The cell membrane repair protein MG53 modulates transcription factor NF-κB signaling to control kidney fibrosis.

Kidney fibrosis is associated with the progression of acute kidney injury to chronic kidney disease. MG53, a cell membrane repair protein, has been shown to protect against injury to kidney epithelial cells and acute kidney injury. Here, we evaluated the role of MG53 in modulation of kidney fibrosis in aging mice and in mice with unilateral ureteral obstruction (UUO) a known model of progressive kidney fibrosis. Mice with ablation of MG53 developed more interstitial fibrosis with age than MG53-intact mice of the same age. Similarly, in the absence of MG53, kidney fibrosis was exaggerated compared to mice with intact MG53 in the obstructed kidney compared to the contralateral unobstructed kidney or the kidneys of sham operated mice. The ureteral obstructed kidneys from MG53 deficient mice also showed significantly more inflammation than ureteral obstructed kidneys from MG53 intact mice. In vitro experiments demonstrated that MG53 could enter the nuclei of proximal tubular epithelial cells and directly interact with the p65 component of transcription factor NF-κB, providing a possible explanation of enhanced inflammation in the absence of MG53. To test this, enhanced MG53 expression through engineered cells or direct recombinant protein delivery was given to mice subject to UUO. This reduced NF-κB activation and inflammation and attenuated kidney fibrosis. Thus, MG53 may have a therapeutic role in treating chronic kidney inflammation and thereby provide protection against fibrosis that leads to the chronic kidney disease phenotype.

TRIC-A Channel Maintains Store Calcium Handling by Interacting With Type 2 Ryanodine Receptor in Cardiac Muscle.

RATIONALE: Trimeric intracellular cation (TRIC)-A and B are distributed to endoplasmic reticulum/sarcoplasmic reticulum intracellular Ca2+ stores. The crystal structure of TRIC has been determined, confirming the homotrimeric structure of a potassium channel. While the pore architectures of TRIC-A and TRIC-B are conserved, the carboxyl-terminal tail (CTT) domains of TRIC-A and TRIC-B are different from each other. Aside from its recognized role as a counterion channel that participates in excitation-contraction coupling of striated muscles, the physiological function of TRIC-A in heart physiology and disease has remained largely unexplored. OBJECTIVE: In cardiomyocytes, spontaneous Ca2+ waves, triggered by store overload-induced Ca2+ release mediated by the RyR2 (type 2 ryanodine receptor), develop extrasystolic contractions often associated with arrhythmic events. Here, we test the hypothesis that TRIC-A is a physiological component of RyR2-mediated Ca2+ release machinery that directly modulates store overload-induced Ca2+ release activity via CTT. METHODS AND RESULTS: We show that cardiomyocytes derived from the TRIC-A-/- (TRIC-A knockout) mice display dysregulated Ca2+ movement across sarcoplasmic reticulum. Biochemical studies demonstrate a direct interaction between CTT-A and RyR2. Modeling and docking studies reveal potential sites on RyR2 that show differential interactions with CTT-A and CTT-B. In HEK293 (human embryonic kidney) cells with stable expression of RyR2, transient expression of TRIC-A, but not TRIC-B, leads to apparent suppression of spontaneous Ca2+ oscillations. Ca2+ measurements using the cytosolic indicator Fura-2 and the endoplasmic reticulum luminal store indicator D1ER suggest that TRIC-A enhances Ca2+ leak across the endoplasmic reticulum by directly targeting RyR2 to modulate store overload-induced Ca2+ release. Moreover, synthetic CTT-A peptide facilitates RyR2 activity in lipid bilayer reconstitution system, enhances Ca2+ sparks in permeabilized TRIC-A-/- cardiomyocytes, and induces intracellular Ca2+ release after microinjection into isolated cardiomyocytes, whereas such effects were not observed with the CTT-B peptide. In response to isoproterenol stimulation, the TRIC-A-/- mice display irregular ECG and develop more fibrosis than the WT (wild type) littermates. CONCLUSIONS: In addition to the ion-conducting function, TRIC-A functions as an accessory protein of RyR2 to modulate sarcoplasmic reticulum Ca2+ handling in cardiac muscle.

