Cell Death and Differentiation最新文献

Growing evidence indicates that brain-derived neurotrophic factor (BDNF) is produced in contracting skeletal muscles and is secreted as a myokine that plays an important role in muscle metabolism. However, the involvement of muscle-generated BDNF and the regulation of its vesicular trafficking, localization, proteolytic processing, and spatially restricted release during the development of vertebrate neuromuscular junctions (NMJs) remain largely unknown. In this study, we first reported that BDNF is spatially associated with the actin-rich core domain of podosome-like structures (PLSs) at topologically complex acetylcholine receptor (AChR) clusters in cultured Xenopus muscle cells. The release of spatially localized BDNF is tightly controlled by activity-regulated mechanisms in a calcium-dependent manner. Live-cell time-lapse imaging further showed that BDNF-containing vesicles are transported to and captured at PLSs in both aneural and synaptic AChR clusters for spatially restricted release. Functionally, BDNF knockdown or furin-mediated endoproteolytic activity inhibition significantly suppresses aneural AChR cluster formation, which in turn affects synaptic AChR clustering induced by nerve innervation or agrin-coated beads. Lastly, skeletal muscle-specific BDNF knockout (MBKO) mice exhibit structural defects in the formation of aneural AChR clusters and their subsequent recruitment to nerve-induced synaptic AChR clusters during the initial stages of NMJ development in vivo. Together, this study demonstrated the regulatory roles of PLSs in the intracellular trafficking, spatial localization, and activity-dependent release of BDNF in muscle cells and revealed the involvement of muscle-generated BDNF and its proteolytic conversion in regulating the initial formation of aneural and synaptic AChR clusters during early NMJ development in vitro and in vivo.

Lactates accumulation following traumatic brain injury (TBI) is detrimental. However, whether lactylation is triggered and involved in the deterioration of TBI remains unknown. Here, we first report that Tufm lactylation pathway induces neuronal apoptosis in TBI. Lactylation is found significantly increased in brain tissues from patients with TBI and mice with controlled cortical impact (CCI), and in neuronal injury cell models. Tufm, a key factor in mitophagy, is screened and identified to be mostly lactylated. Tufm is detected to be lactylated at K286 and the lactylation inhibits the interaction of Tufm and Tomm40 on mitochondria. The mitochondrial distribution of Tufm is then inhibited. Consequently, Tufm-mediated mitophagy is suppressed while mitochondria-induced neuronal apoptosis is increased. In contrast, the knockin of a lactylation-deficient Tufm^K286R mutant in mice rescues the mitochondrial distribution of Tufm and Tufm-mediated mitophagy, and improves functional outcome after CCI. Likewise, mild hypothermia, as a critical therapeutic method in neuroprotection, helps in downregulating Tufm lactylation, increasing Tufm-mediated mitophagy, mitigating neuronal apoptosis, and eventually ameliorating the outcome of TBI. A novel molecular mechanism in neuronal apoptosis, TBI-initiated Tufm lactylation suppressing mitophagy, is thus revealed.

Extrahepatic cholangiocarcinoma (ECC), a highly malignant type of cancer with increasing incidence, has a poor prognosis due to limited treatment options. Based on genomic analysis of ECC patient samples, here we report that aldo-keto reductase family 1 member C1 (AKR1C1) is highly expressed in human ECC tissues and closely associated with ECC progression and poor prognosis. Intriguingly, we show that inducible AKR1C1 knockdown triggers ECC cells to undergo ferroptosis. Mechanistically, AKR1C1 degrades the protein stability of the cytochrome P450 family member CYP1B1, a newly discovered mediator of ferroptosis, via ubiquitin-proteasomal degradation. Additionally, AKR1C1 decreases CYP1B1 mRNA level through the transcriptional factor aryl-hydrocarbon receptor (AHR). Furthermore, the AKR1C1-CYP1B1 axis modulates ferroptosis in ECC cells via the cAMP-PKA signaling pathway. Finally, in a xenograft mouse model of ECC, AKR1C1 depletion sensitizes cancer cells to ferroptosis and synergizes with ferroptosis inducers to suppress tumor growth. Therefore, the AKR1C1-CYP1B1-cAMP signaling axis is a promising therapeutic target for ECC treatment, especially in combination with ferroptosis inducers.

