The ABCs of membrane transporters in health and disease (SLC series): Introduction

Hediger, Matthias A.; Clémençon, Benjamin; Burrier, Robert E.; Bruford, Elspeth A.

doi:10.1016/j.mam.2012.12.009

Cited by 528 publications

(486 citation statements)

References 99 publications

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“…To generate a sufficient supply of amino acids to support growth, L. pneumophila promotes proteasomal degradation of polyubiquitinated proteins surrounding the pathogen vacuole (65) and relies upon the host cell amino acid transporter solute carrier (SLC) protein SLC1A5 (66). SLC proteins are responsible for shuttling nutrients across plasma, lysosome, and other organelle membranes (67). Endolysosomal compartments that fuse with the C. burnetii-containing vacuole contain numerous SLC proteins (4,68,69).…”

Section: Discussionmentioning

confidence: 99%

Complementation of Arginine Auxotrophy for Genetic Transformation of Coxiella burnetii by Use of a Defined Axenic Medium

Sandoz

Beare

Cockrell

et al. 2016

Appl Environ Microbiol

101

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Host cell-free (axenic) culture of Coxiella burnetii in acidified citrate cysteine medium-2 (ACCM-2) has provided important opportunities for investigating the biology of this naturally obligate intracellular pathogen and enabled the development of tools for genetic manipulation. However, ACCM-2 has complex nutrient sources that preclude a detailed study of nutritional factors required for C. burnetii growth. Metabolic reconstruction of C. burnetii predicts that the bacterium cannot synthesize all amino acids and therefore must sequester some from the host. To examine C. burnetii amino acid auxotrophies, we developed a nutritionally defined medium with known amino acid concentrations, termed ACCM-D. Compared to ACCM-2, ACCM-D supported longer logarithmic growth, a more gradual transition to stationary phase, and approximately 5-to 10-fold greater overall replication. Small-cell-variant morphological forms generated in ACCM-D also showed increased viability relative to that generated in ACCM-2. Lack of growth in amino acid-deficient formulations of ACCM-D revealed C. burnetii auxotrophy for 11 amino acids, including arginine. Heterologous expression of Legionella pneumophila argGH in C. burnetii permitted growth in ACCM-D missing arginine and supplemented with citrulline, thereby providing a nonantibiotic means of selection of C. burnetii genetic transformants. Consistent with bioinformatic predictions, the elimination of glucose did not impair C. burnetii replication. Together, these results highlight the advantages of a nutritionally defined medium in investigations of C. burnetii metabolism and the development of genetic tools. IMPORTANCEHost cell-free growth and genetic manipulation of Coxiella burnetii have revolutionized research of this intracellular bacterial pathogen. Nonetheless, undefined components of growth medium have made studies of C. burnetii physiology difficult and have precluded the development of selectable markers for genetic transformation based on nutritional deficiencies. Here, we describe a medium, containing only amino acids as the sole source of carbon and energy, which supports robust growth and improved viability of C. burnetii. Growth studies confirmed that C. burnetii cannot replicate in medium lacking arginine. However, genetic transformation of the bacterium with constructs containing the last two genes in the L. pneumophila arginine biosynthesis pathway (argGH) allowed growth on defined medium missing arginine but supplemented with the arginine precursor citrulline. Our results advance the field by facilitating studies of C. burnetii metabolism and allowing non-antibiotic-based selection of C. burnetii genetic transformants, an important achievement considering that selectable makers based on antibiotic resistance are limited.C oxiella burnetii is a wide-ranging bacterial pathogen that causes the zoonosis Q fever (1, 2). Humans are generally infected by inhalation of contaminated aerosols generated by domestic livestock, with sheep, goats, and dairy cattle being the prim...

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Section: Discussionmentioning

confidence: 99%

Complementation of Arginine Auxotrophy for Genetic Transformation of Coxiella burnetii by Use of a Defined Axenic Medium

Sandoz

Beare

Cockrell

et al. 2016

Appl Environ Microbiol

101

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“…The solute carrier (SLC) group comprises a diverse array of transporters grouped into at least 52 families based on function and sequence homology (1). The SLC4 family is termed the bicarbonate transporters and is subdivided into sodium-coupled cotransporters and anion exchanger subclasses.…”

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confidence: 99%

Structure of Bor1 supports an elevator transport mechanism for SLC4 anion exchangers

Thurtle‐Schmidt

Stroud

2016

Proc. Natl. Acad. Sci. U.S.A.