TRIC-A regulates intracellular Ca2+ homeostasis in cardiomyocytes.

Trimeric intracellular cation (TRIC) channels have been identified as monovalent cation channels that are located in the ER/SR membrane. Two isoforms discovered in mammals are TRIC-A (TMEM38a) and TRIC-B (TMEM38b). TRIC-B ubiquitously expresses in all tissues, and TRIC-B-/- mice is lethal at the neonatal stage. TRIC-A mainly expresses in excitable cells. TRIC-A-/- mice survive normally but show abnormal SR Ca2+ handling in both skeletal and cardiac muscle cells. Importantly, TRIC-A mutations have been identified in human patients with stress-induced arrhythmia. In the past decade, important discoveries have been made to understand the structure and function of TRIC channels, especially its role in regulating intracellular Ca2+ homeostasis. In this review article, we focus on the potential roles of TRIC-A in regulating cardiac function, particularly its effects on intracellular Ca2+ signaling of cardiomyocytes and discuss the current knowledge gaps.

MG53 suppresses tumor progression and stress granule formation by modulating G3BP2 activity in non-small cell lung cancer.

BACKGROUND: Cancer cells develop resistance to chemotherapeutic intervention by excessive formation of stress granules (SGs), which are modulated by an oncogenic protein G3BP2. Selective control of G3BP2/SG signaling is a potential means to treat non-small cell lung cancer (NSCLC). METHODS: Co-immunoprecipitation was conducted to identify the interaction of MG53 and G3BP2. Immunohistochemistry and live cell imaging were performed to visualize the subcellular expression or co-localization. We used shRNA to knock-down the expression MG53 or G3BP2 to test the cell migration and colony formation. The expression level of MG53 and G3BP2 in human NSCLC tissues was tested by western blot analysis. The ATO-induced oxidative stress model was used to examine the effect of rhMG53 on SG formation. Moue NSCLC allograft experiments were performed on wild type and transgenic mice with either knockout of MG53, or overexpression of MG53. Human NSCLC xenograft model in mice was used to evaluate the effect of MG53 overexpression on tumorigenesis. RESULTS: We show that MG53, a member of the TRIM protein family (TRIM72), modulates G3BP2 activity to control lung cancer progression. Loss of MG53 results in the progressive development of lung cancer in mg53-/- mice. Transgenic mice with sustained elevation of MG53 in the bloodstream demonstrate reduced tumor growth following allograft transplantation of mouse NSCLC cells. Biochemical assay reveals physical interaction between G3BP2 and MG53 through the TRIM domain of MG53. Knockdown of MG53 enhances proliferation and migration of NSCLC cells, whereas reduced tumorigenicity is seen in NSCLC cells with knockdown of G3BP2 expression. The recombinant human MG53 (rhMG53) protein can enter the NSCLC cells to induce nuclear translation of G3BP2 and block arsenic trioxide-induced SG formation. The anti-proliferative effect of rhMG53 on NSCLC cells was abolished with knockout of G3BP2. rhMG53 can enhance sensitivity of NSCLC cells to undergo cell death upon treatment with cisplatin. Tailored induction of MG53 expression in NSCLC cells suppresses lung cancer growth via reduced SG formation in a xenograft model. CONCLUSION: Overall, these findings support the notion that MG53 functions as a tumor suppressor by targeting G3BP2/SG activity in NSCLCs.

MG53 protects against contrast-induced acute kidney injury by reducing cell membrane damage and apoptosis.

