Gpr149 is involved in energy homeostasis in the male mouse.

GPR149 is an orphan receptor about which little is known. Accordingly, in the present study, we mapped the tissue expression of Gpr149 in mice using three complementary approaches: quantitative PCR, in situ hybridization, and a newly generated Gpr149-Cre reporter mouse model. The strongest expressions of Gpr149 were observed in neurons of the islands of Calleja, the ventromedial hypothalamus, and the rostral interpeduncular nucleus. Moderate-to-low expression was also observed in the basal forebrain, striatum, hypothalamus, brainstem, and spinal cord. Some Gpr149 expression was also detected in the primary afferent neurons, enteric neurons, and pituitary endocrine cells. This expression pattern is consistent with the involvement of GPR149 signaling in the regulation of energy balance. To explore the physiological function of GPR149 in vivo, we used CRISPR-Cas9 to generate a global knockout allele with mice lacking Gpr149 exon 1. Preliminary metabolic findings indicated that Gpr149-/- mice partially resist weight gain when fed with a high-fat diet and have greater sensitivity to insulin than control mice. In summary, our data may serve as a resource for future in vivo studies on GPR149 in the context of diet-induced obesity.

Human genetic adaptation related to cellular zinc homeostasis.

SLC30A9 encodes a ubiquitously zinc transporter (ZnT9) and has been consistently suggested as a candidate for positive selection in humans. However, no direct adaptive molecular phenotype has been demonstrated. Our results provide evidence for directional selection operating in two major complementary haplotypes in Africa and East Asia. These haplotypes are associated with differential gene expression but also differ in the Met50Val substitution (rs1047626) in ZnT9, which we show is found in homozygosis in the Denisovan genome and displays accompanying signatures suggestive of archaic introgression. Although we found no significant differences in systemic zinc content between individuals with different rs1047626 genotypes, we demonstrate that the expression of the derived isoform (ZnT9 50Val) in HEK293 cells shows a gain of function when compared with the ancestral (ZnT9 50Met) variant. Notably, the ZnT9 50Val variant was found associated with differences in zinc handling by the mitochondria and endoplasmic reticulum, with an impact on mitochondrial metabolism. Given the essential role of the mitochondria in skeletal muscle and since the derived allele at rs1047626 is known to be associated with greater susceptibility to several neuropsychiatric traits, we propose that adaptation to cold may have driven this selection event, while also impacting predisposition to neuropsychiatric disorders in modern humans.

A Treg-specific long noncoding RNA maintains immune-metabolic homeostasis in aging liver.

Regulatory T (Treg) cells modulate several aging-related liver diseases. However, the molecular mechanisms regulating Treg function in this context are unknown. Here we identified a long noncoding RNA, Altre (aging liver Treg-expressed non-protein-coding RNA), which was specifically expressed in the nucleus of Treg cells and increased with aging. Treg-specific deletion of Altre did not affect Treg homeostasis and function in young mice but caused Treg metabolic dysfunction, inflammatory liver microenvironment, liver fibrosis and liver cancer in aged mice. Depletion of Altre reduced Treg mitochondrial integrity and respiratory capacity, and induced reactive oxygen species accumulation, thus increasing intrahepatic Treg apoptosis in aged mice. Moreover, lipidomic analysis identified a specific lipid species driving Treg aging and apoptosis in the aging liver microenvironment. Mechanistically, Altre interacts with Yin Yang 1 to orchestrate its occupation on chromatin, thereby regulating the expression of a group of mitochondrial genes, and maintaining optimal mitochondrial function and Treg fitness in the liver of aged mice. In conclusion, the Treg-specific nuclear long noncoding RNA Altre maintains the immune-metabolic homeostasis of the aged liver through Yin Yang 1-regulated optimal mitochondrial function and the Treg-sustained liver immune microenvironment. Thus, Altre is a potential therapeutic target for the treatment of liver diseases affecting older adults.

l-Type amino acid transporter 1 in hypothalamic neurons in mice maintains energy and bone homeostasis.

