Determinants for the Subcellular Localization and Function of a Nonessential SEDS Protein

ABSTRACT The Bacillus subtilis SpoVE integral membrane protein is essential for the heat resistance of spores, probably because of its involvement in spore peptidoglycan synthesis. We found that an SpoVE-yellow fluorescent protein (YFP) fusion protein becomes localized to the forespore during the earliest stages of engulfment, and this pattern is maintained throughout sporulation. SpoVE belongs to a well-conserved family of proteins that includes the FtsW and RodA proteins of B. subtilis. These proteins are involved in bacterial shape determination, although their function is not known. FtsW is necessary for the formation of the asymmetric septum in sporulation, and we found that an FtsW-YFP fusion localized to this structure prior to the initiation of engulfment in a nonoverlapping pattern with SpoVE-cyan fluorescent protein. Since FtsW and RodA are essential for normal growth, it has not been possible to identify loss-of-function mutations that would greatly facilitate analysis of their function. We took advantage of the fact that SpoVE is not required for growth to obtain point mutations in SpoVE that block the development of spore heat resistance but that allow normal protein expression and targeting to the forespore. These mutant proteins will be invaluable tools for future experiments aimed at elucidating the function of members of the SEDS (“shape, elongation, division, and sporulation”) family of proteins.

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FtsZ from Divergent Foreign Bacteria Can Function for Cell Division in Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.00647-06 ◽

2006 ◽

Vol 188 (20) ◽

pp. 7132-7140 ◽

Cited By ~ 31

Author(s):

Masaki Osawa ◽

Harold P. Erickson

Keyword(s):

Escherichia Coli ◽

Cell Division ◽

Fluorescent Protein ◽

Yellow Fluorescent Protein ◽

Point Mutations ◽

Loss Of Function ◽

Mycoplasma Pulmonis ◽

E Coli ◽

Z Ring ◽

Ftsz Assembly

ABSTRACT FtsZs from Mycoplasma pulmonis (MpuFtsZ) and Bacillus subtilis (BsFtsZ) are only 46% and 53% identical in amino acid sequence to FtsZ from Escherichia coli (EcFtsZ). In the present study we show that MpuFtsZ and BsFtsZ can function for cell division in E. coli provided we make two modifications. First, we replaced their C-terminal tails with that from E. coli, giving the foreign FtsZ the binding site for E. coli FtsA and ZipA. Second, we selected for mutations in the E. coli genome that facilitated division by the foreign FtsZs. These suppressor strains arose at a relatively high frequency of 10−3 to 10−5, suggesting that they involve loss-of-function mutations in multigene pathways. These pathways may be negative regulators of FtsZ or structural pathways that facilitate division by slightly defective FtsZ. Related suppressor strains were obtained for EcFtsZ containing certain point mutations or insertions of yellow fluorescent protein. The ability of highly divergent FtsZs to function for division in E. coli is consistent with a two-part mechanism. FtsZ assembles the Z ring, and perhaps generates the constriction force, through self interactions; the downstream division proteins remodel the peptidoglycan wall by interacting with each other and the wall. The C-terminal peptide of FtsZ, which binds FtsA, provides the link between FtsZ assembly and peptidoglycan remodeling.

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Disparate Subcellular Localization Patterns of Pseudomonas aeruginosa Type IV Pilus ATPases Involved in Twitching Motility

Journal of Bacteriology ◽

10.1128/jb.187.3.829-839.2005 ◽

2005 ◽

Vol 187 (3) ◽

pp. 829-839 ◽

Cited By ~ 87

Author(s):

Poney Chiang ◽

Marc Habash ◽

Lori L. Burrows

Keyword(s):