Mitsugumin 53 (MG53) is a tripartite motif family protein that has been reported to attenuate injury via membrane repair in different organs. Contrast-induced acute kidney injury (CI-AKI) is a common complication caused by the administration of iodinated contrast media (CM). While the cytotoxicity induced by CM leading to tubular cell death may be initiated by cell membrane damage, we wondered whether MG53 alleviates CI-AKI. This study was designed to investigate the effect of MG53 on CI-AKI and the underlying mechanism. A rat model of CI-AKI was established, and CI-AKI induced the translocation of MG53 from serum to injury sites on the renal proximal tubular (RPT) epithelia, as illustrated by immunoblot analysis and immunohistochemical staining. Moreover, pretreatment of rats with recombinant human MG53 protein (rhMG53, 2 mg/mL) alleviated iopromide-induced injury in the kidney, which was determined by measuring serum creatinine, blood urea nitrogen and renal histological changes. In vitro studies demonstrated that exposure of RPT cells to iopromide (20, 40, and 80 mg/mL) caused cell membrane injury and cell death, which were attenuated by rhMG53 (10 and 50 µg/mL). Mechanistically, MG53 translocated to the injury site on RPT cells and bound to phosphatidylserine to protect RPT cells from iopromide-induced injury. In conclusion, MG53 protects against CI-AKI through cell membrane repair and reducing cell apoptosis; therefore, rhMG53 might be a potential effective means to treat or prevent CI-AKI.

Sustained Release of a Peptide-Based Matrix Metalloproteinase-2 Inhibitor to Attenuate Adverse Cardiac Remodeling and Improve Cardiac Function Following Myocardial Infarction.

Following myocardial infarction (MI), degradation of extracellular matrix (ECM) by upregulated matrix metalloproteinases (MMPs) especially MMP-2 decreases tissue mechanical properties, leading to cardiac function deterioration. Attenuation of cardiac ECM degradation at the early stage of MI has the potential to preserve tissue mechanical properties, resulting in cardiac function increase. Yet the strategy for efficiently preventing cardiac ECM degradation remains to be established. Current preclinical approaches have shown limited efficacy because of low drug dosage allocated to the heart tissue, dose-limiting side effects, and cardiac fibrosis. To address these limitations, we have developed a MMP-2 inhibitor delivery system that can be specifically delivered into infarcted hearts at early stage of MI to efficiently prevent MMP-2-mediated ECM degradation. The system was based on an injectable, degradable, fast gelation, and thermosensitive hydrogel, and a MMP-2 specific inhibitor, peptide CTTHWGFTLC (CTT). The use of fast gelation hydrogel allowed to completely retain CTT in the heart tissue. The system was able to release low molecular weight CTT over 4 weeks possibly due to the strong hydrogen bonding between the hydrogel and CTT. The release kinetics was modulated by amount of CTT loaded into the hydrogel, and using chondroitin sulfate and heparin that can interact with CTT and the hydrogel. Both glycosaminoglycans augmented CTT release, while heparin more greatly accelerated the release. After it was injected into the infarcted hearts for 4 weeks, the released CTT efficiently prevented cardiac ECM degradation as it not only increased tissue thickness but also preserved collagen composition similar to that in the normal heart tissue. In addition, the delivery system significantly improved cardiac function. Importantly, the delivery system did not induce cardiac fibrosis. These results demonstrate that the developed MMP-2 inhibitor delivery system has potential to efficiently reduce adverse myocardial remodeling and improve cardiac function.

Mitochondria Damage and Kidney Disease.

The kidney is a vital organ that demands an extraordinary amount of energy to actively maintain the body's metabolism, plasma hemodynamics, electrolytes and water homeostasis, nutrients reabsorption, and hormone secretion. Kidney is only second to the heart in mitochondrial count and oxygen consumption. As such, the health and status of the energy power house, the mitochondria, is pivotal to the health and proper function of the kidney. Mitochondria are heterogeneous and highly dynamic organelles and their functions are subject to complex regulations through modulation of its biogenesis, bioenergetics, dynamics and clearance within cell. Kidney diseases, either acute kidney injury (AKI) or chronic kidney disease (CKD), are important clinical issues and global public health concerns with high mortality rate and socioeconomic burden due to lack of effective therapeutic strategies to cure or retard the progression of the diseases. Mitochondria-targeted therapeutics has become a major focus for modern research with the belief that maintaining mitochondria homeostasis can prevent kidney pathogenesis and disease progression. A better understanding of the cellular and molecular events that govern mitochondria functions in health and disease will potentially lead to improved therapeutics development.

