Calcium Uptake Research Articles

Does a hormonal plant growth promoter (KIN, GA3, and IBA) affect grain yield and N, P, K, Ca, and Mg uptake in wheat crop in Southern Brazil?

Plant growth-promoting substances have been commercialized in agriculture, especially synthetic hormones such as kinetin (KIN), gibberellic acid (GA3), and indole-3-butyric acid (IBA). However, few studies proved the agronomic effect of these substances on the main crops. The objective of this work was to evaluate rates and methods of application of a hormonal plant growth promoter (HPGP −0.09 g L−1 KIN, 0.05 g L−1 GA3, and 0.05 g L−1 IBA) and their effects on wheat grain yield and nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) uptake. The research was carried out in Londrina, Brazil. A randomized block design was implemented, considering a 2 × 3 × 4 factorial arrangement. It was composed of two genotypes (BRS Gralha–Azul and BRS Sanhaço), three HPGP rates (0, 5, and 10 mL kg−1) applied on the seeds, and four HPGP rates (0, 0.25, 0.5, and 1 L ha−1) sprayed on the leaves. Applications of HPGP did not change grain yield, density of fertile plants, lodging, plant height, aboveground dry matter (AGDM); P, Ca, and Mg concentration in the AGDM; and P, K, Ca, and Mg utilization efficiency (UE). In 2016, the application of 5 mL kg−1 HPGP on the seeds (without HPGP on the leaves) increased by 20.9% the N concentration in the AGDM. In 2017, NUE increased up to 21.2% in response to HPGP sprayed on the leaves. The diversity of interactions among genotypes, HPGP application techniques, and weather conditions hinders the assertive use of the product by farmers.

Effects of Elemental Sulfur on Soil pH and Growth of Saskatoon Berry (Amelanchier alnifolia) and Beaked Hazelnut (Corylus cornuta) Seedlings

The land disturbed by open-pit oil sands mining must be restored to support the survival and growth of native boreal plants. Because tailings sand and sodic shale overburden are commonly used as an underlying parent substrate that is capped by boreal forest cover soils, the soil pH in reclamation sites is often higher compared with undisturbed boreal forest soil. Sulfur is a major byproduct of oil sands refining and could potentially be used as an amendment to lower the soil pH on reclamation sites. In this study, we examined the effects of soil pH and elemental sulfur on growth and physiological responses in Saskatoon berry and beaked hazelnut seedlings. We found that elemental sulfur was effective in lowering soil pH. However, addition of elemental sulfur to a forest soil of pH 5.7 lowered the soil pH to around 3, which impaired the growth and physiological performance of both plant species. The addition of 5 and 25 g kg−1 elemental sulfur to the pH 8.5 soil did not substantially improve the examined growth and physiological parameters in Saskatoon berry and beaked hazelnut seedlings. Further, excess addition of elemental sulfur in high pH soil could reduce the uptake of nitrogen, phosphorus, and calcium in Saskatoon berry. The results demonstrate that the amount of sulfur applied to the soil would need to be carefully determined for different soil types and pH levels to avoid potential toxicity effects.

Discovery of calcium-binding peptides derived from defatted lemon basil seeds with enhanced calcium uptake in human intestinal epithelial cells, Caco-2

