The CPLANE protein Intu protects kidneys from ischemia-reperfusion injury by targeting STAT1 for degradation

CPLANE protein INTU regulates growth and patterning of the mouse lungs through cilia-dependent Hh signaling

Congenital lung malformations are fatal at birth in their severe forms. Prevention and early intervention of these birth defects require a comprehensive understanding of the molecular mechanisms of lung development. We find that the loss of inturned (Intu), a cilia and planar polarity effector gene, severely disrupts growth and branching morphogenesis of the mouse embryonic lungs. Consistent with our previous results indicating an important role for Intu in ciliogenesis and hedgehog (Hh) signaling, we find greatly reduced number of primary cilia in both the epithelial and mesenchymal tissues of the lungs. We also find significantly reduced expression of Gli1 and Ptch1, direct targets of Hh signaling, suggesting disruption of cilia-dependent Hh signaling in Intu mutant lungs. An agonist of the Hh pathway activator, smoothened, increases Hh target gene expression and tubulogenesis in explanted wild type, but not Intu mutant, lungs, suggesting impaired Hh signaling response underlying lung morphogenetic defects in Intu mutants. Furthermore, removing both Gli2 and Intu completely abolishes branching morphogenesis of the lung, strongly supporting a mechanism by which Intu regulates lung growth and patterning through cilia-dependent Hh signaling. Moreover, a transcriptomics analysis identifies around 200 differentially expressed genes (DEGs) in Intu mutant lungs, including known Hh target genes Gli1, Ptch1/2 and Hhip. Genes involved in muscle differentiation and function are highly enriched among the DEGs, consistent with an important role of Hh signaling in airway smooth muscle differentiation. In addition, we find that the difference in gene expression between the left and right lungs diminishes in Intu mutants, suggesting an important role of Intu in asymmetrical growth and patterning of the mouse lungs.

Planar Cell Polarity Signaling: Coordinated Crosstalk for Cell Orientation

The planar cell polarity (PCP) system is essential for positioning cells in 3D networks to establish the proper morphogenesis, structure, and function of organs during embryonic development. The PCP system uses inter- and intracellular feedback interactions between components of the core PCP, characterized by coordinated planar polarization and asymmetric distribution of cell populations inside the cells. PCP signaling connects the anterior-posterior to left-right embryonic plane polarity through the polarization of cilia in the Kupffer's vesicle/node in vertebrates. Experimental investigations on various genetic ablation-based models demonstrated the functions of PCP in planar polarization and associated genetic disorders. This review paper aims to provide a comprehensive overview of PCP signaling history, core components of the PCP signaling pathway, molecular mechanisms underlying PCP signaling, interactions with other signaling pathways, and the role of PCP in organ and embryonic development. Moreover, we will delve into the negative feedback regulation of PCP to maintain polarity, human genetic disorders associated with PCP defects, as well as challenges associated with PCP.

From Primary Cilia and Planar Cell Polarity to Kidney Injury and Repair

Almost every cell in the kidney, including renal tubular epithelial cells, has a primary cilium, which is a membrane-bound, hair-like structure protruding from the cellular surface. Dysfunction of primary cilia has been linked to a wide spectrum of human genetic diseases, termed ciliopathies. Planar cell polarity (PCP) refers to the coordinated alignment of cells along the cell sheet or tissue plane, a fundamental process in embryo development and organogenesis. Interestingly, there is evidence that primary cilium and PCP are interconnected. However, very limited is known about the involvement of cilia and PCP in kidney injury and repair. By using cell and mouse models, we have demonstrated a protective role of primary cilia in acute kidney injury. Mechanistically, we unveiled a reciprocal promoting relationship between cilia and autophagy in kidney tubular cells, and, accordingly, cilia may protect tubular cells by enhancing autophagy. Our recent studies further demonstrated that PCP dysfunction exaggerates acute kidney injury and may also contribute to maladaptive kidney repair after acute kidney injury. These findings provide a novel dimension to further understanding kidney injury and repair from the standpoint of cell biology.