Production of oridonin-rich extracts from Rabdosia rubescens using hyphenated ultrasound-assisted supercritical carbon dioxide extraction.

BACKGROUND: Among active components in Rabdosia rubescens, oridonin has been considered a key component and the most valuable compound because it has a wide range of activities beneficial to human health. To produce a high-quality oridonin extract, an alternative hyphenated procedure involving an ultrasound-assisted and supercritical carbon dioxide (HSC-CO2 ) extraction method to extract oridonin from R. rubescens was developed in this study. Fictitious solubilities of oridonin in supercritical CO2 (SC-CO2 ) with ultrasound assistance were measured by using the dynamic method at temperatures ranging from 305.15 K to 342.15 K over a pressure range of 11.5 to 33.5 MPa. RESULTS: Fictitious solubilities of oridonin at different temperatures and pressures were over the range of 2.13 × 10-6 to 10.09 × 10-6 (mole fraction) and correlated well with the density-based models, including the Bartle model, the Chrastil model, the Kumar and Johnston model and the Mendez-Santiago and Teja model, with overall average absolute relative deviations (AARDs) of 6.29%, 4.39%, 3.12% and 5.07%, respectively. CONCLUSION: Oridonin exhibits retrograde solubility behaviour in the supercritical state. Fictitious solubility data were further determined and obtained a good fit with four semi-empirical models. Simultaneously, the values of the total heat of solution, vaporisation and solvation of oridonin were estimated. © 2016 Society of Chemical Industry.

Lysosomal two-pore channel subtype 2 (TPC2) regulates skeletal muscle autophagic signaling.

Postnatal skeletal muscle mass is regulated by the balance between anabolic protein synthesis and catabolic protein degradation, and muscle atrophy occurs when protein homeostasis is disrupted. Autophagy has emerged as critical in clearing dysfunctional organelles and thus in regulating protein turnover. Here we show that endolysosomal two-pore channel subtype 2 (TPC2) contributes to autophagy signaling and protein homeostasis in skeletal muscle. Muscles derived from Tpcn2(-/-) mice exhibit an atrophic phenotype with exacerbated autophagy under starvation. Compared with wild types, animals lacking TPC2 demonstrated an enhanced autophagy flux characterized by increased accumulation of autophagosomes upon combined stress induction by starvation and colchicine treatment. In addition, deletion of TPC2 in muscle caused aberrant lysosomal pH homeostasis and reduced lysosomal protease activity. Association between mammalian target of rapamycin and TPC2 was detected in skeletal muscle, allowing for appropriate adjustments to cellular metabolic states and subsequent execution of autophagy. TPC2 therefore impacts mammalian target of rapamycin reactivation during the process of autophagy and contributes to maintenance of muscle homeostasis.

Modulation of wound healing and scar formation by MG53 protein-mediated cell membrane repair.

Cell membrane repair is an important aspect of physiology, and disruption of this process can result in pathophysiology in a number of different tissues, including wound healing, chronic ulcer and scarring. We have previously identified a novel tripartite motif family protein, MG53, as an essential component of the cell membrane repair machinery. Here we report the functional role of MG53 in the modulation of wound healing and scarring. Although MG53 is absent from keratinocytes and fibroblasts, remarkable defects in skin architecture and collagen overproduction are observed in mg53(-/-) mice, and these animals display delayed wound healing and abnormal scarring. Recombinant human MG53 (rhMG53) protein, encapsulated in a hydrogel formulation, facilitates wound healing and prevents scarring in rodent models of dermal injuries. An in vitro study shows that rhMG53 protects against acute injury to keratinocytes and facilitates the migration of fibroblasts in response to scratch wounding. During fibrotic remodeling, rhMG53 interferes with TGF-ß-dependent activation of myofibroblast differentiation. The resulting down-regulation of α smooth muscle actin and extracellular matrix proteins contributes to reduced scarring. Overall, these studies establish a trifunctional role for MG53 as a facilitator of rapid injury repair, a mediator of cell migration, and a modulator of myofibroblast differentiation during wound healing. Targeting the functional interaction between MG53 and TGF-ß signaling may present a potentially effective means for promoting scarless wound healing.

