S100A16 promotes acute kidney injury by activating HRD1-induced ubiquitination and degradation of GSK3β and CK1α

The roles of the ubiquitin-proteasome system in renal disease

The ubiquitin-proteasome system (UPS) is a major pathway of specific intracellular protein degradation through proteasome degradation of ubiquitin-labeled substrates. Numerous biological processes, including the cell cycle, transcription, translation, apoptosis, receptor activity, and intracellular signaling, are regulated by UPS. Alterations of the UPS, which render them more or less susceptible to degradation, are responsible for disorders of renal diseases. This review aims to summarize the mechanism of UPS in renal diseases. Besides, this review explores the relationship among UPS, autophagy, and deubiquitination in the development of renal disease. The specific molecular linkages among these systems and pathogenesis, on the other hand, are unknown and controversial. In addition, we briefly describe some anti-renal disease agents targeting UPS components. This review emphasizes UPS as a promising therapeutic modality for the treatment of kidney disease. Our work, though still basic and limited, could provide options to future potential therapeutic targets for renal diseases with a UPS underlying basis.

Renal tubular S100A7a impairs fatty acid oxidation and exacerbates renal fibrosis via both intracellular and extracellular pathway

A couple of S100 family proteins (S100s) have been reported to exert pro-inflammatory functions in the progression of renal fibrosis. Unlike some S100s which are expressed by both epithelial and stromal inflammatory cells, S100A7 is restricted expressed in epithelium. Persistent S100A7 expression occurs in some invasive carcinomas and is associated with poor prognostic factors. Whereas, whether it is implicated in renal tubular epithelial cell injury and kidney disease remains unexplored. In this study, we demonstrate that S100A7 is highly upregulated in tubular cells of both mouse renal fibrotic lesions and kidney biopsies from patients with chronic kidney disease (CKD). The level of renal S100A7 was associated with both the decline of renal function and the progression of renal fibrosis in CKD patients. Overexpressing S100A7a impaired fatty acid oxidation (FAO) and promoted lipid peroxidation in proximal tubular cells (PTCs). Mechanistically, S100A7a interacts with β-catenin, thereby preventing its ubiquitination and degradation by the β-TrCP-SCF complex, and in turn activated β-catenin signaling, downregulated the expression of PGC-1α. Additionally, S100A7a exacerbated lipid peroxidation via RAGE-p-ERK-NOX2 pathway. Specific deletion of S100a7a in tubular cells enhanced FAO and reduced lipid peroxidation, resulting in improved renal function and alleviation of renal fibrosis induced by unilateral ureteral obstruction and unilateral ischemia-reperfusion injury. Collectively, we delineate a previously unrecognized function of S100A7a in the progression of renal fibrosis.

Delivery of exogenous miR-19b by Wharton's Jelly Mesenchymal Stem Cells attenuates transplanted kidney ischemia/reperfusion injury by regulating cellular metabolism

Renal ischemia-reperfusion injury (IRI) frequently occurs following kidney transplantation, and exosomes derived from umbilical cord mesenchymal stem cells (WJ-MSC-Exos) have shown promise in treating IRI in transplanted kidneys. Our study delved into the potential mechanism of WJ-MSC-Exos in ameliorating IRI in transplanted kidneys, revealing that miR-19b is abundantly present in WJ-MSC-Exos. Both in vivo and in vitro experiments demonstrated that the absence of miR-19b abolished the protective effects of WJ-MSC-Exos against renal IRI. Mechanistically, miR-19b suppressed glycogen synthase kinase-3β (GSK3β) expression, thereby stabilizing PDXK protein through direct binding. Treatment with WJ-MSC-Exos led to reduced PDXK levels and enhanced pyridoxine accumulation, ultimately mitigating IRI in transplanted kidneys and I/R-induced HK2 cell apoptosis. These findings elucidate the underlying mechanism of WJ-MSC-Exos in alleviating IRI in transplanted kidneys, unveiling novel therapeutic targets for post-kidney transplantation IRI and providing a solid theoretical foundation for the clinical application of WJ-MSC-Exos in IRI treatment post-transplantation.