It is anticipated that calcium-chelating peptides may serve to enhance the absorption of calcium. This research examined defatted lemon basil seeds (DLBS) which had been treated with Alcalase under optimized parameters for the degree of hydrolysis for proteolysis, discovering that the activity for calcium-binding in a competitive condition with phosphate ion was 60.39 ± 1.545%. The purification of the hydrolysates was performed via ultrafiltration along with reversed-phase high performance liquid chromatography (RP-HPLC). Determination of the purified peptide amino acid sequence was confirmed for both peptides and reported as Ala-Phe-Asn-Arg-Ala-Lys-Ser-Lys-Ala-Leu-Asn-Glu-Asn (AFNRAKSKALNEN; Basil-1), and Tyr-Asp-Ser-Ser-Gly-Gly-Pro-Thr-Pro-Trp-Leu-Ser-Pro-Tyr (YDSSGGPTPWLSPY; Basil-2). The respective activities for calcium-binding were 38.62 ± 1.33%, and 42.19 ± 2.27%. Fluorescence spectroscopy, and fourier transform infrared spectroscopy were employed in order to assess the chelating mechanism between calcium and the peptides. It was found that the calcium ions took place through the activity of the amino nitrogen atoms and the oxygen atoms on the carboxyl group. Moreover, both of these peptides served to improve calcium transport and absorption in Caco-2 cell monolayers, depending on the concentration involved. It was revealed that the peptide-calcium complexes offered an increased calcium absorption percentage when compared to free calcium at similar concentrations. It might be concluded that the peptide within the peptide-calcium complex can promote calcium absorption through both active and passive transport pathways by increasing calcium concentration and promoting cell membrane interaction. Accordingly, DLBS protein can be considered a strong potential source of protein which can be used to produce calcium-binding peptides and might therefore play a role in the production of nutraceutical foods as a bioactive ingredient.

Structures of PKA-phospholamban complexes reveal a mechanism of familial dilated cardiomyopathy.

Several mutations identified in phospholamban (PLN) have been linked to familial dilated cardiomyopathy (DCM) and heart failure, yet the underlying molecular mechanism remains controversial. PLN interacts with sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) and regulates calcium uptake, which is modulated by the protein kinase A (PKA)-dependent phosphorylation of PLN during the fight-or-flight response. Here, we present the crystal structures of the catalytic domain of mouse PKA in complex with wild-type and DCM-mutant PLNs. Our structures, combined with the results from other biophysical and biochemical assays, reveal a common disease mechanism: the mutations in PLN reduce its phosphorylation level by changing its conformation and weakening its interactions with PKA. In addition, we demonstrate that another more ubiquitous SERCA-regulatory peptide, called another-regulin (ALN), shares a similar mechanism mediated by PKA in regulating SERCA activity.

MCU-dependent mitochondrial calcium uptake-induced mitophagy contributes to apelin-13-stimulated VSMCs proliferation

Apelin is an endogenous ligand of the G protein-coupled receptor APJ. Both apelin and APJ receptors, which are expressed in vascular smooth muscle cells (VSMCs), play important roles in the cardiovascular system. Our previous studies researches indicated that mitophagy mediated apelin-13-induced VSMCs proliferation. However, little is known about how apelin-13 regulates mitophagy to participate in VSMC proliferation. The results of the present study demonstrated that mitochondrial calcium uniporter (MCU) uptake-dependent mitochondrial calcium-induced mitophagy is involved in apelin-13-induced VSMCs proliferation. Apelin-13 promoted the expression of MCU which increases mitochondrial calcium uptake. Apelin-13-induced MCU-dependent mitochondrial calcium uptake further increased mitochondrial ROS (mtROS) concentrations and promoted mitophagy, which can be evidenced through the upregulation of the Dynamin-related protein 1(Drp1), PTEN-induced kinase 1 (PINK1), and Parkin. The clearance of mtROS by Mito-TEMPO significantly reversed apelin-13-induced mitophagy. Moreover, both the Drp1 inhibitor mdivi-1 and siRNA-Drp1 inhibited apelin-13-induced mitophagy. Furthermore, the APJ receptor antagonist F13A, MCU inhibitor Ru360, mitochondria-targeted antioxidant Mito-TEMPO, Drp1 inhibitor Mdivi-1, siRNA-Drp1, siRNA-PINK1, and siRNA-Parkin inhibited the proliferation of VSMCs induced by apelin-13. In ApoE−/− mice, intraperitoneal administration of apelin-13 induced the expression of MCU, Drp1, PINK1, Parkin, and α-SMA and increased atherosclerotic plaque lesions. However, F13A and Ru360 decreased the expression of MCU, Drp1, PINK1, Parkin, and α-SMA and reduced atherosclerotic plaque lesions in ApoE−/− mice injected with apelin-13. Collectively, our results demonstrate that MCU-dependent mitochondrial calcium uptake-induced mitophagy is involved in apelin-13-stimulated VSMCs proliferation.

