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1. Increased PD ‐L1 expression in breast and colon cancer stem cells

   https://doi.org/10.1111/1440-1681.12732  

   Wu, Yanheng ; Chen, Mingshui ; Wu, Peihong ; Chen, Chen ; Xu, Zhi Ping ; Gu, Wenyi ( April 2017 , Clinical and Experimental Pharmacology and Physiology)

   Here we report the expression of programmed cell death ligand 1/2 (PD‐L1/L2) in breast and colon cancer stem cells (CSCs). The stemness of these cells was confirmed by their surface markers. Using flow cytometry analysis we demonstrated thatPD‐L1 expression was higher inCSCs of both cancers compared to non‐stem like cancer cells. Consistent with this, detection of cellularPD‐L1 proteins by western blot assay also showed increasedPD‐L1 protein inCSCs. In contrast, only trace amounts ofPD‐L2 were detected inCSCs of both cancers. Our results suggest that breast and colon cancers may be sensitive toPD1/PD‐L1 immunotherapy and thus warrant further investigations ofCSCtargetedPD1/PD‐L1 therapy.

    

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2. In vivo localization of iron starvation induced proteins under variable iron supplementation regimes in Phaeodactylum tricornutum

   https://doi.org/10.1002/pld3.472  

   Kazamia, Elena ; Mach, Jan ; McQuaid, Jeffrey B. ; Gao, Xia ; Coale, Tyler H. ; Malych, Ronald ; Camadro, Jean‐Michel ; Lesuisse, Emmanuel ; Allen, Andrew E. ; Bowler, Chris ; et al ( December 2022 , Plant Direct)

   The model pennate diatomPhaeodactylum tricornutumis able to assimilate a range of iron sources. It therefore provides a platform to study different mechanisms of iron processing concomitantly in the same cell. In this study, we follow the localization of three iron starvation induced proteins (ISIPs) in vivo, driven by their native promoters and tagged by fluorophores in an engineered line ofP. tricornutum. We find that the localization patterns of ISIPs are dynamic and variable depending on the overall iron status of the cell and the source of iron it is exposed to. Notwithstanding, a shared destination of the three ISIPs both under ferric iron and siderophore‐bound iron supplementation is a globular compartment in the vicinity of the chloroplast. In a proteomic analysis, we identify that the cell engages endocytosis machinery involved in the vesicular trafficking as a response to siderophore molecules, even when these are not bound to iron. Our results suggest that there may be a direct vesicle traffic connection between the diatom cell membrane and the periplastidial compartment (PPC) that co‐opts clathrin‐mediated endocytosis and the “cytoplasm to vacuole” (Cvt) pathway, for proteins involved in iron assimilation.

   Proteomics data are available via ProteomeXchange with identifier PXD021172.

   The marine diatomP. tricornutumengages a vesicular network to traffic siderophores and phytotransferrin from the cell membrane directly to a putative iron processing site in the vicinity of the chloroplast.

    

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3. Molecular and electrophysiological characterization of anion transport in Arabidopsis thaliana pollen reveals regulatory roles for pH , Ca 2+ and GABA

   https://doi.org/10.1111/nph.15863  

   Domingos, Patrícia ; Dias, Pedro N. ; Tavares, Bárbara ; Portes, Maria Teresa ; Wudick, Michael M. ; Konrad, Kai R. ; Gilliham, Matthew ; Bicho, Ana ; Feijó, José A. ( May 2019 , New Phytologist)

   We investigated the molecular basis and physiological implications of anion transport during pollen tube (PT) growth inArabidopsis thaliana(Col‐0).

   Patch‐clamp whole‐cell configuration analysis of pollen grain protoplasts revealed three subpopulations of anionic currents differentially regulated by cytoplasmic calcium ([Ca²⁺]_cyt). We investigated the pollen‐expressed proteinsAtSLAH3,AtALMT12,AtTMEM16 andAtCCCas the putative anion transporters responsible for these currents.