Hypothalamic neurons regulate body homeostasis by sensing and integrating changes in the levels of key hormones and primary nutrients (amino acids, glucose, and lipids). However, the molecular mechanisms that enable hypothalamic neurons to detect primary nutrients remain elusive. Here, we identified l-type amino acid transporter 1 (LAT1) in hypothalamic leptin receptor-expressing (LepR-expressing) neurons as being important for systemic energy and bone homeostasis. We observed LAT1-dependent amino acid uptake in the hypothalamus, which was compromised in a mouse model of obesity and diabetes. Mice lacking LAT1 (encoded by solute carrier transporter 7a5, Slc7a5) in LepR-expressing neurons exhibited obesity-related phenotypes and higher bone mass. Slc7a5 deficiency caused sympathetic dysfunction and leptin insensitivity in LepR-expressing neurons before obesity onset. Importantly, restoring Slc7a5 expression selectively in LepR-expressing ventromedial hypothalamus neurons rescued energy and bone homeostasis in mice deficient for Slc7a5 in LepR-expressing cells. Mechanistic target of rapamycin complex-1 (mTORC1) was found to be a crucial mediator of LAT1-dependent regulation of energy and bone homeostasis. These results suggest that the LAT1/mTORC1 axis in LepR-expressing neurons controls energy and bone homeostasis by fine-tuning sympathetic outflow, thus providing in vivo evidence of the implications of amino acid sensing by hypothalamic neurons in body homeostasis.

INDETERMINATE1 autonomously regulates phosphate homeostasis upstream of the miR399-ZmPHO2 signaling module in maize.

The macronutrient phosphorus is essential for plant growth and development. Plants have evolved multiple strategies to increase the efficiency of phosphate (Pi) acquisition to protect themselves from Pi starvation. However, the crosstalk between Pi homeostasis and plant development remains to be explored. Here, we report that overexpressing microRNA399 (miR399) in maize (Zea mays) is associated with premature senescence after pollination. Knockout of ZmPHO2 (Phosphate 2), a miR399 target, resulted in a similar premature senescence phenotype. Strikingly, we discovered that INDETERMINATE1 (ID1), a floral transition regulator, inhibits the transcription of ZmMIR399 genes by directly binding to their promoters, alleviating the repression of ZmPHO2 by miR399 and ultimately contributing to the maintenance of Pi homeostasis in maize. Unlike ZmMIR399 genes, whose expression is induced by Pi deficiency, ID1 expression was independent of the external inorganic orthophosphate status, indicating that ID1 is an autonomous regulator of Pi homeostasis. Furthermore, we show that ZmPHO2 was under selection during maize domestication and cultivation, resulting in a more sensitive response to Pi starvation in temperate maize than in tropical maize. Our study reveals a direct functional link between Pi-deprivation sensing by the miR399-ZmPHO2 regulatory module and plant developmental regulation by ID1.

Ether lipid deficiency disrupts lipid homeostasis leading to ferroptosis sensitivity.

Ferroptosis is an iron-dependent form of regulated cell death associated with uncontrolled membrane lipid peroxidation and destruction. Previously, we showed that dietary dihomo-gamma-linolenic acid (DGLA; 20: 3(n-6)) triggers ferroptosis in the germ cells of the model organism, Caenorhabditis elegans. We also demonstrated that ether lipid-deficient mutant strains are sensitive to DGLA-induced ferroptosis, suggesting a protective role for ether lipids. The vinyl ether bond unique to plasmalogen lipids has been hypothesized to function as an antioxidant, but this has not been tested in animal models. In this study, we used C. elegans mutants to test the hypothesis that the vinyl ether bond in plasmalogens acts as an antioxidant to protect against germ cell ferroptosis as well as to protect from whole-body tert-butyl hydroperoxide (TBHP)-induced oxidative stress. We found no role for plasmalogens in either process. Instead, we demonstrate that ether lipid-deficiency disrupts lipid homeostasis in C. elegans, leading to altered ratios of saturated and monounsaturated fatty acid (MUFA) content in cellular membranes. We demonstrate that ferroptosis sensitivity in both wild type and ether-lipid deficient mutants can be rescued in several ways that change the relative abundance of saturated fats, MUFAs and specific polyunsaturated fatty acids (PUFAs). Specifically, we reduced ferroptosis sensitivity by (1) using mutant strains unable to synthesize DGLA, (2) using a strain carrying a gain-of-function mutation in the transcriptional mediator MDT-15, or (3) by dietary supplementation of MUFAs. Furthermore, our studies reveal important differences in how dietary lipids influence germ cell ferroptosis versus whole-body peroxide-induced oxidative stress. These studies highlight a potentially beneficial role for endogenous and dietary MUFAs in the prevention of ferroptosis.