Evaluation of integrated ultrasound and CaCl2 in hydrocooling water on the quality of ‘Bing’, ‘Lapins’, and ‘Sweetheart’ cherries stored in modified atmosphere packaging

Sweet cherry is a highly perishable fruit with a short storage life. Although CaCl2 dips positively affect the quality of sweet cherries, traditional sanitizer (i.e. NaClO) in the cleaning step contributes to fruit oxidation. The primary purpose of this study was to evaluate whether integrated applications of a chemical-free sanitizing technology (ultrasound) and CaCl2 in hydrocooling water (0 °C) had the potential in improving the quality of ‘Bing’, ‘Lapins’, and ‘Sweetheart’ cherries either packing in polyethylene (PE) or modified atmosphere packaging (MAP) bags. Regardless of cultivar and packaging type, ultrasound showed a similar effect as NaClO on quality attributes, decay, and antioxidant compounds (i.e. DPPH free radicals scavenging capacity, ferric reducing antioxidant power (FRAP), total phenolics (TP), and total flavonoids (TF)). However, NaClO induced high rates of stem browning (SB) and pitting in ‘Bing’ and ‘Lapins’ cherries packed with PE and MAP bags. Fortunately, Ultrasound + MAP provided a greater benefit in reducing SB in ‘Bing’ cherries. Adding 22.5–90 mM CaCl2 to hydrocooling water effectively enhanced calcium (Ca) and chloride (Cl) uptake in ‘Bing’ and ‘Lapins’, but not in ‘Sweetheart’. The cubic model showed high correlations between applied CaCl2 concentrations and postharvest disorders. Furthermore, CaCl2 concentration at 22.5–45 mM had stronger effects on reducing pitting and retaining TP in all three cultivars, irrespective of packaging type. However, increasing the application of CaCl2 concentration to 90 mM caused salt injury. Ultrasound did not provide an additional effect in increasing Ca and Cl uptake when it was combined with 22.5 mM CaCl2. However, this combination treatment retained high FF and SPF in all three cultivars packed with PE or MAP bags. Additionally, CaCl2 + ultrasound + MAP further reduced decay incidence in ‘Bing’ and ‘Lapins’ cherries and maintained high TP in ‘Lapins’ and ‘Sweetheart’ cherries, compared to the CaCl2 + ultrasound + PE treatment. Overall, the ultrasound with 22.5 mM CaCl2 in hydrocooling water slowed down quality deterioration, delayed disorders development, and improved antioxidant metabolism in MAP cherries.

Exosomal miR-181a-2-3p derived from citreoviridin-treated hepatocytes activates hepatic stellate cells trough inducing mitochondrial calcium overload

Increasing evidences indicate the vital role of exosomes-mediated intercellular communication in the pathogenesis of liver fibrosis. However, the underlying mechanisms are still not clearly defined. In this study, we found that citreoviridin (CIT), a mycotoxin and ectopic ATP synthase (e-ATPS) inhibitor, induced liver fibrosis in mice. The exosomes derived from CIT-treated L-02 hepatocytes activated hepatic stellate cells (HSC) LX-2. With exosomal small RNA sequencing, we found 156 differentially expressed miRNAs in the exosomes from CIT-treated L-02 cells, and the predicted target genes of exosomal miRNAs were enriched in calcium signaling pathway. The exosomes from CIT-treated L-02 cells induced mitochondrial calcium accumulation in LX-2 cells. And pharmacological inhibition of mitochondrial calcium uptake relieved exosomes-activated fibrogenic response in LX-2 cells. The miR-181a-2-3p that was predicted to target-regulate mitochondrial calcium uptake 1 (MICU1) was significantly increased in the exosomes from CIT-treated L-02 cells. Exosomes-induced reduction of MICU1, mitochondrial calcium overload and activation of LX-2 cells were reversed by AntagomiR-181a-2-3p. In this study, we pointed out that exosomal miR-181a-2-3p from CIT-treated hepatocytes induced mitochondrial calcium accumulation and activated HSC subsequently through inhibiting the expression of MICU1, shedding new light on the mechanism underlying liver fibrosis and CIT hepatotoxicity.