Pseudomonas Aeruginosa ◽

Fluorescent Protein ◽

Protein Localization ◽

Yellow Fluorescent Protein ◽

Distribution Patterns ◽

Opportunistic Pathogen ◽

Twitching Motility ◽

Polar Localization ◽

Type Iv ◽

And Function

ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa expresses polar type IV pili (TFP), which are responsible for adhesion to various materials and twitching motility on surfaces. Twitching occurs by alternate extension and retraction of TFP, which arise from assembly and disassembly of pilin subunits at the base of the pilus. The ATPase PilB promotes pilin assembly, while the ATPase PilT or PilU or both promote pilin dissociation. Fluorescent fusions to two of the three ATPases (PilT and PilU) were functional, as shown by complementation of the corresponding mutants. PilB and PilT fusions localized to both poles, while PilU fusions localized only to the piliated pole. To identify the portion of the ATPases required for localization, sequential C-terminal deletions of PilT and PilU were generated. The conserved His and Walker B boxes were dispensable for polar localization but were required for twitching motility, showing that localization and function could be uncoupled. Truncated fusions that retained polar localization maintained their distinctive distribution patterns. To dissect the cellular factors involved in establishing polarity, fusion protein localization was monitored with a panel of TFP mutants. The localization of yellow fluorescent protein (YFP)-PilT and YFP-PilU was independent of the subunit PilA, other TFP ATPases, and TFP-associated proteins previously shown to be associated with the membrane or exhibiting polar localization. In contrast, YFP-PilB exhibited diffuse cytoplasmic localization in a pilC mutant, suggesting that PilC is required for polar localization of PilB. Finally, localization studies performed with fluorescent ATPase chimeras of PilT and PilU demonstrated that information responsible for the characteristic localization patterns of the ATPases likely resides in their N termini.

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Distribution dynamics and functional importance of NHERF1 in regulation of Mrp-2 trafficking in hepatocytes

AJP Cell Physiology ◽

10.1152/ajpcell.00011.2014 ◽

2014 ◽

Vol 307 (8) ◽

pp. C727-C737 ◽

Cited By ~ 11

Author(s):

Serhan Karvar ◽

Jo Suda ◽

Lixin Zhu ◽

Don C. Rockey

Keyword(s):

Binding Site ◽

Deletion Mutant ◽

Fluorescent Protein ◽

Yellow Fluorescent Protein ◽

Secretory Response ◽

Scaffolding Protein ◽

Pdz Domains ◽

Canalicular Membrane ◽

Infected Cells ◽

And Function

Na+/H+ exchanger regulatory factor 1 (NHERF1) is a multifunctional scaffolding protein that interacts with receptors and ion transporters in its PDZ domains and with the ezrin-radixin-moesin (ERM) family of proteins in its COOH terminus. The role of NHERF1 in hepatocyte function remains largely unknown. We examine the distribution and physiological significance of NHERF1 and multidrug resistance-associated protein 2 (Mrp-2) in hepatocytes. A WT radixin binding site mutant (F355R) and NHERF1 PDZ1 and PDZ2 domain adenoviral mutant constructs were tagged with yellow fluorescent protein and expressed in polarized hepatocytes to study localization and function of NHERF1. Cellular distribution of NHERF1 and radixin was visualized by fluorescence microscopy. A 5-chloromethylfluorescein diacetate (CMFDA) assay was used to characterize Mrp-2 function. Similar to Mrp-2, WT NHERF1 and the NHERF1 PDZ2 deletion mutant were localized to the canalicular membrane. In contrast, the radixin binding site mutant (F355R) and the NHERF1 PDZ1 deletion mutant, which interacts poorly with Mrp-2, were rarely associated with the canalicular membrane. Knockdown of NHERF1 led to dramatically impaired CMFDA secretory response. Use of CMFDA showed that the NHERF1 PDZ1 and F355R mutants were devoid of a secretory response, while WT NHERF1-infected cells exhibited increased secretion of glutathione-methylfluorescein. The data indicate that NHERF1 interacts with Mrp-2 via the PDZ1 domain of NHERF1 and, furthermore, that NHERF1 is essential for maintaining the localization and function of Mrp-2.

