Cell Death and Differentiation最新文献

Dysfunctional adipogenesis is a major contributor of obesity. N-acetyltransferase 10 (NAT10) plays a crucial role in regulating N4-acetylcysteine (ac4C) modification in tRNA, 18SrRNA, and mRNA. As the sole “writer” in the ac4C modification process, NAT10 enhances mRNA stability and translation efficiency. There are few reports on the relationship between NAT10 and adipogenesis, as well as obesity. Our study revealed a significant upregulation of NAT10 in adipose tissues of obese individuals and high-fat diet-fed mice. Furthermore, our findings revealed that the overexpression of NAT10 promotes adipogenesis, while its silencing inhibits adipogenesis in both human adipose tissue-derived stem cells (hADSCs) and 3T3-L1 cells. These results indicate the intimate relationship between NAT10 and obesity. After silencing mouse NAT10 (mNAT10), we identified 30 genes that exhibited both hypo-ac4C modification and downregulation in their expression, utilizing a combined approach of acRIP-sequencing (acRIP-seq) and RNA-sequencing (RNA-seq). Among these genes, we validated KLF9 as a target of NAT10 through acRIP-PCR. KLF9, a pivotal transcription factor that positively regulates adipogenesis. Our findings showed that NAT10 enhances the stability of KLF9 mRNA and further activates the CEBPA/B-PPARG pathway. Furthermore, a dual-luciferase reporter assay demonstrated that NAT10 can bind to three motifs of mouse KLF9 and one motif of human KLF9. In vivo studies revealed that adipose tissue-targeted mouse AAV-NAT10 (AAV-shRNA-mNAT10) inhibits adipose tissue expansion in mice. Additionally, Remodelin, a specific NAT10 inhibitor, significantly reduced body weight, adipocyte size, and adipose tissue expansion in high-fat diet-fed mice by inhibiting KLF9 mRNA ac4C modification. These findings provide novel insights and experimental evidence of the prevention and treatment of obesity, highlighting NAT10 and its downstream targets as potential therapeutic targets.

Mammalian mitochondria undergo Ca²⁺-induced and cyclosporinA (CsA)-regulated permeability transition (mPT) by activating the mitochondrial permeability transition pore (mPTP) situated in mitochondrial inner membranes. Ca²⁺-induced prolonged openings of mPTP under certain pathological conditions result in mitochondrial swelling and rupture of the outer membrane, leading to mitochondrial dysfunction and cell death. While the exact molecular composition and structure of mPTP remain unknown, mammalian ATP synthase was reported to form voltage and Ca²⁺-activated leak channels involved in mPT. Unlike in mammals, mitochondria of the crustacean Artemia franciscana have the ability to accumulate large amounts of Ca²⁺ without undergoing the mPT. Here, we performed structural and functional analysis of A. franciscana ATP synthase to study the molecular mechanism of mPTP inhibition in this organism. We found that the channel formed by the A. franciscana ATP synthase dwells predominantly in its inactive state and is insensitive to Ca²⁺, in contrast to porcine heart ATP synthase. Single-particle cryo-electron microscopy (cryo-EM) analysis revealed distinct structural features in A. franciscana ATP synthase compared with mammals. The stronger density of the e-subunit C-terminal region and its enhanced interaction with the c-ring were found in A. franciscana ATP synthase. These data suggest an inactivation mechanism of the ATP synthase leak channel and its possible contribution to the lack of mPT in this organism.

The plasma concentrations of acyl CoA binding protein (ACBP) encoded by the gene diazepam binding inhibitor (DBI) are increased in patients with severe osteoarthritis (OA). Here, we show that knee OA induces a surge in plasma ACBP/DBI in mice subjected to surgical destabilization of one hind limb. Knockout of the Dbi gene or intraperitoneal (i.p.) injection of a monoclonal antibody (mAb) neutralizing ACBP/DBI attenuates OA progression in this model, supporting a pathogenic role for ACBP/DBI in OA. Furthermore, anti-ACBP/DBI mAb was also effective against OA after its intraarticular (i.a.) injection, as monitored by sonography, revealing the capacity of ACBP/DBI to locally reduce knee inflammation over time. In addition, i.a. anti-ACBP/DBI mAb improved functional outcomes, as indicated by the reduced weight imbalance caused by OA. At the anatomopathological level, i.a. anti-ACBP/DBI mAb mitigated histological signs of joint destruction and synovial inflammation. Of note, i.a. anti-ACBP/DBI mAb blunted the OA-induced surge of plasma ACBP/DBI, as well as that of other inflammatory factors including interleukin-1α, interleukin-33, and tumor necrosis factor. These findings are potentially translatable to OA patients because joints from OA patients express both ACBP/DBI and its receptor GABA_ARγ2. Moreover, a novel mAb against ACBP/DBI recognizing an epitope conserved between human and mouse ACBP/DBI demonstrated similar efficacy in mitigating OA as an anti-mouse ACBP/DBI-only mAb. In conclusion, ACBP/DBI might constitute a promising therapeutic target for the treatment of OA.