Autophagy, Innate Immunity and Tissue Repair in Acute Kidney Injury.

Kidney is a vital organ with high energy demands to actively maintain plasma hemodynamics, electrolytes and water homeostasis. Among the nephron segments, the renal tubular epithelium is endowed with high mitochondria density for their function in active transport. Acute kidney injury (AKI) is an important clinical syndrome and a global public health issue with high mortality rate and socioeconomic burden due to lack of effective therapy. AKI results in acute cell death and necrosis of renal tubule epithelial cells accompanied with leakage of tubular fluid and inflammation. The inflammatory immune response triggered by the tubular cell death, mitochondrial damage, associative oxidative stress, and the release of many tissue damage factors have been identified as key elements driving the pathophysiology of AKI. Autophagy, the cellular mechanism that removes damaged organelles via lysosome-mediated degradation, had been proposed to be renoprotective. An in-depth understanding of the intricate interplay between autophagy and innate immune response, and their roles in AKI pathology could lead to novel therapies in AKI. This review addresses the current pathophysiology of AKI in aspects of mitochondrial dysfunction, innate immunity, and molecular mechanisms of autophagy. Recent advances in renal tissue regeneration and potential therapeutic interventions are also discussed.

Type 1 inositol (1,4,5)-trisphosphate receptor activates ryanodine receptor 1 to mediate calcium spark signaling in adult mammalian skeletal muscle.

Functional coupling between inositol (1,4,5)-trisphosphate receptor (IP(3)R) and ryanodine receptor (RyR) represents a critical component of intracellular Ca(2+) signaling in many excitable cells; however, the role of this mechanism in skeletal muscle remains elusive. In skeletal muscle, RyR-mediated Ca(2+) sparks are suppressed in resting conditions, whereas application of transient osmotic stress can trigger activation of Ca(2+) sparks that are restricted to the periphery of the fiber. Here we show that onset of these spatially confined Ca(2+) sparks involves interaction between activation of IP(3)R and RyR near the sarcolemmal membrane. Pharmacological prevention of IP(3) production or inhibition of IP(3)R channel activity abolishes stress-induced Ca(2+) sparks in skeletal muscle. Although genetic ablation of the type 2 IP(3)R does not appear to affect Ca(2+) sparks in skeletal muscle, specific silencing of the type 1 IP(3)R leads to ablation of stress-induced Ca(2+) sparks. Our data indicate that membrane-delimited signaling involving cross-talk between IP(3)R1 and RyR1 contributes to Ca(2+) spark activation in skeletal muscle.

Superresolution microscope image reconstruction by spatiotemporal object decomposition and association: application in resolving t-tubule structure in skeletal muscle.

One key factor that limits resolution of single-molecule superresolution microscopy relates to the localization accuracy of the activated emitters, which is usually deteriorated by two factors. One originates from the background noise due to out-of-focus signals, sample auto-fluorescence, and camera acquisition noise; and the other is due to the low photon count of emitters at a single frame. With fast acquisition rate, the activated emitters can last multiple frames before they transiently switch off or permanently bleach. Effectively incorporating the temporal information of these emitters is critical to improve the spatial resolution. However, majority of the existing reconstruction algorithms locate the emitters frame by frame, discarding or underusing the temporal information. Here we present a new image reconstruction algorithm based on tracklets, short trajectories of the same objects. We improve the localization accuracy by associating the same emitters from multiple frames to form tracklets and by aggregating signals to enhance the signal to noise ratio. We also introduce a weighted mean-shift algorithm (WMS) to automatically detect the number of modes (emitters) in overlapping regions of tracklets so that not only well-separated single emitters but also individual emitters within multi-emitter groups can be identified and tracked. In combination with a maximum likelihood estimator method (MLE), we are able to resolve low to medium density of overlapping emitters with improved localization accuracy. We evaluate the performance of our method with both synthetic and experimental data, and show that the tracklet-based reconstruction is superior in localization accuracy, particularly for weak signals embedded in a strong background. Using this method, for the first time, we resolve the transverse tubule structure of the mammalian skeletal muscle.