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Clp and Lon Proteases Occupy Distinct Subcellular Positions in Bacillus subtilis

Journal of Bacteriology ◽

10.1128/jb.00590-08 ◽

2008 ◽

Vol 190 (20) ◽

pp. 6758-6768 ◽

Cited By ~ 38

Author(s):

Lyle A. Simmons ◽

Alan D. Grossman ◽

Graham C. Walker

Keyword(s):

Bacillus Subtilis ◽

Stress Responses ◽

Fluorescent Protein ◽

Yellow Fluorescent Protein ◽

Normal Growth ◽

Temporal Organization ◽

Hexameric Atpase ◽

Fluorescent Moiety ◽

Green Fluorescent

ABSTRACT Among other functions, ATP-dependent proteases degrade misfolded proteins and remove several key regulatory proteins necessary to activate stress responses. In Bacillus subtilis, ClpX, ClpE, and ClpC form homohexameric ATPases that couple to the ClpP peptidase. To understand where these peptidases and ATPases localize in living cells, each protein was fused to a fluorescent moiety. We found that ClpX-GFP (green fluorescent protein) and ClpP-GFP localized as focal assemblies in areas that were not occupied by the nucleoid. We found that the percentage of cells with ClpP-GFP foci increased following heat shock independently of protein synthesis. We determined that ClpE-YFP (yellow fluorescent protein) and ClpC-YFP formed foci coincident with nucleoid edges, usually near cell poles. Furthermore, we found that ClpQ-YFP (HslV) localized as small foci, usually positioned near the cell membrane. We found that ClpQ-YFP foci were dependent on the presence of the cognate hexameric ATPase ClpY (HslU). Moreover, we found that LonA-GFP is coincident with the nucleoid during normal growth and that LonA-GFP also localized to the forespore during development. We also investigated LonB-GFP and found that this protein localized to the forespore membrane early in development, followed by localization throughout the forespore later in development. Our comprehensive study has shown that in B. subtilis several ATP-fueled proteases occupy distinct subcellular locations. With these data, we suggest that substrate specificity could be determined, in part, by the spatial and temporal organization of proteases in vivo.

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Localization and Expression of MreB in Vibrio parahaemolyticus under Different Stresses

Applied and Environmental Microbiology ◽

10.1128/aem.01020-08 ◽

2008 ◽

Vol 74 (22) ◽

pp. 7016-7022 ◽

Cited By ~ 24

Author(s):

Shen-Wen Chiu ◽

Shau-Yan Chen ◽

Hin-chung Wong

Keyword(s):

Stationary Phase ◽

Vibrio Parahaemolyticus ◽

Spatial Organization ◽

Fluorescent Protein ◽

Morphological Changes ◽

Yellow Fluorescent Protein ◽

Normal Growth ◽

Growth Conditions ◽

Cellular Stress Response ◽

Vbnc State

ABSTRACT MreB, the homolog of eukaryotic actin, may play a vital role when prokaryotes cope with stress by altering their spatial organization, including their morphology, subcellular architecture, and localization of macromolecules. This study investigates the behavior of MreB in Vibrio parahaemolyticus under various stresses. The behavior of MreB was probed using a yellow fluorescent protein-MreB conjugate in merodiploid strain SC9. Under normal growth conditions, MreB formed helical filaments in exponential-phase cells. The shape of starved or stationary-phase cells changed from rods to small spheroids. The cells differentiated into the viable but nonculturable (VBNC) state with small spherical cells via a “swelling-waning” process. In all cases, drastic remodeling of the MreB cytoskeleton was observed. MreB helices typically were loosened and fragmented into short filaments, arcs, and spots in bacteria under these stresses. The disintegrated MreB exhibited a strong tendency to attach to the cytoplasmic membrane. The expression of mreB generally declined in bacteria in the stationary phase and under starvation but was upregulated during the initial periods of cold shock and VBNC state differentiation and decreased afterwards. Our findings demonstrated the behavior of MreB in the morphological changes of V. parahaemolyticus under intrinsic or extrinsic stresses and may have important implications for studying the cellular stress response and aging.

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Genomic and physiological analyses of the zebrafish atrioventricular canal reveal molecular building blocks of the secondary pacemaker region

Cellular and Molecular Life Sciences ◽

10.1007/s00018-021-03939-y ◽

2021 ◽

Author(s):

Karim Abu Nahia ◽

Maciej Migdał ◽

T. Alexander Quinn ◽

Kar-Lai Poon ◽

Maciej Łapiński ◽

...