Tubular cell senescence promotes maladaptive kidney repair and chronic kidney disease after cisplatin nephrotoxicity

Cisplatin is a widely used chemotherapy drug; however, it induces both acute and chronic kidney diseases (CKD) in patients with cancer. The pathogenesis of cisplatin-induced CKD is unclear, and effective renoprotective approaches are not available. Here, we report that repeated low-dose cisplatin (RLDC) treatment of C57BL/6 mice induced chronic cellular senescence in kidney tubules, accompanied with tubular degeneration and profibrotic phenotype transformation that culminated in maladaptive repair and renal fibrosis. Suppression of tubular senescence by senolytic drugs ABT-263 and Fisetin attenuated renal fibrosis and improved tubular repair, as indicated by restoration of tubular regeneration and renal function. In vitro, RLDC also induced senescence in mouse proximal tubular (BUMPT) cells. ABT-263 eliminated senescent BUMPT cells following RLDC treatment, reversed the profibrotic phenotype of the cells, and increased their clonogenic activity. Moreover, ABT-263 alleviated the paracrine effect of RLDC-treated BUMPT cells on fibroblasts for fibrosis. Consistently, knockdown of p16 suppressed post-RLDC senescence and fibrotic changes in BUMPT cells and alleviated their paracrine effects on renal fibroblast proliferation. These results indicate that persistent induction of tubular senescence plays an important role in promoting cisplatin-induced CKD. Targeting senescent tubular cells may be efficient for improvement of kidney repair and for the prevention and treatment of cisplatin-induced CKD.

Downregulation of G protein-coupled receptor kinase 4 protects against kidney ischemia-reperfusion injury

Ischemia/reperfusion injury of the kidney is associated with high morbidity and mortality, and treatment of this injury remains a challenge. G protein-coupled receptor kinase 4 (GRK4) plays a vital role in essential hypertension and myocardial infarction, but its function in kidney ischemia/reperfusion injury remains undetermined. Among the GRK subtypes (GRK2-6) expressed in kidneys, the increase in GRK4 expression was much more apparent than that of the other four GRKs 24 hours after injury and was found to accumulate in the nuclei of injured mouse and human renal tubule cells. Gain- and loss-of-function experiments revealed that GRK4 overexpression exacerbated acute kidney ischemia/reperfusion injury, whereas kidney tubule-specific knockout of GRK4 decreased injury-induced kidney dysfunction. Necroptosis was the major type of tubule cell death mediated by GRK4, because GRK4 significantly increased receptor interacting kinase (RIPK)1 expression and phosphorylation, subsequently leading to RIPK3 and mixed lineage kinase domain-like protein (MLKL) phosphorylation after kidney ischemia/reperfusion injury, but was reversed by necrostatin-1 pretreatment (an RIPK1 inhibitor). Using co-immunoprecipitation, mass spectrometry, and siRNA screening studies, we identified signal transducer and activator of transcription (STAT)1 as a GRK4 binding protein, which co-localized with GRK4 in the nuclei of renal tubule cells. Additionally, GRK4 phosphorylated STAT1 at serine 727, whose inactive mutation effectively reversed GRK4-mediated RIPK1 activation and tubule cell death. Kidney-targeted GRK4 silencing with nanoparticle delivery considerably ameliorated kidney ischemia/reperfusion injury. Thus, our findings reveal that GRK4 triggers necroptosis and aggravates kidney ischemia/reperfusion injury, and its downregulation may provide a promising therapeutic strategy for kidney protection.

Deficiency of the Planar Cell Polarity Protein Intu Delays Kidney Repair and Suppresses Renal Fibrosis after Acute Kidney Injury

Planar cell polarity (PCP), a process of coordinated alignment of cell polarity across the tissue plane, may contribute to the repair of renal tubules after kidney injury. Intu is a key effector protein of PCP. Herein, conditional knockout (KO) mouse models that ablate Intu specifically from kidney tubules (Intu KO) were established. Intu KO mice and wild-type littermates were subjected to unilateral renal ischemia/reperfusion injury (IRI) or unilateral ureteral obstruction. Kidney repair was evaluated by histologic, biochemical, and immunohistochemical analyses. In vitro, scratch wound healing was examined in Intu-knockdown and control renal tubular cells. Ablation of Intu in renal tubules delayed kidney repair and ameliorated renal fibrosis after renal IRI. Intu KO mice had less renal fibrosis during unilateral ureteral obstruction. Mechanistically, Intu KO kidneys had less senescence but higher levels of cell proliferation and apoptosis during kidney repair after renal IRI. In vitro, Intu knockdown suppressed scratch wound healing in renal tubular cells, accompanied by the abnormality of centrosome orientation. Together, the results provide the first evidence for the involvement of PCP in tubular repair after kidney injury, shedding light on new strategies for improving kidney repair and recovery.

