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The oligopeptide ABC-importers are essential communication channels in Gram-positive bacteria.
Slamti, L, Lereclus, D
Research in microbiology. 2019;(8):338-344
Abstract
The transport of peptides in microorganisms plays an important role in their physiology and behavior, both as a nutrient source and as a proxy to sense their environment. This latter function is evidenced in Gram-positive bacteria where cell-cell communication is mediated by small peptides. Here, we highlight the importance of the oligopeptide permease (Opp) systems in the various major processes controlled by signaling peptides, such as sporulation, virulence and conjugation. We underline that the functioning of these communication systems is tightly linked to the developmental status of the bacteria via the regulation of opp gene expression by transition phase regulators.
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2.
Dissecting the Proton Transport Pathway in Oral Squamous Cell Carcinoma: State of the Art and Theranostics Implications.
Lorenzo-Pouso, AI, Pérez-Sayáns, M, Rodríguez-Zorrilla, S, Chamorro-Petronacci, C, García-García, A
International journal of molecular sciences. 2019;(17)
Abstract
Cancer cells overexpress proton exchangers at the plasma membrane in order acidify the extracellular matrix and maintain the optimal pH for sustaining cancer growth. Among the families of proton exchangers implicated in carcinogenesis, carbonic anhydrases (CAs), monocarboxylate transporters (MCTs), Na+/H+ exchangers (NHEs), sodium bicarbonate cotransporters (NBCs), and vacuolar ATPases (V-ATPases) are highlighted. Considerable research has been carried out into the utility of the understanding of these machineries in the diagnosis and prognosis of several solid tumors. In addition, as therapeutic targets, the interference of their functions has contributed to the discovery or optimization of cancer therapies. According to recent reports, the study of these mechanisms seems promising in the particular case of oral squamous cell carcinoma (OSCC). In the present review, the latest advances in these fields are summarized, in particular, the usefulness of proton exchangers as potential prognostic biomarkers and therapeutic targets in OSCC.
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3.
[Thiamine-responsive megaloblastic anemia or Rogers syndrome: A literature review].
Lu, H, Lu, H, Vaucher, J, Tran, C, Vollenweider, P, Castioni, J
La Revue de medecine interne. 2019;(1):20-27
Abstract
Thiamine-responsive megaloblastic anemia (TRMA), also known as Rogers syndrome, is a rare autosomal recessive disease characterized by three main components: megaloblastic anemia, diabetes mellitus and sensorineural deafness. Those features occur in infancy but may arise during adolescence. Diagnosis relies on uncovering genetic variations (alleles) in the SLC19A2 gene, encoding for a high affinity thiamine transporter. This transporter is essentially present in hematopoietic stem cells, pancreatic beta cells and inner ear cells, explaining the clinical manifestations of the disease. Based on a multidisciplinary approach, treatment resides on lifelong thiamine oral supplementation at pharmacological doses, which reverses anemia and may delay development of diabetes. However, thiamine supplementation does not alleviate already existing hearing defects.
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4.
PIN-FORMED and PIN-LIKES auxin transport facilitators.
Sauer, M, Kleine-Vehn, J
Development (Cambridge, England). 2019;(15)
Abstract
The phytohormone auxin influences virtually all aspects of plant growth and development. Auxin transport across membranes is facilitated by, among other proteins, members of the PIN-FORMED (PIN) and the structurally similar PIN-LIKES (PILS) families, which together govern directional cell-to-cell transport and intracellular accumulation of auxin. Canonical PIN proteins, which exhibit a polar localization in the plasma membrane, determine many patterning and directional growth responses. Conversely, the less-studied non-canonical PINs and PILS proteins, which mostly localize to the endoplasmic reticulum, attenuate cellular auxin responses. Here, and in the accompanying poster, we provide a brief summary of current knowledge of the structure, evolution, function and regulation of these auxin transport facilitators.
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5.
Intracellular phosphate homeostasis - A short way from metabolism to signaling.
Fabiańska, I, Bucher, M, Häusler, RE
Plant science : an international journal of experimental plant biology. 2019;:57-67
Abstract
Phosphorus in plant cells occurs in inorganic form as both ortho- and pyrophosphate or bound to organic compounds, like e.g., nucleotides, phosphorylated metabolites, phospholipids, phosphorylated proteins, or phytate as P storage in the vacuoles of seeds. Individual compartments of the cell are surrounded by membranes that are selective barriers to avoid uncontrolled solute exchange. A controlled exchange of phosphate or phosphorylated metabolites is accomplished by specific phosphate transporters (PHTs) and the plastidial phosphate translocator family (PTs) of the inner envelope membrane. Plastids, in particular chloroplasts, are the site of various anabolic sequences of enzyme-catalyzed reactions. Apart from their role in metabolism PHTs and PTs are presumed to be also involved in communication between organelles and plant organs. Here we will focus on the integration of phosphate transport and homeostasis in signaling processes. Recent developments in this field will be critically assessed and potential future developments discussed. In particular, the occurrence of various plastid types in one organ (i.e. the leaf) with different functions with respect to metabolism or sensing, as has been documented recently following a tissue-specific proteomics approach (Beltran et al., 2018), will shed new light on functional aspects of phosphate homeostasis.
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6.
A Delicate Connection: c-di-AMP Affects Cell Integrity by Controlling Osmolyte Transport.