E3 ubiquitin ligase SYVN1 as a promising therapeutic target for diverse human diseases

Numerous studies conducted in recent years indicate that mammalian E3 ubiquitin ligases serve as key regulators in the maintenance of cellular homeostasis by targeting the ubiquitination of substrate proteins and activating downstream signaling pathways. SYVN1, an E3 ubiquitin ligase, is characterized by its significant functions in regulating various biological processes, including molecular mechanisms related to gene expression, signaling pathways, and cell death, among others. Consequently, SYVN1 plays a crucial role in both normal human physiology and the pathogenesis of various diseases, such as oncogenesis, cardiovascular disorders, immune regulation, skeletal anomalies, and neurological diseases. This review synthesizes recent findings regarding the physiological and pathophysiological roles of SYVN1, offering new insights into potential strategies for the prevention and treatment of human diseases, as well as suggesting avenues for future drug development. In this Review, we summarize the latest findings regarding the physiological and pathophysiological roles of SYVN1, elucidating the mechanisms by which SYVN1 can regulate the progression of various diseases in humans. These important findings provide new avenues for further investigation of SYVN1 protein, new insights into potential strategies to prevent and treat human diseases, and new directions for future drug development.

VDAC1-NF-κB/p65-mediated S100A16 contributes to myocardial ischemia/reperfusion injury by regulating oxidative stress and inflammatory response via calmodulin/CaMKK2/AMPK pathway

Myocardial injury triggers intense inflammatory reactions and oxidative stress responses. S100 calcium-binding protein A16 (S100A16), a multi-functional calcium (Ca2+)-binding protein, participates in inflammatory responses and contributes to ischemia/reperfusion (I/R) injury. Nevertheless, the precise mechanism by which S100A16 operates in myocardial I/R injury remains uncertain. Cardiac I/R injury was produced by ligation/release of the left anterior descending artery, and mouse cardiac cells were subjected to hypoxia/reoxygenation (H/R) to determine the biological effects in vitro. We demonstrated that S100A16 was upregulated in the ischemic hearts and cardiac cells after I/R and H/R injury. Adenovirus-mediated S100A16 inhibition led to a considerable improvement in cardiac function with a reduced infarct size, accompanied by a reduction in cardiomyocyte apoptosis. Similar effects of S100A16 inhibition on inflammation and reactive oxygen species (ROS) production were observed in cultured cardiomyocytes. Importantly, we showed that I/R and H/R treatment upregulated the expression of voltage-dependent anion channel 1 (VDAC1), which subsequently activated NF-κB/p65 to facilitate the binding of NF-κB/p65 to the S100A16 promoter, thereby activating the transcription and expression of S100A16. Mechanically, S100A16 responded to increasing Ca2+ and interacted with calmodulin (CaM) to regulate the activation of calcium/calmodulin-dependent protein kinase 2 (CAMKK2)/AMPK pathway. In conclusion, VDAC1 sustained the NF-κB p65 pathway activation to elicit increased S100A16 expression, contributing to myocardial damage and heart failure post-I/R via the CaM/CaMKK2/AMPK pathway. This study revealed a crucial role of the VDAC1-S100A16 axis in the process of myocardial I/R injury, providing novel molecular targets for the treatment of cardiac conditions associated with I/R injury.

Gut microbiota regulates oxidative stress and inflammation: a double-edged sword in renal fibrosis

Gut microbiota is a complex and dynamic system that plays critical roles in human health and various disease. Progressive chronic kidney disease (CKD) suggests that patients irreversibly progress to end-stage kidney disease and need renal replacement treatments, including dialysis and transplantation. Ample evidence indicates that local oxidative stress and inflammation play pivotal roles in the pathogenesis and progression of CKD and dysbiosis of gut microbiota. CKD is always accompanied by intestinal inflammation and oxidative stress, which lead to rapid systemic translocation of bacterial-derived uraemic toxins, including indoxyl sulphate, phenyl sulphate and indole-3-acetic acid, and the consequent development and aggravation of renal fibrosis. Although inflammation and oxidative stress have been extensively discussed, there is a paucity of reports on the effects of gut microbiota on renal fibrosis and gut microbiota mediation of oxidative stress and inflammation. This review provides an overview of gut microbiota on inflammation and oxidative stress in renal fibrosis, briefly discusses regulation of the gut flora using microecological preparations and natural products, such as resveratrol, curcumin and emodin as treatments for CKD, and provides a clear pathophysiological rationale for the design of promising therapeutic strategies.