Differential mitochondrial and cellular responses between H vs. J mtDNA haplogroup-containing human RPE transmitochondrial cybrid cells

Mitochondrial dysfunction is associated with several retinal degenerative diseases including Age-related Macular Degeneration (AMD). Human mitochondrial DNA (mtDNA) haplogroups are inherited from a common ancestral clan and are defined by specific sets of genetic differences. The purpose of this study was to determine and compare the effects of mtDNA haplogroups H and J on transcriptome regulation and cellular resilience to oxidative stress in human RPE cytoplasmic hybrid (cybrid) cell lines in vitro.ARPE-19 cybrid cell lines containing mtDNA haplogroups H and J were created by fusing platelets obtained from normal individuals containing H and J haplogroups with mitochondria-deficient (Rho0) ARPE-19 cell lines. These cybrids were exposed to oxidative stress using 300 μM hydrogen peroxide (H2O2), following which mitochondrial structural dynamics was studied at varying time points using the mitochondrial markers - TOMM20 (Translocase of Outer Mitochondrial Membrane 20) and Mitotracker. To evaluate mitochondrial function, levels of ROS, ΔΨm and [Ca2+]m were measured using flow cytometry, and ATP levels were measured using luminescence. The H and J cybrid cell transcriptomes were compared using RNAseq to determine how changes in mtDNA regulate gene expression. Inflammatory and angiogenic markers were measured using Luminex assay to understand how these mtDNAs influenced cellular response to oxidative stress. Actin filaments’ morphology was examined using confocal microscopy.Following exposure to H2O2 stress, the J cybrids showed increased mitochondrial swelling and perinuclear localization, disturbed fission and fusion, increased calcium uptake (p < 0.05), and higher secreted levels of TNF-α and VEGF (p < 0.001), compared to the H cybrids. Calcium uptake by J cybrids was reduced using an IP3R inhibitor. Thirteen genes involved in mitochondrial complex I and V function, fusion/fission events, cellular energy homeostasis, antioxidant defenses, and inflammatory responses, were significantly downregulated with log2 fold changes ranging between −1.5 and −5.1. Actin levels were also significantly reduced in stressed J cybrids (p ≤ 0.001) and disruption in actin filaments was observed. Thirty-eight genes involved in mitochondrial and cellular support functions, were upregulated with log2 fold changes of +1.5 to +5.9 in J cybrids compared to H cybrids.Our results demonstrate significant structural and functional differences between mtDNA haplogroups H vs. J -containing cybrid cells. Our study suggests that the J mtDNA haplogroup can alter the transcriptome to increase cellular susceptibility to stress and retinal degenerations.

Genes and compounds that increase type VII collagen expression as potential treatments for dystrophic epidermolysis bullosa.

Dystrophic epidermolysis bullosa (DEB) is a skin-blistering disease caused by mutations in COL7A1, which encodes type VII collagen (C7). There is no cure for DEB, but previous work has shown potential therapeutic benefit of increased production of even partially functional C7. Genome-wide screens using CRISPR-Cas9 have enabled the identification of genes involved in cancer development, drug resistance and other genetic diseases, suggesting that they could be used to identify drivers of C7 production. A keratinocyte C7 reporter cell line was created and used in a genome-wide CRISPR activation (CRISPRa) screen to identify genes and pathways that increase C7 expression. The CRISPRa screen results were used to develop a targeted drug screen to identify compounds that upregulate C7 expression. The C7_tdTomato cell line was validated as an effective reporter for detection of C7 upregulation. The CRISPRa screen identified DENND4B and TYROBP as top gene hits plus pathways related to calcium uptake and immune signalling in C7 regulation. The targeted drug screen identified several compounds that increase C7 expression in keratinocytes, of which kaempferol, a plant flavonoid, also significantly increased C7mRNA and protein in DEB patient cells.