CD44 Receptor-Targeted and Reactive Oxygen Species-Responsive H2S Donor Micelles Based on Hyaluronic Acid for the Therapy of Renal Ischemia/Reperfusion Injury

For the therapy attenuating renal ischemia-reperfusion (IR) injury, a novel drug delivery system was urgently needed, which could precisely deliver drugs to the pathological renal tissue. Here, we have prepared new nanomaterials with a reactive oxygen species (ROS)-responsive hydrogen sulfide (H₂S) donor and hyaluronic acid that targets CD44 receptor. The novel material was synthesized and characterized via related experiments. Then, rapamycin was loaded, which inhibited kidney damage. In the in vitro study, we found that the micelles had ROS-responsiveness, biocompatibility, and cell penetration. In addition, the experimental results showed that the intracellular H₂S concentration after administration was threefold higher than that of the control group. The western blot assay revealed that they have anti-inflammatory effects via H₂S donor blocking the NF-κB signaling pathway. Consequently, the rising CD44 receptor-targeting and ROS-sensitive H₂S donor micelles would provide a promising way for renal IR injury. This work provides a strategy for improving ischemia/reperfusion injury for pharmaceuticals.

Biomechanical regulation of planar cell polarity in endothelial cells

Cell polarity refers to the uneven distribution of certain cytoplasmic components in a cell with a spatial order. The planar cell polarity (PCP), the cell aligns perpendicular to the polar plane, in endothelial cells (ECs) has become a research hot spot. The planar polarity of ECs has a positive significance on the regulation of cardiovascular dysfunction, pathological angiogenesis, and ischemic stroke. The endothelial polarity is stimulated and regulated by biomechanical force. Mechanical stimuli promote endothelial polarization and make ECs produce PCP to maintain the normal physiological and biochemical functions. Here, we overview recent advances in understanding the interplay and mechanism between PCP and ECs function involved in mechanical forces, with a focus on PCP signaling pathways and organelles in regulating the polarity of ECs. And then showed the related diseases caused by ECs polarity dysfunction. This study provides new ideas and therapeutic targets for the treatment of endothelial PCP-related diseases.

HSP90 Mediates IFNγ-Induced Adaptive Resistance to Anti-PD-1 Immunotherapy

SIGNIFICANCE

This study reveals an HSP90-centric, iron-modulated mechanism that confers immunosuppression, offering potential therapeutic targets for interfering with acquired resistance to the most prevalent anticancer immunotherapies.

Prenatal Diagnosis of Combined Maternal 4q Interstitial Deletion and Paternal 15q Microduplication

The 4q deletion syndrome is a well-known rare genetic condition caused by partial, terminal, or interstitial deletion in the long arm (q) of chromosome 4. The phenotype of this syndrome shows a broad spectrum of clinical manifestations due to the great variability in the size and location of the deletion. In the literature, the mostly terminal deletions of chromosome 4q and the relative phenotypes are described, while the interstitial deletions of the long arm of chromosome 4 are rarely cited. Here, we report on a female fetus presenting no abnormal ultrasound evidence but with multiple chromosome aberrations. Comparative genomic hybridization (aCGH) revealed an interstitial 10.09 Mb deletion at the chromosome at the region of 4q28, arr[hg19] 4q28.1q28.3 (124068262_134158728)x1 combined with a 386.81 Kb microduplication at chromosome 15q11.1, arr[hg19] 15.11 (20249932_20636742)x3. At birth, and after 11 months, the baby was confirmed healthy and normal. The identification of this case allows for a deeper understanding of 4q syndrome and provides an explanation for the wide genetic/phenotypic spectrum of this pathology. This report can provide a reference for prenatal diagnosis and genetic counseling in patients who have similar cytogenetic abnormalities, and underlines the importance of reporting unusual variant chromosomes for diagnostic genetic purposes.

Effects of stem cell-derived exosomes on neuronal apoptosis and inflammatory cytokines in rats with cerebral ischemia-reperfusion injury via PI3K/AKT pathway-mediated mitochondrial apoptosis

OBJECTIVE

This study aimed to investigate the effects of stem cell-derived exosomes (SC-Exos) on learning, memory, and neuronal apoptosis in rats with cerebral ischemia-reperfusion injury and to determine whether SC-Exos exert their effects via phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) pathway-mediated mitochondrial pathways of apoptosis.