Status and role of the ubiquitin-proteasome system in renal fibrosis

The ubiquitin-proteasome system (UPS) is a basic regulatory mechanism in cells that is essential for maintaining cell homeostasis, stimulating signal transduction, and determining cell fate. These biological processes require coordinated signaling cascades across members of the UPS to achieve substrate ubiquitination and deubiquitination. The role of the UPS in fibrotic diseases has attracted widespread attention, and the aberrant expression of UPS members affects the fibrosis process. In this review, we provide an overview of the UPS and its relevance for fibrotic diseases. Moreover, for the first time, we explore in detail how the UPS promotes or inhibits renal fibrosis by regulating biological processes such as signaling pathways, inflammation, oxidative stress, and the cell cycle, emphasizing the status and role of the UPS in renal fibrosis. Further research on this system may reveal new strategies for preventing renal fibrosis.

Glycogen synthase kinase-3β: A multifaceted player in ischemia-reperfusion injury and its therapeutic prospects

Ischemia-reperfusion injury (IRI) results in irreversible metabolic dysfunction and structural damage to tissues or organs, posing a formidable challenge in the field of organ implantation, cardiothoracic surgery, and general surgery. Glycogen synthase kinase-3β (GSK-3β) a multifunctional serine/threonine kinase, is involved in a variety of biological processes, including cell proliferation, apoptosis, and immune response. Phosphorylation of its tyrosine 216 and serine 9 sites positively and negatively regulates the activation and inactivation of the enzyme. Significantly, inhibition or inactivation of GSK-3β provides protection against IRI, making it a viable target for drug development. Though numerous GSK-3β inhibitors have been identified to date, the development of therapeutic treatments remains a considerable distance away. In light of this, this review summarizes the complicated network of GSK-3β roles in IRI. First, we provide an overview of GSK-3β's basic background. Subsequently, we briefly review the pathological mechanisms of GSK-3β in accelerating IRI, and highlight the latest progress of GSK-3β in multiorgan IRI, encompassing heart, brain, kidney, liver, and intestine. Finally, we discuss the current development of GSK-3β inhibitors in various organ IRI, offering a thorough and insightful reference for GSK-3β as a potential target for future IRI therapy.

Proximal tubular FHL2, a novel downstream target of hypoxia inducible factor 1, is a protector against ischemic acute kidney injury

Four-and-a-half LIM domains protein 2 (FHL2) is an adaptor protein that may interact with hypoxia inducible factor 1α (HIF-1α) or β-catenin, two pivotal protective signaling in acute kidney injury (AKI). However, little is known about the regulation and function of FHL2 during AKI. We found that FHL2 was induced in renal tubular cells in patients with acute tubular necrosis and mice model of ischemia-reperfusion injury (IRI). In cultured renal proximal tubular cells (PTCs), hypoxia induced FHL2 expression and promoted the binding of HIF-1 to FHL2 promoter. Compared with control littermates, mice with PTC-specific deletion of FHL2 gene displayed worse renal function, more severe morphologic lesion, more tubular cell death and less cell proliferation, accompanying by downregulation of AQP1 and Na, K-ATPase after IRI. Consistently, loss of FHL2 in PTCs restricted activation of HIF-1 and β-catenin signaling simultaneously, leading to attenuation of glycolysis, upregulation of apoptosis-related proteins and downregulation of proliferation-related proteins during IRI. In vitro, knockdown of FHL2 suppressed hypoxia-induced activation of HIF-1α and β-catenin signaling pathways. Overexpression of FHL2 induced physical interactions between FHL2 and HIF-1α, β-catenin, GSK-3β or p300, and the combination of these interactions favored the stabilization and nuclear translocation of HIF-1α and β-catenin, enhancing their mediated gene transcription. Collectively, these findings identify FHL2 as a direct downstream target gene of HIF-1 signaling and demonstrate that FHL2 could play a critical role in protecting against ischemic AKI by promoting the activation of HIF-1 and β-catenin signaling through the interactions with its multiple protein partners.

