More Like this

1. 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.

    

   more » « less
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.

    

   more » « less
3. 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.

    

   more » « less
4. A PEX5 missense allele preferentially disrupts PTS 1 cargo import into Arabidopsis peroxisomes

   https://doi.org/10.1002/pld3.128  

   Patel, Khushali J. ; Kao, Yun‐Ting ; Llinas, Roxanna J. ; Bartel, Bonnie ( March 2019 , Plant Direct)

   The sorting of eukaryotic proteins to various organellar destinations requires receptors that recognize cargo protein targeting signals and facilitate transport into the organelle. One such receptor is the peroxinPEX5, which recruits cytosolic cargo carrying a peroxisome‐targeting signal (PTS) type 1 (PTS1) for delivery into the peroxisomal lumen (matrix). In plants and mammals,PEX5 is also indirectly required for peroxisomal import of proteins carrying aPTS2 signal becausePEX5 binds thePTS2 receptor, bringing the associatedPTS2 cargo to the peroxisome along withPTS1 cargo. DespitePEX5 being thePTS1 cargo receptor, previously identified Arabidopsispex5mutants display either impairment of bothPTS1 andPTS2 import or defects only inPTS2 import. Here, we report the first Arabidopsispex5mutant with an exclusivePTS1 import defect. In addition to markedly diminishedGFP‐PTS1 import and decreased pex5‐2 protein accumulation, thispex5‐2mutant shows typical peroxisome‐related defects, including inefficient β‐oxidation and reduced growth. Growth at reduced or elevated temperatures ameliorated or exacerbatedpex5‐2peroxisome‐related defects, respectively, without markedly changing pex5‐2 protein levels. In contrast to the diminishedPTS1 import,PTS2 processing was only slightly impaired andPTS2‐GFPimport appeared normal inpex5‐2. This finding suggests that even minor peroxisomal localization of thePTS1 proteinDEG15, thePTS2‐processing protease, is sufficient to maintain robustPTS2 processing.

    

   more » « less
5. A microcin processing peptidase‐like protein of the cyanobacterium Synechococcus elongatus is essential for secretion of biofilm‐promoting proteins

   https://doi.org/10.1111/1758-2229.12751  

   Parnasa, Rami ; Sendersky, Eleonora ; Simkovsky, Ryan ; Waldman Ben‐Asher, Hiba ; Golden, Susan S. ; Schwarz, Rakefet ( March 2019 , Environmental Microbiology Reports)

   Small secreted compounds, e.g. microcins, are characterized by a double‐glycine (GG) secretion motif that is cleaved off upon maturation. Genomic analysis suggests that small proteins that possess a GG motif are widespread in cyanobacteria; however, the roles of these proteins are largely unknown. Using a biofilm‐proficient mutant of the cyanobacteriumSynechococcus elongatusPCC 7942 in which the constitutive biofilm self‐suppression mechanism is inactivated, we previously demonstrated that four small proteins,Enablebiofilmformation with aGG motif (EbfG1‐4), each with a GG motif, enable biofilm formation. Furthermore, a peptidase belonging to the C39 family,PeptidasetransporterenablingBiofilm (PteB), is required for secretion of these proteins. Here, we show that the microcin processing peptidase‐like protein encoded by gene Synpcc7942_1127 is also required for biofilm development – inactivation of this gene in the biofilm‐proficient mutant abrogates biofilm development. Additionally, this peptidase‐like protein (denoted EbfE – enables biofilm formation peptidase) is required for secretion of the EbfG biofilm‐promoting small proteins. Given their protein‐domain characteristics, we suggest that PteB and EbfE take part in a maturation‐secretion system, with PteB being located to the cell membrane while EbfE is directed to the periplasmic space via its secretion signal.

    

   more » « less