Oxaliplatin-based therapeutics is a widely used treatment approach for hepatocellular carcinoma (HCC) patients; however, drug resistance poses a significant clinical challenge. Epigenetic modifications have been implicated in the development of drug resistance. In our study, employing siRNA library screening, we identified that silencing the m⁶A writer METTL3 significantly enhanced the sensitivity to oxaliplatin in both in vivo and in vitro HCC models. Further investigations through combined RNA-seq and non-targeted metabolomics analysis revealed that silencing METTL3 impeded the pentose phosphate pathway (PPP), leading to a reduction in NADPH and nucleotide precursors. This disruption induced DNA damage, decreased DNA synthesis, and ultimately resulted in cell cycle arrest. Mechanistically, METTL3 was found to modify E3 ligase TRIM21 near the 3’UTR with N⁶-methyladenosine, leading to reduced RNA stability upon recognition by YTHDF2. TRIM21, in turn, facilitated the degradation of the rate-limiting enzyme of PPP, G6PD, through the ubiquitination-proteasome pathway. Importantly, high expression of METTL3 was significantly associated with adverse prognosis and oxaliplatin resistance in HCC patients. Notably, treatment with the specific METTL3 inhibitor, STM2457, significantly improved the efficacy of oxaliplatin. These findings underscore the critical role of the METTL3/TRIM21/G6PD axis in driving oxaliplatin resistance and present a promising strategy to overcome chemoresistance in HCC.

Apoptosis is a fundamental process of all mammalian cells but exactly how it is regulated in different primary cells remains less explored. In most contexts, apoptosis is engaged to eliminate cells. However, postmitotic cells such as neurons must efficiently balance the need for developmental apoptosis versus the physiological needs for their long-term survival. Neurons are capable of reversing the commitment to death even after the point of cytochrome c release. This ability of neurons to recover from an apoptotic signal suggests that activation of the apoptotic pathway in neurons could be much more transient than is currently recognized. Here, we investigated whether the apoptotic pathway in neurons is a persistent signal or a transient pulse in continuous presence of apoptotic stimulus. We have examined this at three key steps in apoptotic signaling: phosphorylation of c-Jun, induction of the BH3-only family proteins and Bax activation. Strikingly, we found all three of these events occur as transient signals following Nerve Growth Factor (NGF) deprivation-induced apoptosis in sympathetic neurons. This transient apoptosis signal would effectively allow neurons to reset and permit recovery if the apoptotic stimulus is reversed. Excitingly, we have also discovered that a neuron’s ability to recover from an apoptotic signal is dependent on expression of the anti-apoptotic Bcl-2 family protein Bcl-xL. Bcl-xL-deficient neurons lose the ability to recover from NGF deprivation even if NGF is restored. Additionally, we show that recovery from a previous exposure to NGF deprivation is protective against subsequent deprivation. Together, these results define a novel mechanism by which apoptosis is regulated in neurons where the transient pulse of the apoptotic signaling supports neuronal resilience.