Hepatocyte growth factor protects pulmonary endothelial barrier against oxidative stress and mitochondria-dependent apoptosis.

Background:Pulmonary microvascular endothelial cells (PMVECs) were not complex, and the endothelial barrier was destroyed in the pathogenesis progress of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Previous studies have demonstrated that hepatocyte growth factor (HGF), which was secreted by bone marrow mesenchymal stem cells, could decrease endothelial apoptosis. We investigated whether mTOR/STAT3 signaling acted in HGF protective effects against oxidative stress and mitochondria-dependent apoptosis in lipopolysaccharide (LPS)-induced endothelial barrier dysfunction and ALI mice.Methods:In our current study, we introduced LPS-induced PMEVCs with HGF treatment. To investigate the effects of mammalian target of rapamycin (mTOR)/signal transducer and activator of transcription 3 (STAT3) pathway in endothelial oxidative stress and mitochondria-dependent apoptosis, mTOR inhibitor rapamycin and STAT3 inhibitor S3I-201 were, respectively, used to inhibit mTOR/STAT3 signaling. Moreover, lentivirus vector-mediated mTORC1 (Raptor) and mTORC2 (Rictor) gene knockdown modifications were introduced to evaluate mTORC1 and mTORC1 pathways. Calcium measurement, reactive oxygen species (ROS) production, mitochondrial membrane potential and protein, cell proliferation, apoptosis, and endothelial junction protein were detected to evaluate HGF effects. Moreover, we used the ALI mouse model to observe the mitochondria pathological changes with an electron microscope in vivo.Results:Our study demonstrated that HGF protected the endothelium via the suppression of ROS production and intracellular calcium uptake, which lead to increased mitochondrial membrane potential (JC-1 and mitochondria tracker green detection) and specific proteins (complex I), raised anti-apoptosis Messenger Ribonucleic Acid level (B-cell lymphoma 2 and Bcl-xL), and increased endothelial junction proteins (VE-cadherin and occludin). Reversely, mTOR inhibitor rapamycin and STAT3 inhibitor S3I-201 could raise oxidative stress and mitochondria-dependent apoptosis even with HGF treatment in LPS-induced endothelial cells. Similarly, mTORC1 as well as mTORC2 have the same protective effects in mitochondria damage and apoptosis. In in vivo experiments of ALI mouse, HGF also increased mitochondria structural integrity via the mTOR/STAT3 pathway.Conclusion:In all, these reveal that mTOR/STAT3 signaling mediates the HGF suppression effects to oxidative level, mitochondria-dependent apoptosis, and endothelial junction protein in ARDS, contributing to the pulmonary endothelial survival and barrier integrity.

Uptake and timing of calcium in runner peanut (Arachis hypogaea L.)

Peanut production in the southeastern United States is often limited due to low Ca availability. Gypsum and lime are common Ca supplements for peanut, but the indeterminate nature of peanut and variable solubility of these products adds uncertainty to timing of Ca amendments. Two sets of field trials were performed in southern Alabama from 2012 to 2014 under both irrigated and non-irrigated conditions using two runner-type peanut cultivars (Georgia-06G and Georgia Greener) to determine Ca uptake patterns and timing of amendments. Calcium uptake was evaluated by pod development stage with four soil Ca treatments: 560 and 1120 kg ha −1 gypsum applied at early bloom, 1120 kg ha −1 lime at planting, and an untreated control. Developmental stages were determined by the hull scrape method. The timing of gypsum and lime was evaluated using metrics of peanut yield, grade, germination, and seed Ca. Treatments included a single application of gypsum at planting and early bloom, split applications of gypsum at planting/early bloom and early/mid-bloom, lime at planting, lime at planting plus gypsum at early bloom, and an untreated control. Results suggested that peanut absorbed Ca throughout the entire growing season and that seed Ca concentration could be used as an indicator of early-season seed quality. Split applications of gypsum at early/mid-bloom tended to have a superior performance than a single application at planting or early bloom and split applications at planting/early bloom. Supplemental gypsum at early bloom combined with lime at planting further increased Ca availability under non-irrigated conditions relative to the lime-only treatment. This study provided helpful information for Ca nutrient management for peanut.