MATERIALS AND METHODS

Eighty rats were randomly allocated to control, model, SC-Exos, and PI3K inhibitor groups. A model of focal cerebral ischemia-reperfusion was established using the improved Longa method. Expression of interleukin-1α (IL-1α), interleukin-2 (IL-2), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) were compared in the brains and serum of each group. The expressions of Bcl-2, Bax, cleaved-caspase-3, cleaved-caspase-9, cytochrome C (CytC), PI3K, and AKT-related genes and proteins were evaluated by real-time quantitative polymerase chain reaction and western blotting.

RESULTS

The SC-Exos-group exhibited more novel entries, less latency for the novel arm, and fewer entries into the starting arm and other arms than the model group (p<.05). Lower expression of the inflammatory cytokines IL-1α, IL-2, and TNF-α and higher expression of IFN-γ were observed in the SC-Exos group than in the model group. TdT-mediated dUTP nick end labeling (TUNEL) assay showed that lower neural cell apoptosis rate and expression of Bax, cleaved-caspase-3, cleaved-caspase-9, CytC, PI3K, and AKT mRNA and proteins and higher expression of Bcl-2 mRNA and protein were observed in the SC-Exos group than in the model group (p<.05).

CONCLUSIONS

SC-Exos can significantly ameliorate brain injury caused by cerebral ischemia-reperfusion. The mechanism may be a novel therapeutic target for ischemia-reperfusion injury.

The semaphorin 4A-neuropilin 1 axis alleviates kidney ischemia reperfusion injury by promoting the stability and function of regulatory T cells

Previous studies have suggested the role of CD4⁺Foxp3⁺ regulatory T cells (Tregs) in protection against kidney ischemia reperfusion injury via their immunosuppressive properties. Unfortunately, the associated mechanisms of Tregs in kidney ischemia reperfusion injury have not been fully elucidated. Semaphorin 4A (Sema4A) is essential for maintaining the immunosuppressive capacity of Tregs in tumors. However, whether Sema4A can alleviate kidney ischemia reperfusion injury through Tregs has not yet been demonstrated. Here, we investigated the effect and mechanism of Sema4A on the development of kidney ischemia reperfusion injury. Administration of recombinant human Sema4A-Fc chimera protein prior to ischemia reperfusion injury promoted the expansion and function of Tregs and decreased the accumulation of neutrophils and proinflammatory macrophages thereby attenuating functional and histological injury of the injured kidneys. Depletion of Tregs abrogated the protective effect of Sema4A on kidney ischemia reperfusion injury, suggesting Tregs as the main target cell type for Sema4A in the development of this injury. Mechanistically, Sema4A bound to neuropilin 1 (Nrp1), a cell surface receptor for Sema4A and other ligands and a key regulator of Tregs, which then promoted recruitment of phosphatase and tensin homologue and suppressed the Akt-mTOR pathway in Foxp3^Cre mice but not in Nrp1^f/fFoxp3^Cre mice. Consistently, Treg-specific deletion of Nrp1 blocked the effect of Sema4A on the expansion and function of Treg cells. Thus, our results demonstrate that the Sema4A-Nrp1 axis alleviates the development of ischemia reperfusion injury by promoting the stability and function of Tregs in mouse kidneys.

Decreased IFT88 expression with primary cilia shortening causes mitochondrial dysfunction in cisplatin-induced tubular injury