HIF-1α participates in the regulation of S100A16-HRD1-GSK3β/CK1α pathway in renal hypoxia injury

S100 calcium-binding protein 16 (S100A16) is implicated in both chronic kidney disease (CKD) and acute kidney injury (AKI). Previous research has shown that S100A16 contributes to AKI by facilitating the ubiquitylation and degradation of glycogen synthase kinase 3β (GSK3β) and casein kinase 1α (CK1α) through the activation of HMG-CoA reductase degradation protein 1 (HRD1). However, the mechanisms governing S100A16-induced HRD1 activation and the upregulation of S100A16 expression in renal injury are not fully understood. In this study, we observed elevated expression of Hypoxia-inducible Factor 1-alpha (HIF-1α) in the kidneys of mice subjected to ischemia-reperfusion injury (IRI). S100A16 deletion attenuated the increased HIF-1α expression induced by IRI. Using a S100A16 knockout rat renal tubular epithelial cell line (NRK-52E cells), we found that S100A16 knockout effectively mitigated apoptosis during hypoxic reoxygenation (H/R) and cell injury induced by TGF-β1. Our results revealed that H/R injuries increased both protein and mRNA levels of HIF-1α and HRD1 in renal tubular cells. S100A16 knockout reversed the expressions of HIF-1α and HRD1 under H/R conditions. Conversely, S100A16 overexpression in NRK-52E cells elevated HIF-1α and HRD1 levels. HIF-1α overexpression increased HRD1 and β-catenin while decreasing GSK-3β. HIF-1α inhibition restored HRD1 and β-catenin upregulation and GSK-3β downregulation by cellular H/R injury. Notably, Chromatin immunoprecipitation (ChIP) and luciferase reporter assays demonstrated HIF-1α binding signals on the HRD1 promoter, and luciferase reporter gene assays confirmed HIF-1α's transcriptional regulation of HRD1. Additionally, we identified Transcription Factor AP-2 Beta (TFAP2B) as the upregulator of S100A16. ChIP and luciferase reporter assays confirmed TFAP2B as a transcription factor for S100A16. In summary, this study identifies TFAP2B as the transcription factor for S100A16 and demonstrates HIF-1α regulation of HRD1 transcription within the S100A16-HRD1-GSK3β/CK1α pathway during renal hypoxia injury. These findings provide crucial insights into the molecular mechanisms of kidney injury, offering potential avenues for therapeutic intervention.

Dysregulated SYVN1 promotes CAV1 protein ubiquitination and accentuates ischemic stroke

BACKGROUND

Stroke is a major cause of death and severe disability, and there remains a substantial need for the development of therapeutic agents for neuroprotection in acute ischemic stroke (IS) to protect the brain against damage before and during recanalization. Caveolin-1 (CAV1), an integrated protein that is located at the caveolar membrane, has been reported to exert neuroprotective effects during IS. Nevertheless, the mechanism remains largely unknown. Here, we explored the upstream modifiers of CAV1 in IS.

METHODS

E3 ubiquitin ligases of CAV1 that are differentially expressed in IS were screened using multiple databases. The transcription factor responsible for the dysregulation of E3 ubiquitin-protein ligase synoviolin (SYVN1) in IS was predicted and verified. Genetic manipulations by lentiviral vectors were applied to investigate the effects of double-strand-break repair protein rad21 homolog (RAD21), SYVN1, and CAV1 in a middle cerebral artery occlusion (MCAO) mouse model and mouse HT22 hippocampal neurons induced by oxygen-glucose deprivation (OGD).