Keyword(s):

Epithelial To Mesenchymal Transition ◽

Fluorescent Protein ◽

Building Blocks ◽

Transgenic Zebrafish ◽

Loss Of Function ◽

Atrioventricular Canal ◽

Protein Coding ◽

Mesenchymal Transition ◽

Molecular Building Blocks ◽

And Function

AbstractThe atrioventricular canal (AVC) is the site where key structures responsible for functional division between heart regions are established, most importantly, the atrioventricular (AV) conduction system and cardiac valves. To elucidate the mechanism underlying AVC development and function, we utilized transgenic zebrafish line sqet31Et expressing EGFP in the AVC to isolate this cell population and profile its transcriptome at 48 and 72 hpf. The zebrafish AVC transcriptome exhibits hallmarks of mammalian AV node, including the expression of genes implicated in its development and those encoding connexins forming low conductance gap junctions. Transcriptome analysis uncovered protein-coding and noncoding transcripts enriched in AVC, which have not been previously associated with this structure, as well as dynamic expression of epithelial-to-mesenchymal transition markers and components of TGF-β, Notch, and Wnt signaling pathways likely reflecting ongoing AVC and valve development. Using transgenic line Tg(myl7:mermaid) encoding voltage-sensitive fluorescent protein, we show that abolishing the pacemaker-containing sinoatrial ring (SAR) through Isl1 loss of function resulted in spontaneous activation in the AVC region, suggesting that it possesses inherent automaticity although insufficient to replace the SAR. The SAR and AVC transcriptomes express partially overlapping species of ion channels and gap junction proteins, reflecting their distinct roles. Besides identifying conserved aspects between zebrafish and mammalian conduction systems, our results established molecular hallmarks of the developing AVC which underlies its role in structural and electrophysiological separation between heart chambers. This data constitutes a valuable resource for studying AVC development and function, and identification of novel candidate genes implicated in these processes.

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The Tension-sensitive Ion Transport Activity of MSL8 is Critical for its Function in Pollen Hydration and Germination

10.1101/084988 ◽

2016 ◽

Author(s):

Eric S. Hamilton ◽

Elizabeth S. Haswell

Keyword(s):

Pollen Germination ◽

Pollen Viability ◽

Point Mutations ◽

Normal Growth ◽

Loss Of Function ◽

Transport Activity ◽

Wild Type ◽

Gated Channel ◽

In The Wild ◽

Pore Lining

AbstractAll cells respond to osmotic challenges, including those imposed during normal growth and development. Mechanosensitive (MS) ion channels provide a conserved mechanism for regulating osmotic forces by conducting ions in response to increased membrane tension. We previously demonstrated that the MS ion channel MscS-Like 8 (MSL8) is required for pollen to survive multiple osmotic challenges that occur during the normal process of fertilization, and that it can inhibit pollen germination. However, it remained unclear whether these physiological functions required ion flux through a mechanically gated channel provided by MSL8. We introduced two point mutations into the predicted pore-lining domain of MSL8 that disrupted normal channel function in different ways. The Ile711Ser mutation increased the tension threshold of the MSL8 channel while leaving conductance unchanged, and the Phe720Leu mutation severely disrupted the MSL8 channel. Both of these mutations impaired the ability of MSL8 to preserve pollen viability during hydration and to maintain the integrity of the pollen tube when expressed at endogenous levels. When overexpressed in a msl8-4 null background, MSL8I711S could partially rescue loss-of-function phenotypes, while MSL8F720L could not. When overexpressed in the wild type Ler background, MSL8I711S suppressed pollen germination, similar to wild type MSL8. In contrast, MSL8F720L failed to suppress pollen germination and increased pollen bursting, thereby phenocopying the msl8-4 mutant. Thus, an intact MSL8 channel is required to for normal pollen function during hydration and germination. These data establish MSL8 as the first plant MS channel to fulfill previously established criteria for assignment as a mechanotransducer.