The relevance of primary cilia shortening in kidney disease and its pathomechanism are largely unknown. Tubular damage in acute kidney injury (AKI) is strongly associated with mitochondrial dysfunction. Thus, we investigated the interaction between primary cilia and mitochondria in cisplatin-induced AKI mouse models. We observed that the expression of intraflagellar transport 88 (IFT88), a ciliary maintenance protein, was decreased in the renal cortex following tubular damage due to cisplatin-induced AKI. This result was consistent with the decreased IFT88 expression in cisplatin-treated RPTEC/TERT1 cells (human primary proximal tubular cells) parallel to the shortening of primary cilia, suggesting a causative link between tubular damage and IFT88-mediated cilia regulation. To address the effect of impaired primary cilia with decreased IFT88 expression on tubular function, RPTEC/TERT1 cells treated with cisplatin and knocked down for IFT88 using siRNA (IFT88-KD) were assessed for phenotypic changes and mitochondrial metabolic function. Both cisplatin and IFT88-KD caused primary cilia shortening, downregulated mitochondrial oxidative phosphorylation capacity, and had defective fatty acid oxidation and decreased ATP production. Furthermore, IFT88 overexpression enhanced mitochondrial respiration, which partially counteracted cisplatin-induced defective fatty acid oxidation. These results are indicative of the contribution of IFT88 to mitochondrial homeostasis. Our findings suggest that tubular mitochondrial dysfunction in cisplatin-induced AKI is mediated, at least in part, by a decrease in IFT88 expression with primary cilia shortening. That is, tubular mitochondrial damage followed by tubular injury in AKI may occur through alteration of IFT88 expression and subsequent ciliary shortening in tubular cells.NEW & NOTEWORTHY Here, we demonstrated organelle cross-talk between primary cilia and mitochondria of proximal tubular cells in cisplatin-induced acute kidney injury. The primary cilia-mitochondria interaction may open new avenues for the development of novel therapeutic approaches in the treatment of acute kidney injury.

Study of the Active Components and Molecular Mechanism of Tripterygium wilfordii in the Treatment of Diabetic Nephropathy

We aimed to explore the active ingredients and molecular mechanism of Tripterygium wilfordii (TW) in the treatment of diabetic nephropathy (DN) through network pharmacology and molecular biology. First, the active ingredients and potential targets of TW were obtained through the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) and related literature materials, and Cytoscape 3.7.2 software was used to construct the active ingredient-target network diagram of TW. Second, the target set of DN was obtained through the disease database, and the potential targets of TW in the treatment of DN were screened through a Venn diagram. A protein interaction network diagram (PPI) was constructed with the help of the String platform and Cytoscape 3.7.2. Third, the ClueGO plug-in tool was used to enrich the GO biological process and the KEGG metabolic pathway. Finally, molecular docking experiments and cell pathway analyses were performed. As a result, a total of 52 active ingredients of TW were screened, and 141 predicted targets and 49 target genes related to DN were identified. The biological process of GO is mediated mainly through the regulation of oxygen metabolism, endothelial cell proliferation, acute inflammation, apoptotic signal transduction pathway, fibroblast proliferation, positive regulation of cyclase activity, adipocyte differentiation and other biological processes. KEGG enrichment analysis showed that the main pathways involved were AGE-RAGE, vascular endothelial growth factor, HIF-1, IL-17, relaxin signalling pathway, TNF, Fc epsilon RI, insulin resistance and other signaling pathways. It can be concluded that TW may treat DN by reducing inflammation, reducing antioxidative stress, regulating immunity, improving vascular disease, reducing insulin resistance, delaying renal fibrosis, repairing podocytes, and reducing cell apoptosis, among others, with multicomponent, multitarget and multisystem characteristics.

Involvement of GPX4 in irisin's protection against ischemia reperfusion-induced acute kidney injury

Ischemia reperfusion (I/R)-induced acute kidney injury (AKI) is a common and serious condition. Irisin, an exercise-induced hormone, improves mitochondrial function and reduces reactive oxygen species (ROS) production. Glutathione peroxidase 4 (GPX4) is a key regulator of ferroptosis and its inactivation aggravates renal I/R injury by inducing ROS production. However, the effect of irisin on GPX4 and I/R-induced AKI is still unknown. To study this, male adult mice were subjected to renal I/R by occluding bilateral renal hilum for 30 min, which was followed by 24 hr reperfusion. Our results showed serum irisin levels were decreased in renal I/R mice. Irisin (250 μg/kg) treatment alleviated renal injury, downregulated inflammatory response, improved mitochondrial function, and reduced ER stress and oxidative stress after renal I/R, which were associated with upregulation of GPX4. Treated with RSL3 (a GPX4 inhibitor) abolished irisin's protective effect. Thus, irisin attenuates I/R-induced AKI through upregulating GPX4.