RESULTS

SYVN1 was highly expressed in mice with MCAO, and knockdown of SYVN1 alleviated IS injury in mice, as evidenced by limited infarction volume, the lower water content in the brain, and repressed apoptosis and inflammatory response. RAD21 inhibited the transcription of SYVN1, thereby reducing the ubiquitination modification of CAV1. Overexpression of RAD21 elicited a neuroprotective role as well in mice with MCAO and HT22 induced with OGD, which was overturned by SYVN1.

CONCLUSION

Transcriptional repression of SYVN1 by RAD21 alleviates IS in mice by reducing ubiquitination modification of CAV1.

HRD1-induced TMEM2 ubiquitination promotes ER stress-mediated apoptosis through a non-canonical pathway in intestinal ischemia/reperfusion

Intestinal ischemia/reperfusion (I/R) injury is a typical pathological course in the clinic with a high morbidity rate. Recent research has pointed out the critical role of ubiquitination during the occurrence and development of intestinal I/R by precisely mediating protein quality control and function. Here, we conducted an integrated multiomic analysis to identify critical ubiquitination-associated molecules in intestinal I/R and identified endoplasmic reticulum-located HRD1 as a candidate molecule. During intestinal I/R, excessive ER stress plays a central role by causing apoptotic pathway activation. In particular, we found that ER stress-mediated apoptosis was mitigated by HRD1 knockdown in intestinal I/R mice. Mechanistically, TMEM2 was identified as a new substrate of HRD1 in intestinal I/R by mass spectrometry analysis, which has a crucial role in attenuating apoptosis and promoting non-canonical ER stress resistance. A strong negative correlation was found between the protein levels of HRD1 and TMEM2 in human intestinal ischemia samples. Specifically, HRD1 interacted with the lysine 42 residue of TMEM2 and reduced its stabilization by K48-linked polyubiquitination. Furthermore, KEGG pathway analysis revealed that TMEM2 regulated ER stress-mediated apoptosis in association with the PI3k/Akt signaling pathway rather than canonical ER stress pathways. In summary, HRD1 regulates ER stress-mediated apoptosis through a non-canonical pathway by ubiquitinating TMEM2 and inhibiting PI3k/Akt activation during intestinal I/R. The current study shows that HRD1 is an intestinal I/R critical regulator and that targeting the HRD1/TMEM2 axis may be a promising therapeutic approach.

GSK3β: A ray of hope for the treatment of diabetic kidney disease

Diabetic kidney disease (DKD), a major microvascular complication of diabetes, is characterized by its complex pathogenesis, high risk of chronic renal failure, and lack of effective diagnosis and treatment methods. GSK3β (glycogen synthase kinase 3β), a highly conserved threonine/serine kinase, was found to activate glycogen synthase. As a key molecule of the glucose metabolism pathway, GSK3β participates in a variety of cellular activities and plays a pivotal role in multiple diseases. However, these effects are not only mediated by affecting glucose metabolism. This review elaborates on the role of GSK3β in DKD and its damage mechanism in different intrinsic renal cells. GSK3β is also a biomarker indicating the progression of DKD. Finally, the protective effects of GSK3β inhibitors on DKD are also discussed.

Imbalanced lipid homeostasis caused by membrane αKlotho deficiency contributes to the acute kidney injury to chronic kidney disease transition