Alcohol exacerbated biochemical and biophysical alterations in liver mitochondrial membrane of diabetic male wistar rats – A possible amelioration by green tea

Alcohol exacerbated biochemical and biophysical alterations in liver mitochondrial membrane of diabetic male wistar rats – A possible amelioration by green tea

Quantitative analysis of mitochondrial calcium uniporter (MCU) and essential MCU regulator (EMRE) in mitochondria from mouse tissues and HeLa cells

Mitochondrial calcium homeostasis plays critical roles in cell survival and aerobic metabolism in eukaryotes. The calcium uniporter is a highly selective calcium ion channel consisting of several subunits. Mitochondrial calcium uniporter (MCU) and essential MCU regulator (EMRE) are core subunits of the calcium uniporter required for calcium uptake activity in the mitochondria. Recent 3D structure analysis of the MCU‐EMRE complex reconstituted in nanodiscs revealed that the human MCU exists as a tetramer forming a channel pore, with EMRE bound to each MCU at a 1 : 1 ratio. However, the stoichiometry of MCU and EMRE in the mitochondria has not yet been investigated. We here quantitatively examined the protein levels of MCU and EMRE in the mitochondria from mouse tissues by using characterized antibodies and standard proteins. Unexpectedly, the number of EMRE molecules was lower than that of MCU; moreover, the ratios between MCU and EMRE were significantly different among tissues. Statistical calculations based on our findings suggest that a MCU tetramer binding to 4 EMREs may exist, but at low levels in the mitochondrial inner membrane. In brain mitochondria, the majority of MCU tetramers bind to 2 EMREs; in mitochondria in liver, kidney, and heart, MCU tetramers bind to 1 EMRE; and in kidney and heart, almost half of MCU tetramers bound to no EMRE. We propose here a novel stoichiometric model of the MCU‐EMRE complex in mitochondria.

MICU1-dependent mitochondrial calcium uptake regulates lung alveolar type 2 cell plasticity and lung regeneration.

Lung alveolar type 2 (AT2) cells are progenitors for alveolar type 1 (AT1) cells. Although many factors regulate AT2 cell plasticity, the role of mitochondrial calcium (mCa2+) uptake in controlling AT2 cells remains unclear. We previously identified that the miR-302 family supports lung epithelial progenitor cell proliferation and less differentiated phenotypes during development. Here, we report that a sustained elevation of miR-302 in adult AT2 cells decreases AT2-to-AT1 cell differentiation during the Streptococcus pneumoniae–induced lung injury repair. We identified that miR-302 targets and represses the expression of mitochondrial Ca2+ uptake 1 (MICU1), which regulates mCa2+ uptake through the mCa2+ uniporter channel by acting as a gatekeeper at low cytosolic Ca2+ levels. Our results reveal a marked increase in MICU1 protein expression and decreased mCa2+ uptake during AT2-to-AT1 cell differentiation in the adult lung. Deletion of Micu1 in AT2 cells reduces AT2-to-AT1 cell differentiation during steady-state tissue maintenance and alveolar epithelial regeneration after bacterial pneumonia. These studies indicate that mCa2+ uptake is extensively modulated during AT2-to-AT1 cell differentiation and that MICU1-dependent mCa2+ uniporter channel gating is a prominent mechanism modulating AT2-to-AT1 cell differentiation.

Regenerating islet-derived protein 3 gamma (Reg3g) ameliorates tacrolimus-induced pancreatic β-cell dysfunction in mice by restoring mitochondrial function.