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Boron is essential for plant growth because of its incorporation into plant cell walls; however, in excess it is toxic to plants. Boron transport and homeostasis in plants is regulated in part by the borate efflux transporter Bor1, a member of the solute carrier (SLC) 4 transporter family with homology to the human bicarbonate transporter Band 3. Here, we present the 4.1-Å resolution crystal structure of Arabidopsis thaliana Bor1. The structure displays a dimeric architecture in which dimerization is mediated by centralized Gate domains. Comparisons with a structure of Band 3 in an outward-open state reveal that the Core domains of Bor1 have rotated inwards to achieve an occluded state. Further structural comparisons with UapA, a xanthine transporter from the nucleobase-ascorbate transporter family, show that the downward pivoting of the Core domains relative to the Gate domains may access an inward-open state. These results suggest that the SLC4, SLC26, and nucleobase-ascorbate transporter families all share an elevator transport mechanism in which alternating access is provided by Core domains that carry substrates across a membrane.T he defining feature of transporters is the ability to carry specific molecules across a membrane. The solute carrier (SLC) group comprises a diverse array of transporters grouped into at least 52 families based on function and sequence homology (1). The SLC4 family is termed the bicarbonate transporters and is subdivided into sodium-coupled cotransporters and anion exchanger subclasses. The SLC4 anion exchangers transport ions in an electroneutral manner, most commonly transporting bicarbonate in exchange for chloride. In addition to bicarbonate transporters, the SLC4 transporters include borate efflux transporters, originally discovered in plants (2, 3). Boron is an essential plant micronutrient that is taken up from the soil and participates in the formation of esters found in plant cell walls. Specifically, borate diesters cross-link a primary cell wall component, pectic polysaccharide rhamnogalacturonan II (RG-II) and, thus, contribute to plant cell wall stability (4, 5). In excess levels, however, boron is toxic to plants. The regulation of boron by transporters is therefore important for plant viability and has implications for worldwide agriculture. Indeed, there are ongoing efforts to engineer plants that are tolerant of either high or low boron levels in soil (6-8). The transport and regulation of boron levels is regulated partly by Bor1, a boron exporter that loads xylem, such that boron is transported from roots to shoots and leaves (3). The precise chemical nature boron takes during transport is not known, but is commonly assumed to be borate, an anionic form of boric acid. Bor1 is active in plants under limiting borate conditions, but is degraded under high concentrations of borate to avoid accumulation of toxic boron levels in plant shoots (9). Although the transporter function and regulation of Bor1 in response to excess borate have been defined, the mechanism by w...

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“…The solute carrier (SLC) 2 group of membrane transport proteins includes over 300 members subdivided into 52 families (1,2). These proteins are located in the plasma membrane and the membranes of intracellular organelles where they transport a variety of solutes across cell membranes.…”

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confidence: 99%

SLC17A9 Protein Functions as a Lysosomal ATP Transporter and Regulates Cell Viability

Cao

Zhao

Zhong

et al. 2014

Journal of Biological Chemistry

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Background: Lysosomes contain abundant ATP. Results: SLC17A9 transports ATP into lysosomes. SLC17A9-deficient cells exhibit lysosome dysfunction and undergo subsequent cell death. Conclusion: SLC17A9 functions as a lysosomal ATP transporter and maintains cell viability. Significance: This work identifies a molecular mechanism underlying lysosomal ATP accumulation and suggests that ATP functions not only as energy currency but plays a key role in lysosome function.

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The ABCs of membrane transporters in health and disease (SLC series): Introduction

Cited by 528 publications

References 99 publications

Complementation of Arginine Auxotrophy for Genetic Transformation of Coxiella burnetii by Use of a Defined Axenic Medium

Complementation of Arginine Auxotrophy for Genetic Transformation of Coxiella burnetii by Use of a Defined Axenic Medium

Structure of Bor1 supports an elevator transport mechanism for SLC4 anion exchangers

SLC17A9 Protein Functions as a Lysosomal ATP Transporter and Regulates Cell Viability

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