Homeostasis Imbalance of YY2 and YY1 Promotes Tumor Growth by Manipulating Ferroptosis.

Ferroptosis is a type of programmed cell death caused by disruption of redox homeostasis and is closely linked to amino acid metabolism. Yin Yang 2 (YY2) and its homolog Yin Yang 1 (YY1) are highly homologous, especially in their zinc-finger domains. Furthermore, they share a consensus DNA binding motif. Increasing evidences have demonstrated the tumor suppressive effect of YY2, in contrast with the oncogenic YY1; however, little is known about the biological and pathological functions of YY2. Here, it is determined that YY2 induces tumor cell ferroptosis and subsequently suppresses tumorigenesis by inhibiting solute carrier family 7 member 11 (SLC7A11) transcription, leading to the decreased glutathione biosynthesis. Furthermore, YY2 and YY1 bind competitively to the same DNA binding site in the SLC7A11 promoter and antagonistically regulate tumor cell ferroptosis, thus suggesting the molecular mechanism underlying their opposite regulation on tumorigenesis. Moreover, mutations of YY2 zinc-finger domains in clinical cancer patients abrogate YY2/SLC7A11 axis and tumor cell ferroptosis. Together, these results provide a new insight regarding the regulatory mechanism of ferroptosis, and a mechanistic explanation regarding the tumor suppressive effect of YY2. Finally, these findings demonstrate that homeostasis between YY1 and YY2 is crucial for maintaining redox homeostasis in tumor cells.

Two NPF transporters mediate iron long-distance transport and homeostasis in Arabidopsis.

Iron (Fe) transport and reallocation are essential to Fe homeostasis in plants, but it is unclear how Fe homeostasis is regulated, especially under stress. Here we report that NPF5.9 and its close homolog NPF5.8 redundantly regulate Fe transport and reallocation in Arabidopsis. NPF5.9 is highly upregulated in response to Fe deficiency. NPF5.9 expresses preferentially in vasculature tissues and localizes to the trans-Golgi network, and NPF5.8 showed a similar expression pattern. Long-distance Fe transport and allocation into aerial parts was significantly increased in NPF5.9-overexpressing lines. In the double mutant npf5.8 npf5.9, Fe loading in aerial parts and plant growth were decreased, which were partially rescued by Fe supplementation. Further analysis showed that expression of PYE, the negative regulator for Fe homeostasis, and its downstream target NAS4 were significantly altered in the double mutant. NPF5.9 and NPF5.8 were shown to also mediate nitrate uptake and transport, although nitrate and Fe application did not reciprocally affect each other. Our findings uncovered the novel function of NPF5.9 and NPF5.8 in long-distance Fe transport and homeostasis, and further indicated that they possibly mediate nitrate transport and Fe homeostasis independently in Arabidopsis.

Crabp1 Modulates HPA Axis Homeostasis and Anxiety-like Behaviors by Altering FKBP5 Expression.

Retinoic acid (RA), the principal active metabolite of vitamin A, is known to be involved in stress-related disorders. However, its mechanism of action in this regard remains unclear. This study reports that, in mice, endogenous cellular RA binding protein 1 (Crabp1) is highly expressed in the hypothalamus and pituitary glands. Crabp1 knockout (CKO) mice exhibit reduced anxiety-like behaviors accompanied by a lowered stress induced-corticosterone level. Furthermore, CRH/DEX tests show an increased sensitivity (hypersensitivity) of their feedback inhibition in the hypothalamic-pituitary-adrenal (HPA) axis. Gene expression studies show reduced FKBP5 expression in CKO mice; this would decrease the suppression of glucocorticoid receptor (GR) signaling thereby enhancing their feedback inhibition, consistent with their dampened corticosterone level and anxiety-like behaviors upon stress induction. In AtT20, a pituitary gland adenoma cell line elevating or reducing Crabp1 level correspondingly increases or decreases FKBP5 expression, and its endogenous Crabp1 level is elevated by GR agonist dexamethasone or RA treatment. This study shows, for the first time, that Crabp1 regulates feedback inhibition of the the HPA axis by modulating FKBP5 expression. Furthermore, RA and stress can increase Crabp1 level, which would up-regulate FKBP5 thereby de-sensitizing feedback inhibition of HPA axis (by decreasing GR signaling) and increasing the risk of stress-related disorders.