Tacrolimus a first-line medication used after transplantation can induce β-cell dysfunction, causing new-onset diabetes mellitus (NODM). Regenerating islet-derived protein 3 gamma (Reg3g), a member of the pancreatic regenerative gene family, has been reported to improve type 1 diabetes by promoting β-cell regeneration. We aim to investigate the role of Reg3g in reversing tacrolimus-induced β-cell dysfunction and NODM in mice. Circulating REG3A (the human homologue of mouse Reg3g) in heart transplantation patients treated with tacrolimus was detected. The glucose-stimulated insulin secretion and mitochondrial functions, including mitochondria membrane potential (MMP), mitochondria calcium, ATP production, oxygen consumption rate and mitochondrial morphology were investigated in β-cells. Additionally, effects of Reg3g on tacrolimus-induced NODM in mice were analysed. Circulating REG3A level in heart transplantation patients with NODM significantly decreased compared with those without diabetes. Tacrolimus down-regulated Reg3g via inhibiting STAT3-mediated transcription activation. Moreover, Reg3g restored glucose-stimulated insulin secretion suppressed by tacrolimus in β-cells by improving mitochondrial functions, including increased MMP, mitochondria calcium uptake, ATP production, oxygen consumption rate and contributing to an intact mitochondrial morphology. Mechanistically, Reg3g increased accumulation of pSTAT3(Ser727) in mitochondria by activating ERK1/2-STAT3 signalling pathway, leading to restoration of tacrolimus-induced mitochondrial impairment. Reg3g overexpression also effectively mitigated tacrolimus-induced NODM in mice. Reg3g can significantly ameliorate tacrolimus-induced β-cell dysfunction by restoring mitochondrial function in a pSTAT3(Ser727)-dependent manner. Our observations identify a novel Reg3g-mediated mechanism that is involved in tacrolimus-induced NODM and establish the novel role of Reg3g in reversing tacrolimus-induced β-cell dysfunction.

Articles of Significant Interest in This Issue

(e00551-21). Infection and Immunity. Volume 90 Issue: 2. Mitochondrial calcium uptake 1 (MICU1) regulates mitochondrial calcium uptake and prevents mitochondrial calcium overload. MICU1-deficient neutrophils accumulate metals within the mitochondria, have increased mitochondrial superoxide production, and enhanced propensity to undergo NETosis. Increased NETosis upon loss of MICU1 correlates with an enhanced cooperative killing of S. aureus by neutrophils and macrophages and protection against S. aureus infection of the heart.

Notch1 Modulation of Cellular Calcium Regulates Mitochondrial Metabolism and Anti-Apoptotic Activity in T-Regulatory Cells.

As the major hub of metabolic activity and an organelle sequestering pro-apoptogenic intermediates, mitochondria lie at the crossroads of cellular decisions of death and survival. Intracellular calcium is a key regulator of these outcomes with rapid, uncontrolled uptake into mitochondria, activating pro-apoptotic cascades that trigger cell death. Here, we show that calcium uptake and mitochondrial metabolism in murine T-regulatory cells (Tregs) is tuned by Notch1 activity. Based on analysis of Tregs and the HEK cell line, we present evidence that modulation of cellular calcium dynamics underpins Notch1 regulation of mitochondrial homeostasis and consequently anti-apoptotic activity. Targeted siRNA-mediated ablations reveal dependency on molecules controlling calcium release from the endoplasmic reticulum (ER) and the chaperone, glucose-regulated protein 75 (Grp75), the associated protein Voltage Dependent Anion Channel (VDAC)1 and the Mitochondrial Calcium Uniporter (MCU), which together facilitate ER calcium transfer and uptake into the mitochondria. Endogenous Notch1 is detected in immune-complexes with Grp75 and VDAC1. Deficits in mitochondrial oxidative and survival in Notch1 deficient Tregs, were corrected by the expression of recombinant Notch1 intracellular domain, and in part by recombinant Grp75. Thus, the modulation of calcium dynamics and consequently mitochondrial metabolism underlies Treg survival in conditions of nutrient stress. This work positions a key role for Notch1 activity in these outcomes.

Lysophosphatidic Acid Receptor 3 Promotes Mitochondrial Homeostasis against Oxidative Stress: Potential Therapeutic Approaches for Hutchinson-Gilford Progeria Syndrome.

