we purified many of the tagged proteins from embryos using the affinity tags and identified co-purifying proteins by mass spectrometry. The fly stocks are publicly available through the Kyoto Drosophila Genetics Resource Center. All our data are available via an open access database (Flannotator), which provides comprehensive information on the expression patterns, subcellular localisations and in vivo interaction partners of the trapped proteins. Our resource substantially increases the number of available protein traps in Drosophila and identifies new markers for cellular organelles and structures.

Background: B cell receptor (BCR) clusters modulate BCR signaling in B-lymphocytes.Results: We used a quantitative proteomic proximity assay to analyze the BCR cluster in DT40 cells.Conclusion: Our proximity labeling assay identified novel components of the BCR cluster linked to integrin signaling.Significance: We provide new insights into BCR assembly and identify new and unexpected targets for further functional analysis.

Within cells, proteins can co-assemble into functionally integrated and spatially restricted multicomponent complexes. Often, the affinities between individual proteins are relatively weak, and proteins within such clusters may interact only indirectly with many of their other protein neighbors. This makes proteomic characterization difficult using methods such as immunoprecipitation or cross-linking. Recently, several groups have described the use of enzyme-catalyzed proximity labeling reagents that covalently tag the neighbors of a targeted protein with a small molecule such as fluorescein or biotin. The modified proteins can then be isolated by standard pulldown methods and identified by mass spectrometry. Here we will describe the techniques as well as their similarities and differences. We discuss their applications both to study protein assemblies and to provide a new way for characterizing organelle proteomes. We stress the importance of proteomic quantitation and independent target validation in such experiments. Furthermore, we suggest that there are biophysical and cell-biological principles that dictate the appropriateness of enzyme-catalyzed proximity labeling methods to address particular biological questions of interest.

Affinity purification coupled to mass spectrometry provides a reliable method for identifying proteins and their binding partners. In this study we have used Drosophila melanogaster proteins triple tagged with Flag, Strep II, and Yellow fluorescent protein in vivo within affinity pull-down experiments and isolated these proteins in their native complexes from embryos. We describe a pipeline for determining interactomes by Parallel Affinity Capture (iPAC) and show its use by identifying partners of several protein baits with a range of sizes and subcellular locations. This purification protocol employs the different tags in parallel and involves detailed comparison of resulting mass spectrometry data sets, ensuring the interaction lists achieved are of high confidence. We show that this approach identifies known interactors of bait proteins as well as novel interaction partners by comparing data achieved with published interaction data sets. The high confidence in vivo protein data sets presented here add new data to the currently incomplete D. melanogaster interactome. Additionally we report contaminant proteins that are persistent with affinity purifications irrespective of the tagged bait.

This manuscript describes a new and general method to identify proteins localized into spatially restricted membrane microenvironments. Horseradish peroxidase (HRP) is brought into contact with a target protein by being covalently linked to a primary or secondary antibody, an antigen or substrate, a drug, or a toxin. A biotinylated tyramide-based reagent is then added. In the presence of HRP and hydrogen peroxide, the reagent is converted into a free radical that only diffuses a short distance before covalently labeling proteins within a few tens to hundreds of nanometers from the target. The biotinylated proteins can then be isolated by standard affinity chromatography and identified by liquid chromatography (LC) and mass spectrometry (MS). The assay can be made quantitative by using stable isotope labeling with amino acids in cell culture (SILAC) or isobaric tagging at the peptide level.

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The growth of a range of Gram-positive bacteria was inhibited by organochlorine insecticides while that of Gram-negative organisms was unaffected. Growing cultures of Bacillus subtilis (ATCC 9372) treated with 20 p.p.m. technical chlordane ceased to grow and showed a decline in viable count and respiration rate, both being eliminated after about 3 h. A delayed release of incorporated ~-[U-l*C]leucine and L-malate dehydrogenase occurred concomitant with a fall of It is suggested that these phenomena are a result of disruption of membraneassociated metabolism, including electron transport and cell wall biosynthesis, which leads to cell lysis. No effect on these parameters occurred with growing cultures of Escherichia coli (ATCC 8739). The chlordane sensitivity of succinate oxidation by sphaeroplasts of E. coli indicates that the intact cell wall prevents penetration of pesticide to sensitive sites within the walls of Gram-negative bacteria.