OsWRKY108 is an integrative regulator of phosphorus homeostasis and leaf inclination in rice.

Phosphorus (P), which is taken up by plants as inorganic phosphate (Pi), is one of the most important macronutrients for plant growth and development. Meanwhile, it determines plant architecture in several ways, including leaf inclination. However, the molecular basis underlying the crosstalk between the signaling pathways of plant P homeostasis and architecture maintenance remains elusive. We recently characterized a WRKY transcription factor, OsWRKY108, in rice (Oryza sativa). It functions redundantly with OsWRKY21 to promote Pi uptake in response to Pi supply. Overexpression of either OsWRKY108 or OsWRKY21 led to up-regulation of Pi transporter genes and thus enhanced Pi accumulation. By contrast, transgenic rice plants expressing OsWRKY21-SRDX (a fusion protein transforming OsWRKY21 from an activator into a dominant repressor) but not the OsWRKY108-SRDX fusion showed decreased Pi accumulation under Pi-replete conditions. Here, we report that OsWRKY108 acts as a positive regulator of leaf inclination. OsWRKY108 overexpressors showed increased leaf inclination and OsWRKY108-SRDX plants showed an erect-leaf phenotype, irrespective of the Pi regimes. Nevertheless, the response of leaf inclination to Pi starvation was largely impaired upon OsWRKY108 overexpression. Moreover, in both OsWRKY108-SRDX plants and OsWRKY108 overexpressors, the 'percentage of leaf angle alteration relative to wild-type' under Pi-starvation condition was more significant than that under Pi-replete condition. These results suggest that the regulation of OsWRKY108 on leaf inclination is in part dependent on Pi availability. Altogether, our findings demonstrate that OsWRKY108 is an integrative regulator of P homeostasis and leaf inclination, serving as a link between plant nutrient signaling and developmental cues.

Central 5-HTR2C in the Control of Metabolic Homeostasis.

The 5-hydroxytryptamine 2C receptor (5-HTR2C) is a class G protein-coupled receptor (GPCR) enriched in the hypothalamus and the brain stem, where it has been shown to regulate energy homeostasis, including feeding and glucose metabolism. Accordingly, 5-HTR2C has been the target of several anti-obesity drugs, though the associated side effects greatly curbed their clinical applications. Dissecting the specific neural circuits of 5-HTR2C-expressing neurons and the detailed molecular pathways of 5-HTR2C signaling in metabolic regulation will help to develop better therapeutic strategies towards metabolic disorders. In this review, we introduced the regulatory role of 5-HTR2C in feeding behavior and glucose metabolism, with particular focus on the molecular pathways, neural network, and its interaction with other metabolic hormones, such as leptin, ghrelin, insulin, and estrogens. Moreover, the latest progress in the clinical research on 5-HTR2C agonists was also discussed.

Interleukin-6 promotes ferroptosis in bronchial epithelial cells by inducing reactive oxygen species-dependent lipid peroxidation and disrupting iron homeostasis.

