Regulation of the
            <i>Escherichia coli</i>
            water channel gene
            <i>aqpZ</i>

Calamita, Giuseppe; Kempf, Bettina; Bonhivers, Mélanie; Bishai, William R.; Bremer, Erhard; Agre, Peter

doi:10.1073/pnas.95.7.3627

Cited by 83 publications

(46 citation statements)

References 33 publications

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“…As reported previously (4), expression of the fusion increased markedly during the late exponential growth phase ( Fig. 1 shows both the plot used by Calamita and colleagues [4] [ Fig. 1A] and a Monod or differential plot [11] [Fig.…”

supporting

confidence: 53%

Aquaporin Z of Escherichia coli : Reassessment of Its Regulation and Physiological Role

et al. 2002

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Transcription of an aqpZ-lac fusion in a single copy on the Escherichia coli chromosome increased as cells entered the stationary growth phase. This was true in a variety of media, and increased transcription in enriched medium required the RpoS sigma factor. Expression of the aqpZ-lac fusion was not affected by up-or downshifts in osmolality. Disruption of aqpZ had no detectable adverse effects.Aquaporins belong to a large family of proteins that increase the rate of diffusion of water and glycerol across cell membranes (18,22,24). They are prominent in multicellular eukaryotic organisms, whose large size and need for rapid water movement make such proteins essential (17,25). Aquaporins (but not glyceroporins) occur only sporadically in bacteria and archaea. For example, aqpZ occurs in all four Escherichia coli strains for which whole genome sequences are available and in Shigella flexneri, but it does not occur in the closely related enteric bacterium Salmonella enterica serovar Typhimurium or in the ␥-proteobacterium Yersinia pestis (E. coli Genome Project, University of Wisconsin-Madison, http://www.genome .wisc.edu/). Moreover, aqpZ appears to be missing from Ͼ80% of the 69 bacterial and archaeal genomes that have been completely sequenced (National Center for Biotechnology Information website, http://www.ncbi.nlm.nih.gov/cgi-bin/Entrez /genom_table_cgi). It is not clear whether small cells that lack internal organelles require aquaporins or whether unmediated diffusion of water across their cytoplasmic membranes is sufficient.The aqpZ gene of E. coli was isolated by homology cloning (3). Calamita and colleagues (4) studied regulation of expression of this gene by using a plasmid carrying an aqpZ-lacZ fusion. They reported that aqpZ expression was induced very sharply in the middle of the exponential growth phase and declined thereafter. Calamita and colleagues reported that an aqpZ-null strain of E. coli (aqpZ::lacZ-kan) formed mostly small colonies on Luria-Bertani (LB) agar containing kanamycin and that it showed decreased viability upon prolonged incubation at osmolalities between 80 and 240 mosmolal.Transcription of aqpZ is increased in stationary phase. To reexamine control of E. coli aqpZ expression, we constructed a strain carrying a single copy of an aqpZ-lac transcriptional fusion stably integrated on the chromosome (7). To create the fusion, aqpZ, which had been amplified by PCR from the genome of strain MG1655, was cleaved with PvuII, resulting in destruction of the sixth codon. The upstream fragment, which carries 400 bp 5Ј of the translational start site for aqpZ, was cloned into pRS551 (19) to yield pJES1320. The fusion was integrated at the trp locus as previously described (7) and then introduced into prototrophic strain NCM1458 (also known as RK4353 [21]) by P1-mediated transduction to yield strain NCM3342 [Kan r -⌽(aqpZЈ-Јlac)]. As reported previously (4

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confidence: 53%

Aquaporin Z of Escherichia coli : Reassessment of Its Regulation and Physiological Role

et al. 2002

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“…In most bacteria that have two MIP channels, such as E. coli, one is a glycerol facilitator (GlpF), involved in glycerol uptake for its catabolism as a source for carbon and energy, and the second one is an aquaporin (AqpZ in E. coli). The physiological role of E. coli AqpZ is not fully understood, but it is believed to facilitate water efflux during rapid cell proliferation and hypo-osmotic conditions (76,77,132). MIP channels are highly common in plants; Arabidopsis has 36 MIP channels in four subfamilies (98,263,528).…”