TRIC channels are essential for Ca2+ handling in intracellular stores.

Cell signalling requires efficient Ca2+ mobilization from intracellular stores through Ca2+ release channels, as well as predicted counter-movement of ions across the sarcoplasmic/endoplasmic reticulum membrane to balance the transient negative potential generated by Ca2+ release. Ca2+ release channels were cloned more than 15 years ago, whereas the molecular identity of putative counter-ion channels remains unknown. Here we report two TRIC (trimeric intracellular cation) channel subtypes that are differentially expressed on intracellular stores in animal cell types. TRIC subtypes contain three proposed transmembrane segments, and form homo-trimers with a bullet-like structure. Electrophysiological measurements with purified TRIC preparations identify a monovalent cation-selective channel. In TRIC-knockout mice suffering embryonic cardiac failure, mutant cardiac myocytes show severe dysfunction in intracellular Ca2+ handling. The TRIC-deficient skeletal muscle sarcoplasmic reticulum shows reduced K+ permeability, as well as altered Ca2+ 'spark' signalling and voltage-induced Ca2+ release. Therefore, TRIC channels are likely to act as counter-ion channels that function in synchronization with Ca2+ release from intracellular stores.

Editorial: Highlights in Autophagy-From Basic Mechanisms to Human Disorder Treatments.

Autophagy is an evolutionarily conserved catabolic process and represents a field of research that is constantly growing [...].

MG53 inhibits cellular proliferation and tumor progression in colorectal carcinoma.

Cancer is the second leading cause of mortality after cardiovascular diseases in the United States. Chemotherapy is widely used to treat cancers. Since the development of drug resistance is a major contributor towards the failure of chemotherapeutic regimens, efforts have been made to develop novel inhibitors that can combat drug resistance and sensitize cancer cells to chemotherapy. Here we investigated the anti-cancer effects of MG53, a TRIM-family protein known for its membrane repair functions. We found that rhMG53 reduced cellular proliferation of both parental and ABCB1 overexpressing colorectal carcinoma cells. Exogenous rhMG53 protein entered SW620 and SW620/AD300 cells without altering the expression of ABCB1 protein. In a mouse SW620/AD300 xenograft model, the combination of rhMG53 and doxorubicin treatment significantly inhibited tumor growth without any apparent weight loss or hematological toxicity in the animals. Our data show that MG53 has anti-proliferative function on colorectal carcinoma, regardless of their nature to drug-resistance. This is important as it supports the broader value for rhMG53 as a potential adjuvant therapeutic to treat cancers even when drug-resistance develops.

MG53 preserves mitochondrial integrity of cardiomyocytes during ischemia reperfusion-induced oxidative stress.