After acute kidney injury (AKI), renal tubular epithelial cells (RTECs) are pathologically characterized by intracellular lipid droplet (LD) accumulation, which are involved in RTEC injury and kidney fibrosis. However, its pathogenesis remains incompletely understood. The protein, αKlotho, primarily expressed in RTECs, is well known as an anti-aging hormone wielding versatile functions, and its membrane form predominantly acts as a co-receptor for fibroblast growth factor 23. Here, we discovered a connection between membrane αKlotho and intracellular LDs in RTECs. Fluorescent fatty acid (FA) pulse-chase assays showed that membrane αKlotho deficiency in RTECs, as seen in αKlotho homozygous mutated (kl/kl) mice or in mice with ischemia-reperfusion injury (IRI)-induced AKI, inhibited FA mobilization from LDs by impairing adipose triglyceride lipase (ATGL)-mediated lipolysis and lipophagy. This resulted in LD accumulation and FA underutilization. IRI-induced alterations were more striking in αKlotho deficiency. Mechanistically, membrane αKlotho deficiency promoted E3 ligase peroxin2 binding to ubiquitin-conjugating enzyme E2 D2, resulting in ubiquitin-mediated degradation of ATGL which is a common molecular basis for lipolysis and lipophagy. Overexpression of αKlotho rescued FA mobilization by preventing ATGL ubiquitination, thereby lessening LD accumulation and fibrosis after AKI. This suggests that membrane αKlotho is indispensable for the maintenance of lipid homeostasis in RTECs. Thus, our study identified αKlotho as a critical regulator of lipid turnover and homeostasis in AKI, providing a viable strategy for preventing tubular injury and the AKI-to-chronic kidney disease transition.

The Proteome Profile of Olfactory Ecto-Mesenchymal Stem Cells-Derived from Patients with Familial Alzheimer's Disease Reveals New Insights for AD Study

Alzheimer's disease (AD), the most common neurodegenerative disease and the first cause of dementia worldwide, has no effective treatment, and its pathological mechanisms are not yet fully understood. We conducted this study to explore the proteomic differences associated with Familial Alzheimer's Disease (FAD) in olfactory ecto-mesenchymal stem cells (MSCs) derived from PSEN1 (A431E) mutation carriers compared with healthy donors paired by age and gender through two label-free liquid chromatography-mass spectrometry approaches. The first analysis compared carrier 1 (patient with symptoms, P1) and its control (healthy donor, C1), and the second compared carrier 2 (patient with pre-symptoms, P2) with its respective control cells (C2) to evaluate whether the protein alterations presented in the symptomatic carrier were also present in the pre-symptom stages. Finally, we analyzed the differentially expressed proteins (DEPs) for biological and functional enrichment. These proteins showed impaired expression in a stage-dependent manner and are involved in energy metabolism, vesicle transport, actin cytoskeleton, cell proliferation, and proteostasis pathways, in line with previous AD reports. Our study is the first to conduct a proteomic analysis of MSCs from the Jalisco FAD patients in two stages of the disease (symptomatic and presymptomatic), showing these cells as a new and excellent in vitro model for future AD studies.

S100 Calcium Binding Protein A16 Promotes Cell Proliferation by triggering LATS1 ubiquitin degradation mediated by CUL4A ligase to inhibit Hippo pathway in Glioma development

Background: S100 Calcium Binding Protein A16 (S100A16), a novel member of S100 protein family, is linked to tumorigenic processes and abundantly expressed in CNS tissues. Our study aimed to explore the biological function and possible mechanism of S100A16 in the progression of glioma. Methods: Sequence data of S100A16 and survival prognosis of glioma patients were initially analyzed using public databases. Glioma tissues were collected to examine S100A16 expression levels. Glioma cell lines and nude mice were subjected to in vitro and in vivo functional experiments. Western blot, immunofluorescence (IF), immunoprecipitation (IP) and ubiquitination assays were done to further elucidate the underlying mechanism. Results: This study firstly revealed that S100A16 was markedly up-regulated in glioma, and patients with higher S100A16 levels have a shorter survival time. S100A16 overexpression promoted the proliferation, invasion and migration of glioma cells, and the tumor formation of nude mice. Importantly, we identified S100A16 as a negative regulator of the Hippo pathway which could decrease LATS1 expression levels, promote the YAP nuclear import and initiate the downstream target genes CYR61 and CTGF. Moreover, our data showed that S100A16 destabilized LATS1 protein by inducing the CUL4A-mediated LATS1 ubiquitination degradation. Conclusions: This study demonstrated a vital biological role of S100A16 in glioma progression mechanism by promoting CUL4A-mediated LATS1 ubiquitination to inhibit Hippo signaling pathway. S100A16 could be a novel biomarker and treatment option for glioma patients.