Commichau, FM, Gibhardt, J, Halbedel, S, Gundlach, J, Stülke, J
Trends in microbiology. 2018;(3):175-185
Abstract
Bacteria use second-messenger molecules to adapt to their environment. Several second messengers, among them cyclic di-AMP (c-di-AMP), have been discovered and intensively studied. Interestingly, c-di-AMP is essential for growth of Gram-positive bacteria such as Bacillus subtilis, Listeria monocytogenes, and Staphylococcus aureus. Many studies demonstrated that perturbation of c-di-AMP metabolism affects the integrity of the bacterial cell envelope. Therefore, it has been assumed that the nucleotide is essential for proper cell envelope synthesis. In this Opinion paper, we propose that the cell envelope phenotypes caused by perturbations of c-di-AMP metabolism can be interpreted differently: c-di-AMP might indirectly control cell envelope integrity by modulating the turgor, a physical variable that needs to be tightly adjusted. We also discuss open questions related to c-di-AMP metabolism that need to be urgently addressed by future studies.
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7.
Mechanisms of phloem loading.
Zhang, C, Turgeon, R
Current opinion in plant biology. 2018;:71-75
Abstract
The complex form of higher plants requires continuous, balanced transport of nutrients in the phloem. The initial step of transferring sugars, amino acids, and other materials from photosynthetic cells to the conducting sieve tubes is known as phloem loading. Three phloem loading mechanisms have been described. The first involves release of sucrose into the apoplast and subsequent retrieval by the phloem. The initial release step in this process is now known to be mediated by a new class of transporters, the SWEET proteins. In the other two loading mechanisms, polymer trapping and diffusion, sucrose passes into the phloem through cytoplasmic channels, the plasmodesmata. Recent models have shed additional light on these mechanisms and their ability to sustain the growth of even the tallest trees.
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8.
SLC19A3 Gene Defects Sorting the Phenotype and Acronyms: Review.
Alfadhel, M, Tabarki, B
Neuropediatrics. 2018;(2):83-92
Abstract
Thiamine metabolism dysfunction syndrome type 2 is also known by other terms including: "SCL19A3 gene defect," "biotin-responsive basal ganglia disease" (BBGD), and "biotin-thiamine-responsive basal ganglia disease" (BTBGD). The worldwide incidence and prevalence of this disorder are unknown, but the syndrome has primarily been reported in Saudi Arabia (52% of reported cases). It is caused by a defect in thiamine transporter 2 (hTHTR2), which is encoded by the SLC19A3 gene. The clinical presentations of these syndromes are heterogeneous and are likely related to the age of onset. They can be classified into three major categories: classical childhood BBGD; early-infantile Leigh-like syndrome/atypical infantile spasms; and adult Wernicke's-like encephalopathy. These variable phenotypes have common features in that all are triggered by stressors, such as fever, trauma, or vaccinations. Affected brain areas include the basal ganglia, cerebral cortex, thalamus, and periaqueductal regions. Free thiamine is a potential biomarker for diagnosis and monitoring of treatment. Definitive diagnosis is usually made by molecular testing for the SLC19A3 gene defect, and treatment consists of thiamine alone or in combination with biotin for life. In this report, we review all reported cases of the SLC19A3 gene defect, discuss the history, epidemiology, metabolic pathways, clinical phenotypes, biochemical abnormalities, brain pathology, diagnosis, genetic issues, and treatment of this devastating disorder. Finally, we recommend instituting an international registry to further the basic scientific and clinical research to elucidate multiple unanswered questions about SLC19A3 gene syndromes.
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9.
Organic Chemistry Research on the Mechanistic Elucidation of Iron Acquisition in Barley.
Namba, K, Murata, Y
Biological & pharmaceutical bulletin. 2018;(10):1502-1507
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Abstract
An organic chemistry approach to the mechanistic elucidation of iron acquisition in graminaceous plants is introduced here. To elucidate this detailed mechanism using phytosiderophores, the efficient synthesis of 2'-deoxymugineic acid (DMA), a phytosiderophore of rice, was established. The synthetic DMA was confirmed to have similar iron transport activity to that of natural mugineic acid (MA). It was also revealed that the addition of synthetic DMA, along with iron, to a rice hydroponic solution enabled the rice to grow well even under an alkaline condition, and DMA clearly showed its high potential as a fertilizer to improve food production. On the other hand, the 2'-hydroxy group of MA was confirmed to serve as a point of introduction for labeling, allowing the synthesis of various mugineic acid derivatives as molecular probes. The incorporation of fluorescent mugineic acid into cells allowed them to be clearly observed by fluorescence confocal analysis, and this provided the first direct experimental evidence of transporter-mediated internalization of mugineic acid into cells.
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10.
Transport of Amino Acids across the Vacuolar Membrane of Yeast: Its Mechanism and Physiological Role.
Kawano-Kawada, M, Kakinuma, Y, Sekito, T
Biological & pharmaceutical bulletin. 2018;(10):1496-1501
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Abstract
In yeast cells growing under nutrient-rich condition approximately 50% of total amino acids are accumulated in the vacuoles; however, the composition of amino acids in the cytosol and in the vacuoles is quite different. The vacuoles, like lysosomes, degrade proteins transported into their lumen and produce amino acids. These amino acids should be quickly excreted to the cytosol under nutrient starvation condition and recycled for de novo protein synthesis. These suggest that specific machineries that transport amino acids into and out of the vacuoles operate at the vacuolar membrane. Several families of transporter involved in the vacuolar compartmentalization of amino acids have been identified and characterized using budding yeast Saccharomyces cerevisiae. In this review, we describe the vacuolar amino acid transporters identified so far and introduce recent findings on their activity and physiological function.