Hexa-Longin domain scaffolds for inter-Rab signalling

Summary

CPLANE is a protein complex required for assembly and maintenance of primary cilia. It contains several proteins, such as INTU, FUZ, WDPCP, JBTS17 and RSG1 (REM2- and RAB-like small GTPase 1), whose genes are mutated in ciliopathies. Using two contrasting evolutionary analyses, coevolution-based contact prediction and sequence conservation, we first identified the INTU/FUZ heterodimer as a novel member of homologous HerMon (Hermansky-Pudlak syndrome and MON1-CCZ1) complexes. Subsequently, we identified homologous Longin domains that are triplicated in each of these six proteins (MON1A, CCZ1, HPS1, HPS4, INTU and FUZ). HerMon complexes are known to be Rab effectors and Rab GEFs (Guanine nucleotide Exchange Factors) that regulate vesicular trafficking. Consequently, INTU/FUZ, their homologous complex, is likely to act as a GEF during activation of Rab GTPases involved in ciliogenesis.

Supplementary information

Supplementary data are available at Bioinformatics online.

FoxO1-mediated inhibition of STAT1 alleviates tubulointerstitial fibrosis and tubule apoptosis in diabetic kidney disease

Background

Tubulointerstitial fibrosis (TIF) plays an important role in the progression of diabetic kidney disease (DKD). Forkhead box O1 (FoxO1) is involved in the regulation of metabolism and cell apoptosis, but its function in renal TIF induced by DKD is less well understood.

Methods

Human kidney biopsies with DKD and normal controls were used to detect apoptosis and TIF induced by diabetes. A mouse model with kidney-specific overexpression of Pax2-3aFoxO1 was established to further investigate the functions of FoxO1 in vivo. The in vitro roles of FoxO1 were analyzed in HK-2 cells with 3aFoxO1-knockin (3aFoxO1-KI) or FoxO1-knockdown (FoxO1-KD) via CRISPR/Cas9. Western blot, immunohistochemistry, and chromatin immunoprecipitation were used to explore the underlying mechanisms.

Findings

In this study, DKD patients had increased renal TIF and apoptosis. In vivo study showed that kidney-specific overexpression of Pax2-3aFoxO1 significantly reduced the expression of p-STAT1 with resultant renal functional impairment, retarding renal TIF and apoptosis in diabetic mice. Meanwhile, We observed that FoxO1-KD in HK-2 cells aggravated the expression of p-STAT1, leading to activation of epithelial-to-mesenchymal transition (EMT) and intrinsic apoptotic pathway. Conversely, EMT and apoptosis were significantly attenuated in HK-2 cells with 3aFoxO1-KI under hyperglycemic conditions.

Interpretation

Taken together, these data suggest that the protection role of FoxO1 against renal TIF and apoptosis in DKD is likely in part to target STAT1 signaling, which may be a promising strategy for long-term treatment of DKD.

Fund

This work was supported by grants from the National Natural Science Foundation of China (grant numbers: 81570746 and 81770812).

Stress granules are formed in renal proximal tubular cells during metabolic stress and ischemic injury for cell survival

Stress granules (SGs) are a type of cytoplasmic structures formed in eukaryotic cells upon cell stress, which mainly contain RNA-binding proteins and RNAs. The formation of SGs is generally regarded as a mechanism for cells to survive a harsh insult. However, little is known about SG formation and function in kidneys. To address this, we applied different kinds of stressors to cultured proximal tubular cells as well as a short period of ischemia-reperfusion to mouse kidneys. It was found that glycolytic inhibitors such as 2-deoxy-d-glucose and 3-(3-pyridinyl)-1-(4-pyridinyl)-2-propen-1-one induced SG formation within 30 min in these cells. Similarly, SGs were induced by inhibitors of mitochondrial respiration such as sodium azide and CCCP. Renal ischemia-reperfusion induced SG formation in the cells of proximal tubules. To test the role of SGs, we stably knocked down G3bp1, a SG core protein, in renal tubular cells by shRNA viral transduction. As expected, knockdown of G3bp1 largely disrupted the assembly of SGs. After azide or cisplatin treatment, more dead cells were found in knockdown cells compared with controls, accompanied by increases in cleaved/active caspase-3. Reintroduction of exogenous G3bp1 into knockdown cells could rescue the cell death phenotype. Taken together, our data provide the first evidence of SG formation in renal tubular cells during metabolic stress and acute kidney injury. SGs are formed to protect proximal tubular cells under these conditions. Modulation of SG biogenesis may provide a novel approach to lessen the severity of renal diseases.