   AtCCC‐GFPwas observed at the shank andAtSLAH3‐GFPat the tip and shank of thePTplasma membrane. Both are likely to carry the majority of anion current at negative potentials, as extracellular anionic fluxes measured at the tip ofPTs with an anion vibrating probe were significantly lower inslah3^−/−andccc^−/−mutants, but unaffected inalmt12^−/−andtmem16^−/−. We further characterised the effect ofpHandGABAby patch clamp. Strong regulation by extracellularpHwas observed in the wild‐type, but not intmem16^−/−. Our results are compatible withAtTMEM16 functioning as an anion/H⁺cotransporter and therefore, as a putativepHsensor.GABApresence: (1) inhibited the overall currents, an effect that is abrogated in thealmt12^−/−and (2) reduced the current inAtALMT12 transfectedCOS‐7 cells, strongly suggesting the direct interaction ofGABAwithAtALMT12.

   Our data show thatAtSLAH3 andAtCCCactivity is sufficient to explain the major component of extracellular anion fluxes, and unveils a possible regulatory system linkingPTgrowth modulation bypH,GABA, and [Ca²⁺]_cytthrough anionic transporters.

    

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4. Synapsins regulate brain‐derived neurotrophic factor‐mediated synaptic potentiation and axon elongation by acting on membrane rafts

   https://doi.org/10.1111/ejn.13552  

   Kao, Hung‐Teh ; Ryoo, Kanghyun ; Lin, Albert ; Janoschka, Stephen R. ; Augustine, George J. ; Porton, Barbara ; Kano, ed., Masanobu ( March 2017 , European Journal of Neuroscience)

   In neurons, intracellular membrane rafts are essential for specific actions of brain‐derived neurotrophic factor (BDNF), which include the regulation of axon outgrowth, growth cone turning and synaptic transmission. Virtually, all the actions ofBDNFare mediated by binding to its receptor, TrkB. The association of TrkB with the tyrosine kinase, Fyn, is critical for its localization to intracellular membrane rafts. Here, we show that synapsins, a family of highly amphipathic neuronal phosphoproteins, regulate membrane raft lipid composition and consequently, the ability ofBDNFto regulate axon/neurite development and potentiate synaptic transmission. In the brains of mice lacking all synapsins, the expression of bothBDNFand TrkB were increased, suggesting thatBDNF/TrkB‐mediated signaling is impaired. Consistent with this finding, synapsin‐depleted neurons exhibit altered raft lipid composition, deficient targeting of Fyn to rafts, attenuated TrkB activation, and abrogation ofBDNF‐stimulated axon outgrowth and synaptic potentiation. Conversely, overexpression of synapsins in neuroblastoma cells results in corresponding reciprocal changes in raft lipid composition, increased localization of Fyn to rafts and promotion ofBDNF‐stimulated neurite formation. In the presence of synapsins, the ratio of cholesterol to estimated total phospholipids converged to 1, suggesting that synapsins act by regulating the ratio of lipids in intracellular membranes, thereby promoting lipid raft formation. These studies reveal a mechanistic link betweenBDNFand synapsins, impacting early development and synaptic transmission.

    

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5. Coumarin‐based Fluorescent Probes for Selectively Targeting and Imaging the Endoplasmic Reticulum in Mammalian Cells

   https://doi.org/10.1111/php.12985  

   Wijesooriya, Chamari S. ; Nieszala, Megan ; Stafford, Alex ; Zimmerman, Jake R. ; Smith, Emily A. ( August 2018 , Photochemistry and Photobiology)

   Developing improved fluorescent probes for imaging the endoplasmic reticulum (ER) is necessary for structure‐activity studies of this dynamic organelle. Two coumarin‐based compounds with sulfonamide side groups were synthesized and characterized asER‐targeting probes. Their selectivity to target theERin HeLa andGM07373 mammalian cells was shown with co‐localization experiments using commercially available probes that localize in theER, mitochondria, or lysozymes. The hydrophobicity of the coumarin‐based probes was comparable to known probes that partition into theERmembrane. Their cytotoxicity in mammalian cells was low withIC50 values that range from 205 to 252 μm. The fluorescent quantum yields of the coumarin‐based probes when excited with 400 nm light were 0.60, and they have a much narrower emission spectrum (from 435 to 525 nm in methanol) than that of the only commercially availableERprobe that is exited with 400 nm light (ER‐Tracker™ Blue‐WhiteDPX). Thus, the coumarin‐based probes are more useful for multicolor imaging with yellow and red emitting fluorophores. In addition to the above benefits,ERlabeling was achieved with the coumarin‐based probes in both live cells and fixed cells, revealing their versatility for a wide range of cellular imaging applications.

    

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