Asthma occurs accompanied by the ferroptosis in bronchial epithelial cells, during which Interleukin-6 (IL-6) plays a key role. However, the associations between IL-6, ferroptosis and asthma have not been reported. Bronchial epithelial cells BEAS-2B cells were induced by different concentrations of IL-6 and cell viability was detected by MTT assay. The TBARS production rate was detected by corresponding kit. The expression of oxidative stress-related indexes was detected by ELISA. The Iron Assay Kits detected total iron levels and ferrous ion (Fe2+) levels. Labile iron pool assay was used to detect the cell unstable iron pool. The expression of ferroptosis-related proteins was detected by Western blot. To further examine the mechanism of action, ferroptosis inhibitor Ferrostatin 1 (Fer-1), antioxidant NAC, and the iron supplement Fe were added. We found that IL-6 decreased the activity, promoted lipid peroxidation, disrupted iron homeostasis of BEAS-2B cells, and induced iron death in bronchial epithelial BEAS-2B cells. However, pretreatment with Ferrostatin-1 (Fer-1) and antioxidant NAC partially reversed the effect of IL-6 on lipid peroxidation and ferroptosis in BEAS-2B cells, while Fe augmented the effect. Overall, IL-6 promotes ferroptosis in bronchial epithelial cells by inducing reactive oxygen species (ROS)-dependent lipid peroxidation and disrupting iron homeostasis.

Selenium-GPX4 axis protects follicular helper T cells from ferroptosis.

Follicular helper T (TFH) cells are a specialized subset of CD4+ T cells that essentially support germinal center responses where high-affinity and long-lived humoral immunity is generated. The regulation of TFH cell survival remains unclear. Here we report that TFH cells show intensified lipid peroxidation and altered mitochondrial morphology, resembling the features of ferroptosis, a form of programmed cell death that is driven by iron-dependent accumulation of lipid peroxidation. Glutathione peroxidase 4 (GPX4) is the major lipid peroxidation scavenger and is necessary for TFH cell survival. The deletion of GPX4 in T cells selectively abrogated TFH cells and germinal center responses in immunized mice. Selenium supplementation enhanced GPX4 expression in T cells, increased TFH cell numbers and promoted antibody responses in immunized mice and young adults after influenza vaccination. Our findings reveal the central role of the selenium-GPX4-ferroptosis axis in regulating TFH homeostasis, which can be targeted to enhance TFH cell function in infection and following vaccination.

SIRT1-dependent restoration of NAD+ homeostasis after increased extracellular NAD+ exposure.

In the last several years, NAD+ supplementation has emerged as an innovative and safe therapeutic strategy for a wide spectrum of disorders, including diabetes and neuropathy. However, critical questions remain as to how NAD+ and its precursors are taken up by cells, as well as the effects of long-lasting intracellular NAD+ (iNAD+) increases. Here, we investigated the kinetics of iNAD+ levels in different cell types challenged with prolonged exposure to extracellular NAD+ (eNAD+). Surprisingly, we found that after the initial increase, iNAD+ contents decreased back to control levels (iNAD+ resetting). Focusing our attention on HeLa cells, we found that oxygen and ATP consumption occurred with similar temporal kinetics after eNAD+ exposure. Using [3H]NAD+ and [14C]NAD+, we determined that NAD+ resetting was not due to increased dinucleotide extrusion but rather due to reduced uptake of cleaved NAD+ products. Indeed, eNAD+ exposure reduced the expression of the ecto-5'-nucleotidase CD73, the nicotinamide adenine mononucleotide transporter solute carrier family 12 member 8, and the nicotinamide riboside kinase. Interestingly, silencing the NAD+-sensor enzyme sirtuin 1 prevented eNAD+-dependent transcriptional repression of ecto-5'-nucleotidase, solute carrier family 12 member 8, and nicotinamide riboside kinase, as well as iNAD+ resetting. Our findings provide the first evidence for a sirtuin 1-mediated homeostatic response aimed at maintaining physiological iNAD+ levels in conditions of excess eNAD+ availability. These data may be of relevance for therapies designed to support the NAD+ metabolome via extracellular supplementation of the dinucleotide or its precursors.

Upregulation of Vitamin C Transporter Functional Expression in 5xFAD Mouse Intestine.