Impaired glucose uptake regulated by suppressed insulin receptor signaling is a key driving force of podocytopathies. The identification of potential therapeutic targets that mediate podocyte insulin receptor signaling holds significant clinical importance. Here, we observed a substantial reduction in PR domain-containing 16 (PRDM16) expression within damaged podocytes in both humans and mice. Podocyte-specific Prdm16 deletion aggravated podocyte injury, albuminuria, and glomerulosclerosis in diabetic nephropathy (DN) mice. Conversely, exogenous PRDM16 delivered by lentivirus mitigated these pathological changes in DN mice and adriamycin (ADR) nephropathy mice. Furthermore, we demonstrated that loss of PRDM16 blocked glucose uptake of podocytes by inhibiting insulin receptor signaling. Mechanistically, PRDM16 deficiency downregulated the transcription of NEDD4L, subsequently enhancing the stability of IKKβ protein. The accumulation of IKKβ caused by the loss of PRDM16 led to the phosphorylation of serine residues on insulin receptor substrate-1 (IRS-1), thereby promoting IRS-1 degradation. Exogenous NEDD4L mitigated podocyte injury induced by PRDM16 knockdown in vitro and attenuated ADR nephropathy in vivo. Our study clarified the role and mechanism of PRDM16 in insulin receptor signaling and podocyte injury, providing a potential therapeutic target for podocytopathies.

Efferocytosis is crucial for the clearance of apoptotic cells (ACs) following acute ischemic stroke (AIS), however, its mechanism remains unclear. This study reveals that chemokine-like factor 1 (CKLF1) disrupts efferocytosis by promoting AC finding and internalization while impairing AC degradation in microglia. CKLF1 deficiency reduced the proportion of ACs and lowered levels of damage-associated molecular patterns. Mechanistically, CKLF1 binds to phosphatidylserine on apoptotic neurons/blebs, recruiting microglia to the ischemic penumbra via a C-C chemokine receptor 4 (CCR4)-dependent pathway. Apoptotic blebs with CKLF1 are engulfed into microglia, triggering the rapid production of interleukin-6 (IL6). IL6 enhances AC internalization through the signal transducer and activator of transcription 3 (STAT3)-vav guanine nucleotide exchange factor 1 (VAV1)-ras-related C3 botulinum toxin substrate 1 (RAC1) signaling cascade but simultaneously inhibits transcription factor EB (TFEB) nuclear translocation, leading to lysosomal dysfunction. This effect results in AC accumulation, compromising microglial efferocytosis efficiency and integrity. These findings uncover a novel regulatory axis induced by CKLF1, emphasizing the complex balance between AC internalization and degradation in microglial efferocytosis.

Pancreatic ductal adenocarcinoma is characterized by a three-dimensional (3D) tumor microenvironment devoid of oxygen and nutrients but enriched in extracellular matrix, which acts as a physical and chemical barrier. In 3D, cancer cells reprogram their metabolic pathways in ways that help them survive hostile conditions. However, little is known about the metabolic phenotypes of cancer cells in 3D and the intrinsic cues that modulate them. We found that Cxcl5 deletion restricted pancreatic tumor growth in a 3D spheroid-in-Matrigel culture system without affecting cancer cell growth in 2D culture. Cxcl5 deletion impaired 3D-specific global metabolic reprogramming, resistance to hypoxia-induced cell death, and upregulation of Hif1α and Myc. Overexpression of Hif1α and Myc, however, effectively restored 3D culture-induced metabolic reconfiguration, growth, redox homeostasis, and mitochondrial function in Cxcl5^−/− cells, reducing ferroptosis. We also found that pancreatic cancer patients with higher expression of hypoxia and metabolism-related genes whose expression is well-correlated with CXCL5 generally have poorer prognosis. Together, our findings identify an unanticipated role of Cxcl5 in orchestrating the cancer metabolic reprogramming in 3D culture that is required for energy and biomass maintenance and that restricts oxidative cell death. Thus, our results provide a rationale for targeting CXCL5 as a promising therapeutic strategy.