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The CiaRH System of Streptococcus pneumoniae Prevents Lysis during Stress Induced by Treatment with Cell Wall Inhibitors and by Mutations in pbp2x Involved in β-Lactam Resistance

Journal of Bacteriology ◽

10.1128/jb.188.5.1959-1968.2006 ◽

2006 ◽

Vol 188 (5) ◽

pp. 1959-1968 ◽

Cited By ~ 65

Author(s):

Thorsten Mascher ◽

Manuel Heintz ◽

Dorothea Zähner ◽

Michelle Merai ◽

Regine Hakenbeck

Keyword(s):

Cell Wall ◽

Streptococcus Pneumoniae ◽

Growth Phase ◽

Point Mutations ◽

Normal Growth ◽

Stationary Growth Phase ◽

Clinical Isolates ◽

Loss Of Function ◽

Beta Lactam ◽

Stationary Growth

ABSTRACT The two-component signal-transducing system CiaRH of Streptococcus pneumoniae plays an important role during the development of beta-lactam resistance in laboratory mutants. We show here that a functional CiaRH system is required for survival under many different lysis-inducing conditions. Mutants with an activated CiaRH system were highly resistant to lysis induced by a wide variety of early and late cell wall inhibitors, such as cycloserine, bacitracin, and vancomycin, and were also less susceptible to these drugs. In contrast, loss-of-function CiaRH mutants were hypersusceptible to these drugs and were apparently unable to maintain a stationary growth phase in normal growth medium and under choline deprivation as well. Moreover, disruption of CiaR in penicillin-resistant mutants with an altered pbp2x gene encoding low-affinity PBP2x resulted in severe growth defects and rapid lysis. This phenotype was observed with pbp2x genes containing point mutations selected in the laboratory and with highly altered mosaic pbp2x genes from penicillin-resistant clinical isolates as well. This documents for the first time that PBP2x mutations required for development of beta-lactam resistance are functionally not neutral and are tolerated only in the presence of the CiaRH system. This might explain why cia mutations have not been observed in penicillin-resistant clinical isolates. The results document that the CiaRH system is required for maintenance of the stationary growth phase and for prevention of autolysis triggered under many different conditions, suggesting a major role for this system in ensuring cell wall integrity.

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Arabidopsis sucrose synthase localization indicates a primary role in sucrose translocation in phloem

Journal of Experimental Botany ◽

10.1093/jxb/erz539 ◽

2019 ◽

Vol 71 (6) ◽

pp. 1858-1869 ◽

Cited By ~ 4

Author(s):

Danyu Yao ◽

Eliana Gonzales-Vigil ◽

Shawn D Mansfield

Keyword(s):

Sucrose Synthase ◽

Fluorescent Protein ◽

Yellow Fluorescent Protein ◽

Normal Growth ◽

Primary Role ◽

Hypoxic Conditions ◽

Companion Cells ◽

Related Transcription Factor ◽

Xylem Tissue ◽

Enzyme Families

Abstract Sucrose synthase (SuSy) is one of two enzyme families capable of catalyzing the first degradative step in sucrose utilization. Several earlier studies examining SuSy mutants in Arabidopsis failed to identify obvious phenotypic abnormalities compared with wild-type plants in normal growth environments, and as such a functional role for SuSy in the previously proposed cellulose biosynthetic process remains unclear. Our study systematically evaluated the precise subcellular localization of all six isoforms of Arabidopsis SuSy via live-cell imaging. We showed that yellow fluorescent protein (YFP)-labeled SuSy1 and SuSy4 were expressed exclusively in phloem companion cells, and the sus1/sus4 double mutant accumulated sucrose under hypoxic conditions. SuSy5 and SuSy6 were found to be parietally localized in sieve elements and restricted only to the cytoplasm. SuSy2 was present in the endosperm and embryo of developing seeds, and SuSy3 was localized to the embryo and leaf stomata. No single isoform of SuSy was detected in developing xylem tissue of elongating stem, the primary site of cellulose deposition in plants. SuSy1 and SuSy4 were also undetectable in the protoxylem tracheary elements, which were induced by the vascular-related transcription factor VND7 during secondary cell wall formation. These findings implicate SuSy in the biological events related to sucrose translocation in phloem.

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