Section: Mip Channelsmentioning

confidence: 99%

Osmotic Stress Signaling and Osmoadaptation in Yeasts

Hohmann

2002

Microbiol Mol Biol Rev

1,519

1,440

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The ability to adapt to altered availability of free water is a fundamental property of living cells. The principles underlying osmoadaptation are well conserved. The yeast Saccharomyces cerevisiae is an excellent model system with which to study the molecular biology and physiology of osmoadaptation. Upon a shift to high osmolarity, yeast cells rapidly stimulate a mitogen-activated protein (MAP) kinase cascade, the high-osmolarity glycerol (HOG) pathway, which orchestrates part of the transcriptional response. The dynamic operation of the HOG pathway has been well studied, and similar osmosensing pathways exist in other eukaryotes. Protein kinase A, which seems to mediate a response to diverse stress conditions, is also involved in the transcriptional response program. Expression changes after a shift to high osmolarity aim at adjusting metabolism and the production of cellular protectants. Accumulation of the osmolyte glycerol, which is also controlled by altering transmembrane glycerol transport, is of central importance. Upon a shift from high to low osmolarity, yeast cells stimulate a different MAP kinase cascade, the cell integrity pathway. The transcriptional program upon hypo-osmotic shock seems to aim at adjusting cell surface properties. Rapid export of glycerol is an important event in adaptation to low osmolarity. Osmoadaptation, adjustment of cell surface properties, and the control of cell morphogenesis, growth, and proliferation are highly coordinated processes. The Skn7p response regulator may be involved in coordinating these events. An integrated understanding of osmoadaptation requires not only knowledge of the function of many uncharacterized genes but also further insight into the time line of events, their interdependence, their dynamics, and their spatial organization as well as the importance of subtle effects

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“…GlpF, like the mammalian aquaglyceroporins, has been shown to transport glycerol by a porelike mechanism. AqpZ, like mammalian and plant aquaporins, is a selective water channel, and AqpZ is operative during rapid growth (48). The importance of the aquaporin-aquaglyceroporin dualism is being explored in E. coli and may provide insight into their presence in higher organisms (Fig.…”

Section: Minireview: Aquaporins Blueprints For Cellular Plumbing Sysmentioning

confidence: 99%

The Aquaporins, Blueprints for Cellular Plumbing Systems

Agre

Bonhivers²,

Borgnia³

1998

Journal of Biological Chemistry

Self Cite

425

281

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Membrane Water PermeabilityPlasma membranes provide an effective barrier to the extracellular environment. Water was long believed to move through lipid bilayers by simple diffusion; however, membranes from different tissues vary in their permeability to water. The variability is particularly evident in mammalian kidney where proximal tubules and descending thin limbs of Henle's loop have constitutively high water permeability and are responsible for reabsorption of more than 150 liters per day in adult humans. In contrast, ascending thin limbs have very low water permeability. Renal distal tubules empty into collecting ducts where stimulation with vasopressin causes an increase in water permeability (see Ref. 1 for review). These observations led to the suggestion that specialized water transport molecules must exist in membranes with intrinsically high water permeability. Nevertheless, despite extensive studies, the molecular identity of water transport proteins remained elusive until recently.The well defined features of membrane water permeability permitted serendipitous identification of the first known water channel. While purifying the 32-kDa subunit of the red cell Rh blood group antigen, a new 28-kDa polypeptide was discovered (2). Detailed biochemical studies of this newly identified tetrameric membrane protein were made easy by its low solubility in N-lauroylsarcosine, which permitted simple purification (3). The abundance of the protein in rat renal proximal tubules and descending thin limbs (2) sparked the idea that the 28-kDa polypeptide may be the long sought water channel, and its unique N-terminal amino acid sequence permitted cloning from an erythroid cDNA library (4). Functional Analyses of AQP1The Xenopus oocyte expression system has been extremely useful for study of water transport. Oocytes injected with cRNA for the 28-kDa polypeptide exhibit remarkably high osmotic water permeability (P f ϳ200 ϫ 10 Ϫ4 cm s Ϫ1) and rapidly explode in hypotonic buffer (Fig. 1), whereas control oocytes exhibit minimal permeability (5). First referred to as "CHIP28," this protein is now designated aquaporin-1 (AQP1) 1 by the Human Genome Nomenclature Committee (see http://www.gene.ucl.ac.uk/nomenclature). Despite its large water permeability, AQP1 failed to confer a measurable increase in membrane currents (5). Consistent with these results, highly purified AQP1 protein reconstituted into proteoliposomes exhibits high unit water permeability (P f ϳ3 ϫ 10 9 water molecules subunit Ϫ1 s Ϫ1 ), whereas permeation by other small solutes or even protons was undetectable (6). The prevailing view is that AQP1 is a constitutively active, water-selective pore that permits osmotically driven movement of water. A report that forskolin induces a cation current in AQP1-expressing oocytes (7) was not reproduced by multiple other scientific groups. Permeation by CO 2 has recently been proposed, because rates of pH change are about 40% higher in oocytes expressing AQP1 (8). Permeation by O 2 , nitric oxide, and other gases is...

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Regulation of the Escherichia coli water channel gene aqpZ

Cited by 83 publications

References 33 publications

Aquaporin Z of Escherichia coli : Reassessment of Its Regulation and Physiological Role

Aquaporin Z of Escherichia coli : Reassessment of Its Regulation and Physiological Role

Osmotic Stress Signaling and Osmoadaptation in Yeasts

The Aquaporins, Blueprints for Cellular Plumbing Systems

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