Lysophosphatidic acid (LPA) is a growth factor-like lipid mediator that regulates various physiological functions via activation of multiple LPA G protein-coupled receptors. We previously reported that LPA suppresses oxidative stress in premature aging Hutchinson-Gilford progeria syndrome (HGPS) patient fibroblasts via its type 3 receptor (LPA3). Mitochondria have been suggested to be the primary origin of oxidative stress via the overproduction of reactive oxygen species (ROS). Mitochondria are responsible for producing ATP through oxidative phosphorylation (OXPHOS) and have a calcium buffering capacity for the cell. Defects in mitochondria will lead to declined antioxidant capacity and cell apoptosis. Therefore, we aim to demonstrate the regulatory role of LPA3 in mitochondrial homeostasis. siRNA-mediated depletion of LPA3 leads to the depolarization of mitochondrial potential (ΔΨm) and cellular ROS accumulation. In addition, the depletion of LPA3 enhances cisplatin-induced cytochrome C releasing. This indicates that LPA3 is essential to suppress the mitochondrial apoptosis pathway. LPA3 is also shown to improve mitochondrial ADP-ATP exchange by enhancing the protein level of ANT2. On the other hand, LPA3 regulates calcium uptake from the ER to mitochondria via the IP3R1-VDAC1 channel. Moreover, activation of LPA3 by selective agonist OMPT rescues mitochondrial homeostasis of H2O2-induced oxidative stress cells and HGPS patient fibroblasts by improving mitochondrial ΔΨm and OXPHOS. In summary, our findings imply that LPA3 acts as the gatekeeper for mitochondrial healthiness to maintain cell youth. Furthermore, LPA3 can be a promising therapeutic target to prevent mitochondrial oxidative stress in aging and HGPS.

Ruthenium 360 and mitoxantrone inhibit mitochondrial calcium uniporter channel to prevent liver steatosis induced by high-fat diet.

Non-alcoholic fatty liver disease (NAFLD) affects over 25% of the general population and lacks an effective treatment. Recent evidence implicates disrupted mitochondrial calcium homeostasis in the pathogenesis of hepatic steatosis. In this study, mitochondrial calcium uniporter (MCU) was inhibited through classical genetic approaches, viral vectors or small molecule inhibitors in vivo to study its role in hepatic steatosis induced by high-fat diet (HFD). In vitro, MCU was overexpressed or inhibited to change mitochondrial calcium homeostasis, endoplasmic reticulum-mitochondrial linker was adopted to increase mitochondria-associated membranes (MAMs) and MICU1-EF hand mutant was used to decrease the sensitivity of mitochondrial calcium uptake 1 (MICU1) to calcium and block MCU channel. Here, we found that inhibition of liver MCU by AAV virus and classical genetic approaches can prevent HFD-induced liver steatosis. MCU regulates mitochondrial calcium homeostasis and affects lipid accumulation in liver cells. In addition, a HFD in mice enlarged the MAM. The high-calcium environment produced by MAM invalidated the function of MICU1 and led to persistent open of MCU channels. Therefore, it caused mitochondrial calcium overload and liver fat deposition. Inhibition of MAM and MCU alleviated HFD-induced hepatic steatosis. MCU inhibitors (Ru360 and mitoxantrone) can block MCU channels and reduce mitochondrial calcium levels. Intraperitoneal injection of MCU inhibitors (0.01-μM·kg-1 bodyweight) can alleviate HFD-induced hepatic steatosis. These findings provide molecular insights into the way HFD disrupts mitochondrial calcium homeostasis and identify MCU as a promising drug target for the treatment of hepatic steatosis.

Contraction and electrophysiological abnormalities in myofilament mutation-positive and mutation-negative human HCM myocardium

Myofilament mutation-positive and mutation-negative hypertrophic cardiomyopathy (HCM) patients show different prognosis and arrhythmic burden that are likely related to the different pathogenesis. For instance, post-translational activation of CaMKII pathway is a specific biomarker of myofilament mutation-positive HCM while depressed sarcoplasmic reticulum calcium uptake is present in both groups. However, the functional consequences of a mutation-driven pathogenesis is still not completely understood.