Ischemic injury to the heart induces mitochondrial dysfunction due to increasing oxidative stress. MG53, also known as TRIM72, is highly expressed in striated muscle, is secreted as a myokine after exercise, and is essential for repairing damaged plasma membrane of many tissues by interacting with the membrane lipid phosphatidylserine (PS). We hypothesized MG53 could preserve mitochondrial integrity after an ischemic event by binding to the mitochondrial-specific lipid, cardiolipin (CL), for mitochondria protection to prevent mitophagy. Fluorescent imaging and Western blotting experiments showed recombinant human MG53 (rhMG53) translocated to the mitochondria after ischemic injury in vivo and in vitro. Fluorescent imaging indicated rhMG53 treatment reduced superoxide generation in ex vivo and in vitro models. Lipid-binding assay indicated MG53 binds to CL. Transfecting cardiomyocytes with the mitochondria-targeted mt-mKeima showed inhibition of mitophagy after MG53 treatment. Overall, we show that rhMG53 treatment may preserve cardiac function by preserving mitochondria in cardiomyocytes. These findings suggest MG53's interactions with mitochondria could be an attractive avenue for developing MG53 as a targeted protein therapy for cardioprotection.

Wound Matrix Stiffness Imposes on Macrophage Activation.

The immune system depends on two major paths-the innate and the adaptive immunity. Macrophage, with its unique features as the first line of immune defense to engulf and digest invaders, serves as the key effector cells integrating those two paths. The dynamic plasticity of macrophage activation during wound repair, inflammation resolution, and tissue remodeling are emerging biomedical and bioengineering hot topics in immune function studies such as the various secretions of cytokines and chemokines and the signaling pathways with ligands and their cognate receptors. Better knowledge on how physical/mechanical and multicellular microenvironment on the modulation of macrophage functions will create innovative therapies to boost host defense mechanism and assist wound healing. In this, we describe an easy method to measure functions (gene expressions) of human and mouse macrophages in response to mechanical microenvironment changes by embedding isolated macrophages in polymerized hyaluronan gel with different wound matrix stiffness.

Dyslipidemia in Kidney Disorders: Perspectives on Mitochondria Homeostasis and Therapeutic Opportunities.

To excrete body nitrogen waste and regulate electrolyte and fluid balance, the kidney has developed into an energy factory with only second to the heart in mitochondrial content in the body to meet the high-energy demand and regulate homeostasis. Energy supply from the renal mitochondria majorly depends on lipid metabolism, with programed enzyme systems in fatty acid ß-oxidation and Krebs cycle. Renal mitochondria integrate several metabolic pathways, including AMPK/PGC-1α, PPARs, and CD36 signaling to maintain energy homeostasis for dynamic and static requirements. The pathobiology of several kidney disorders, including diabetic nephropathy, acute and chronic kidney injuries, has been primarily linked to impaired mitochondrial bioenergetics. Such homeostatic disruption in turn stimulates a pathological adaptation, with mitochondrial enzyme system reprograming possibly leading to dyslipidemia. However, this alteration, while rescuing oncotic pressure deficit secondary to albuminuria and dissipating edematous disorder, also imposes an ominous lipotoxic consequence. Reprograming of lipid metabolism in kidney injury is essential to preserve the integrity of kidney mitochondria, thereby preventing massive collateral damage including excessive autophagy and chronic inflammation. Here, we review dyslipidemia in kidney disorders and the most recent advances on targeting mitochondrial energy metabolism as a therapeutic strategy to restrict renal lipotoxicity, achieve salutary anti-edematous effects, and restore mitochondrial homeostasis.

MG53 suppresses interferon-ß and inflammation via regulation of ryanodine receptor-mediated intracellular calcium signaling.

TRIM family proteins play integral roles in the innate immune response to virus infection. MG53 (TRIM72) is essential for cell membrane repair and is believed to be a muscle-specific TRIM protein. Here we show human macrophages express MG53, and MG53 protein expression is reduced following virus infection. Knockdown of MG53 in macrophages leads to increases in type I interferon (IFN) upon infection. MG53 knockout mice infected with influenza virus show comparable influenza virus titres to wild type mice, but display increased morbidity accompanied by more accumulation of CD45+ cells and elevation of IFNß in the lung. We find that MG53 knockdown results in activation of NFκB signalling, which is linked to an increase in intracellular calcium oscillation mediated by ryanodine receptor (RyR). MG53 inhibits IFNß induction in an RyR-dependent manner. This study establishes MG53 as a new target for control of virus-induced morbidity and tissue injury.