The colonic crypts are principally composed by Lgr5⁺ stem cells and deep crypt secretory (DCS) cells. c-Kit-expressing cells mark DCS cells and supply Wnt3, EGF, and Notch signals to support their neighboring crypt bottom-intermingled Lgr5⁺ cells. However, the role of c-Kit⁺ cells beyond supporting Lgr5⁺ cells in colonic epithelium remains unexplored. Here, we identify that c-Kit⁺ cells are a heterogeneous entity and possess stemness potency to differentiate into the entire spectrum of epithelial cells and renew the homeostatic colon. Intriguingly, c-Kit⁺ cells play a pivotal role in epithelium repair in mouse models of colitis when contemporary Lgr5⁺ cells are insufficient or absent. Depletion of c-Kit⁺ cells or inhibition of SCF/c-Kit signaling worsens, while supplementation of SCF alleviates colonic epithelium injury during colitis. Our findings unravel the fate and function of c-Kit⁺ cells in homeostatic colon and recovery during colonic epithelium injury which has translational implications for human inflammatory bowel diseases.

The ubiquitination of histone H2A/H2AX, catalyzed by RNF8/RNF168, is a crucial step in the repair of DNA double-strand breaks (DSBs), playing a significant role in transmitting and amplifying DNA damage response signals. However, the upstream regulatory mechanisms of RNF168 remain unclear. Here, we demonstrate that ZNF451 catalyzes the SUMOylation of RNF168, thereby regulating the ubiquitination of histone H2A/H2AX. Specifically, ZNF451 rapidly responds to radiation-induced DNA damage, accumulating abundantly at damage sites and catalyzing the SUMO2 modification of RNF168. This modification stabilizes RNF168, enhancing its accumulation at damage sites, which increases the ubiquitination levels of downstream histone H2A/H2AX and promotes the DNA damage repair process. Furthermore, we find that ZNF451 and RNF8 jointly regulate RNF168 in a novel manner, exhibiting both competitive and cooperative characteristics. The interaction between RNF168 and either ZNF451 or RNF8 mutually inhibits each other. However, simultaneous loss of ZNF451 and RNF8 markedly impedes the recruitment of RNF168 to damage sites. Whereas, varying expression levels of ZNF451 and RNF8 suggest that both facilitate the interaction between RNF168 and the downstream factor H2AX, but the interaction plateaus beyond a specific threshold. Altogether, these findings reveal that the SUMOylation catalyzed by ZNF451 is involved in regulating RNF168-induced ubiquitin signaling in DSBs repair and suggest that ZNF451 could serve as a potential therapeutic target in tumor radiotherapy.

Cells produce metabolic intermediates through catalytic reactions, mainly via post-translational modifications. The modification of proteins by O-linked N-acetylglucosamine, known as O-GlcNAcylation, is one of the most common post-translational modifications. As O-GlcNAcylation and phosphorylation can occur at serine or threonine residues, it is crucial that the interplay between these two modifications is vital to bioenergetic and biosynthetic demand. Although emerging recognition linking O-GlcNAc modification and phosphorylation to protein functions has been obtained, the issue of how altered O-GlcNAcylation or phosphorylation regulates each other in the metabolic system remains uncertain. The combination of cell biological and proteomic approaches over the recent few years has not only highlighted the interactions between O-GlcNAcylation and phosphorylation in protein function but also prompted us to elucidate the underlying mechanisms behind this crosstalk controlling metabolic homeostasis. The purpose of this review is to summarize recent advances in the O-GlcNAcylation/phosphorylation regulation of the metabolic process. An extensive exploration of this interplay has significant implications for metabolic control systems, including glucose, lipid, and nucleotide metabolism, where dysregulation in O-GlcNAcylation and phosphorylation of metabolic syndrome is essential.