The process of obtaining ascorbic acid (AA) via intestinal absorption and blood circulation is carrier-mediated utilizing the AA transporters SVCT1 and SVCT2, which are expressed in the intestine and brain (SVCT2 in abundance). AA concentration is decreased in Alzheimer's disease (AD), but information regarding the status of intestinal AA uptake in the AD is still lacking. We aimed here to understand how AA homeostasis is modulated in a transgenic mouse model (5xFAD) of AD. AA levels in serum from 5xFAD mice were markedly lower than controls. Expression of oxidative stress response genes (glutathione peroxidase 1 (GPX1) and superoxide dismutase 1 (SOD1)) were significantly increased in AD mice jejunum, and this increase was mitigated by AA supplementation. Uptake of AA in the jejunum was upregulated. This increased AA transport was caused by a marked increase in SVCT1 and SVCT2 protein, mRNA, and heterogeneous nuclear RNA (hnRNA) expression. A significant increase in the expression of HNF1α and specific protein 1 (Sp1), which drive SLC23A1 and SLC23A2 promoter activity, respectively, was observed. Expression of hSVCT interacting proteins GRHPR and CLSTN3 were also increased. SVCT2 protein and mRNA expression in the hippocampus of 5xFAD mice was not altered. Together, these investigations reveal adaptive up-regulation of intestinal AA uptake in the 5xFAD mouse model.

Nutritive Manganese and Zinc Overdosing in Aging C. elegans Result in a Metallothionein-Mediated Alteration in Metal Homeostasis.

SCOPE: Manganese (Mn) and zinc (Zn) are not only essential trace elements, but also potential exogenous risk factors for various diseases. Since the disturbed homeostasis of single metals can result in detrimental health effects, concerns have emerged regarding the consequences of excessive exposures to multiple metals, either via nutritional supplementation or parenteral nutrition. This study focuses on Mn-Zn-interactions in the nematode Caenorhabditis elegans (C. elegans) model, taking into account aspects related to aging and age-dependent neurodegeneration. METHODS AND RESULTS: Chronic co-exposure of C. elegans to Mn and Zn increases metal uptake, exceeding levels of single metal exposures. Supplementation with Mn and/or Zn also leads to an age-dependent increase in metal content, a decline in overall mRNA expression, and metal co-supplementation induced expression of target genes involved in Mn and Zn homeostasis, in particular metallothionein 1 (mtl-1). Studies in transgenic worms reveal that mtl-1 played a prominent role in mediating age- and diet-dependent alterations in metal homeostasis. Metal dyshomeostasis is further induced in parkin-deficient nematodes (Parkinson's disease (PD) model), but this did not accelerate the age-dependent dopaminergic neurodegeneration. CONCLUSIONS: A nutritive overdose of Mn and Zn can alter interactions between essential metals in an aging organism, and metallothionein 1 acts as a potential protective modulator in regulating homeostasis.

FIT and bHLH Ib transcription factors modulate iron and copper crosstalk in Arabidopsis.

Although the crosstalk between iron (Fe) and copper (Cu) homeostasis signalling networks exists in plants, the underlined molecular mechanism remains unclear. FIT (FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR) and four bHLH Ib members (bHLH38, bHLH39, bHLH100 and bHLH101) are the key regulators of Fe homeostasis. Here, we reveal that FIT and bHLH Ib control the up-regulation of Cu-uptake genes (COPT2, FRO4 and FRO5) by Fe deficiency, and Cu is required for improving plant growth under Fe-deficiency conditions. The induction of Cu-uptake gene expression and the elevation of Cu concentration are inhibited in the fit-2 or bhlh4x (the quadruple mutant of four bHLH Ib genes) under Fe-deficiency conditions. The dual overexpression of both bHLH38 (or bHLH39) and FIT activates the expression of COPT2, FRO4 and FRO5 and increases Cu accumulation. Furthermore, bHLH Ib proteins directly bind to the promoters of COPT2, FRO4 and FRO5. Either Cu supplement or overexpression of COPT2 or FRO4 improves the growth of fit-2 under Fe-deficiency conditions. Moreover, the induction of COPT2, FRO4 and FRO5 by Fe deficiency is independent of SPL7, a central regulator of Cu-deficiency responses. This work through the link between bHLH Ib/FIT and COPT2/FRO4/FRO5 under Fe-deficiency conditions establishes a new relationship between Cu and Fe homeostasis.

Ammonium Accumulation Caused by Reduced Tonoplast V-ATPase Activity in Arabidopsis thaliana.