Receptor-interacting protein 1 (RIP1, RIPK1) is a critical mediator of multiple signaling pathways that promote inflammatory responses and cell death. The kinase activity of RIP1 contributes to the pathogenesis of a number of inflammatory and neurodegenerative diseases. However, the role of RIP1 in retinopathies remains unclear. This study demonstrates that RIP1 inhibition protects retinal ganglion cells (RGCs) in preclinical glaucoma models. Genetic inactivation of RIP1 improves RGC survival and preserves retinal function in the preclinical glaucoma models of optic nerve crush (ONC) and ischemia–reperfusion injury (IRI). In addition, the involvement of necroptosis in ONC and IRI glaucoma models was examined by utilizing RIP1 kinase-dead (RIP1-KD), RIP3 knockout (RIP3-KO), and MLKL knockout (MLKL-KO) mice. The number of RGCs, retinal thickness, and visual acuity were rescued in RIP1-kinase-dead (RIP1-KD) mice in both models, while wild-type (WT) mice experienced significant retinal thinning, RGC loss, and vision impairment. RIP3-KO and MLKL-KO mice showed moderate protective effects in the IRI model and limited in the ONC model. Furthermore, we confirmed that a glaucoma causative mutation in optineurin, OPTN-E50K, sensitizes cells to RIP1-mediated inflammatory cell death. RIP1 inhibition reduces RGC death and axonal degeneration following IRI in mice expressing OPTN-WT and OPTN-E50K variant mice. We demonstrate that RIP1 inactivation suppressed microglial infiltration in the RGC layer following glaucomatous damage. Finally, this study highlights that human glaucomatous retinas exhibit elevated levels of TNF and RIP3 mRNA and microglia infiltration, thus demonstrating the role of neuroinflammation in glaucoma pathogenesis. Altogether, these data indicate that RIP1 plays an important role in modulating neuroinflammation and that inhibiting RIP1 activity may provide a neuroprotective therapy for glaucoma.

The transcription factor p53 plays a key role in the cellular defense against cancer development. It is inactivated in virtually every tumor, and in every second tumor this inactivation is due to a mutation in the TP53 gene. In this perspective, we show that this diverse mutational spectrum is unique among all other cancer-associated proteins and discuss what drives the selection of TP53 mutations in cancer. We highlight that several factors conspire to make the p53 protein particularly vulnerable to inactivation by the mutations that constantly plague our genome. It appears that the TP53 gene has emerged as a victim of its own evolutionary past that shaped its structure and function towards a pluripotent tumor suppressor, but came with an increased structural fragility of its DNA-binding domain. TP53 loss of function - with associated dominant-negative effects - is the main mechanism that will impair TP53 tumor suppressive function, regardless of whether a neomorphic phenotype is associated with some of these variants.

By the time a tumor reaches clinical detectability, it contains around 10⁸–10⁹ cells. However, during tumor formation, significant cell loss occurs due to cell death. In some estimates, it could take up to a thousand cell generations, over a ~ 20-year life-span of a tumor, to reach clinical detectability, which would correspond to a “theoretical” generation of ~10³⁰ cells. These rough calculations indicate that cancers are under negative selection. The fact that they thrive implies that they “evolve”, and that their evolutionary trajectories are shaped by the pressure of the environment. Evolvability of a cancer is a function of its heterogeneity, which could be at the genetic, epigenetic, and ecological/microenvironmental levels [1]. These principles were summarized in a proposed classification in which Evo (evolutionary) and Eco (ecological) indexes are used to label cancers [1]. The Evo index addresses cancer cell-autonomous heterogeneity (genetic/epigenetic). The Eco index describes the ecological landscape (non-cell-autonomous) in terms of hazards to cancer survival and resources available. The reciprocal influence of Evo and Eco components is critical, as it can trigger self-sustaining loops that shape cancer evolvability [2]. Among the various hallmarks of cancer [3], metabolic alterations appear unique in that they intersect with both Evo and Eco components. This is partly because altered metabolism leads to the accumulation of oncometabolites. These oncometabolites have traditionally been viewed as mediators of non-cell-autonomous alterations in the cancer microenvironment. However, they are now increasingly recognized as inducers of genetic and epigenetic modifications. Thus, oncometabolites are uniquely positioned at the crossroads of genetic, epigenetic and ecological alterations in cancer. In this review, the mechanisms of action of oncometabolites will be summarized, together with their roles in the Evo and Eco phenotypic components of cancer evolvability. An evolutionary perspective of the impact of oncometabolites on the natural history of cancer will be presented.