Plant vacuoles are unique compartments that play a critical role in plant growth and development. The vacuolar H+-ATPase (V-ATPase), together with the vacuolar H+-pyrophosphatase (V-PPase), generates the proton motive force that regulates multiple cell functions and impacts all aspects of plant life. We investigated the effect of V-ATPase activity in the vacuole on plant growth and development. We used an Arabidopsisthaliana (L.) Heynh. double mutant, vha-a2 vha-a3, which lacks two tonoplast-localized isoforms of the membrane-integral V-ATPase subunit VHA-a. The mutant is viable but exhibits impaired growth and leaf chlorosis. Nitrate assimilation led to excessive ammonium accumulation in the shoot and lower nitrogen uptake, which exacerbated growth retardation of vha-a2 vha-a3. Ion homeostasis was disturbed in plants with missing VHA-a2 and VHA-a3 genes, which might be related to limited growth. The reduced growth and excessive ammonium accumulation of the double mutant was alleviated by potassium supplementation. Our results demonstrate that plants lacking the two tonoplast-localized subunits of V-ATPase can be viable, although with defective growth caused by multiple factors, which can be alleviated by adding potassium. This study provided a new insight into the relationship between V-ATPase, growth, and ammonium accumulation, and revealed the role of potassium in mitigating ammonium toxicity.

Isolation and Characterization of Three Sodium-Phosphate Cotransporter Genes and Their Transcriptional Regulation in the Grass Carp Ctenopharyngodon idella.

It is important to explore the regulatory mechanism of phosphorus homeostasis in fish, which help avoid the risk of P toxicity and prevent P pollution in aquatic environment. The present study obtained the full-length cDNA sequences and the promoters of three SLC20 members (slc20a1a, slc20a1b and slc20a2) from grass carp Ctenopharyngodon idella, and explored their responses to inorganic phosphorus (Pi). Grass carp SLC20s proteins possessed conservative domains and amino acid sites relevant with phosphorus transport. The mRNAs of three slc20s appeared in the nine tissues, but their expression levels were tissue-dependent. The binding sites of three transcription factors (SREBP1, NRF2 and VDR) were predicted on the slc20s promoters. The mutation and EMSA analysis indicated that: (1) SREBP1 binding site (-783/-771 bp) negatively but VDR (-260/-253 bp) binding site positively regulated the activities of slc20a1a promoter; (2) SREBP1 (-1187/-1178 bp), NRF2 (-572/-561 bp) and VDR(615/-609 bp) binding sites positively regulated the activities of slc20a1b promoter; (3) SREBP1 (-987/-977 bp), NRF2 (-1469/-1459 bp) and VDR (-1124/-1117 bp) binding sites positively regulated the activities of the slc20a2 promoter. Moreover, Pi incubation significantly reduced the activities of three slc20s promoters, and Pi-induced transcriptional inactivation of slc20s promoters abolished after the mutation of the VDR element but not SREBP1 and NRF2 elements. Pi incubation down-regulated the mRNA levels of three slc20s. For the first time, our study elucidated the transcriptional regulatory mechanisms of SLC20s and their responses to Pi, which offered new insights into the Pi homeostatic regulation and provided the basis for reducing phosphorus discharge into the waters.

Physical Activity-Dependent Regulation of Parathyroid Hormone and Calcium-Phosphorous Metabolism.

Exercise perturbs homeostasis, alters the levels of circulating mediators and hormones, and increases the demand by skeletal muscles and other vital organs for energy substrates. Exercise also affects bone and mineral metabolism, particularly calcium and phosphate, both of which are essential for muscle contraction, neuromuscular signaling, biosynthesis of adenosine triphosphate (ATP), and other energy substrates. Parathyroid hormone (PTH) is involved in the regulation of calcium and phosphate homeostasis. Understanding the effects of exercise on PTH secretion is fundamental for appreciating how the body adapts to exercise. Altered PTH metabolism underlies hyperparathyroidism and hypoparathyroidism, the complications of which affect the organs involved in calcium and phosphorous metabolism (bone and kidney) and other body systems as well. Exercise affects PTH expression and secretion by altering the circulating levels of calcium and phosphate. In turn, PTH responds directly to exercise and exercise-induced myokines. Here, we review the main concepts of the regulation of PTH expression and secretion under physiological conditions, in acute and chronic exercise, and in relation to PTH-related disorders.