Cell Death and Differentiation最新文献

Our previous studies demonstrated that the fat mass and obesity-associated protein (FTO) is upregulated in colorectal cancer (CRC). It demethylates G6PD/PARP1 and SLC7A11/GPX4 mRNAs, thereby protecting CRC from DNA damage and ferroptotic cell death. However, the mechanisms underlying FTO upregulation in CRC remain unclear. Unexpectedly, we show Ubiquitin-specific peptidase 30 (USP30) binds serine/glycine and senses their levels to protect FTO from proteosome degradation. Stabilized FTO demethylates 3-phosphoglycerate dehydrogenase (PHGDH) and phosphoserine aminotransferase 1 (PSAT1) mRNAs and inhibits their degradation in an m⁶A-YTHDF2-dependent manner, thereby promoting serine synthesis and CRC tumor growth. Furthermore, we identify sodium 2, 2-dichloroacetate (DCA) as a novel inhibitor of USP30, and DCA inhibits CRC serine synthesis and tumor growth. Clinically, USP30, FTO, PHGDH, and PSAT1 levels are highly correlated in CRC tissues. This study provides mechanistic insights into how USP30 senses serine/glycine levels to regulate serine synthesis via the FTO-PHGDH/PSAT1 axis, offering a potential therapeutic strategy for targeting serine/glycine metabolism in cancer.

Entosis is a non-apoptotic cell death process implicated in various important biological processes, such as tumorigenesis. Entotic death is preceded with the formation of cell-in-cell structures that are well known to be controlled by two spatially separated core elements: adherens junction and actomyosin. However, the molecular mechanism underlying their coordination remains a longstanding open question. In this study, by profiling isogenic breast cancer cells, ARHGAP36 was identified as a potent inducer of entotic cell-in-cell formation, consistent with multiple lines of tumor-suppressive evidence both in vitro and in vivo. This effect is attributed to the concomitant promotion of P-cadherin-mediated cell-cell adhesion and RhoA-regulated actomyosin contraction. Mechanistically, ARHGAP36, through the arginine-rich domain at the N-terminal, binds to β-catenin to stabilize P-cadherin expression in a way accompanying with, and mutually exclusive from, its interaction with PKAc to activate RhoA signaling. Thus, this study unveiled a heretofore unrecognized coordination mechanism for entosis, where ARHGAP36 engages both adherens junction and actomyosin to drive cell-in-cell formation, providing a promising cancer therapeutic target.

The pro-inflammatory programmed cell death pathway, necroptosis, relies on phosphorylation of the terminal effector, MLKL, by RIPK3. RIPK3-deficient mice or those harboring the kinase-inactivating mutation, RIPK3^K51A, are ostensibly normal in the absence of challenge, indicating that RIPK3 and its kinase activity are dispensable for development. However, another kinase-inactivating mutation, RIPK3^D161N, results in embryonic lethality in mice due to widespread apoptosis. As a result, the RIPK3^D161N mutation is thought to confer a toxic gain-of-function. Here, to further explore the impacts of RIPK3 inactivation, we compared the stability and cellular interactions of RIPK3^D161N and RIPK3^K51A to a third previously-uncharacterized kinase-dead variant, RIPK3^D143N. We show that RIPK3^K51A was unstable and did not associate with RIPK1, RIPK3^D161N was unstable but interacted with RIPK1, whereas RIPK3^D143N was stable and bound RIPK1 in a manner comparable to wild-type RIPK3. Thus, all three variants scaffold differently, suggesting that the assembly of cell death machinery by RIPK3 is finely tuned, not just by its kinase activity, but also by the conformation of its kinase domain. Physiologically, Ripk3^D143N/D143N mice exhibited a partially penetrant lethality in utero. However, once born, Ripk3^D143N/D143N mice were fertile and phenotypically indistinguishable from wild-type mice in the absence of challenge. Full blockade of necroptotic signaling was shown in cells from Ripk3^D143N/D143N mice, with the RIPK3^D143N mutation also protecting Casp8^-/- mice from lethal necroptosis during embryogenesis and preventing necroptotic ileitis in mice that lacked intestinal epithelial caspase-8 expression. Our studies support the idea that RIPK3 is a nexus between apoptotic and necroptotic signaling, and highlight the importance of considering kinase domain conformation in RIPK3 inhibitor development.

RNA processing generates diverse protein-coding and non-coding transcripts, yet RNA biotype diversity during cellular differentiation is not well characterized. Merkel cells (MCs) are cutaneous mechanosensors. We analyzed full-length transcripts of FACS-sorted single mouse MCs at all stages of development and discovered that their terminal differentiation was accompanied by an emergence of non-coding transcripts associated with genes related to MC function. Non-coding RNAs upregulated during terminal differentiation included retained intron transcripts capable of forming nuclear condensates that contained their cognate mRNAs. We showed that Aspa retained intron condensates prevented the nuclear export of Aspa mRNA, reducing ASPA expression. Transcripts associated with terminal differentiation in five other mammalian cell types also showed an increased abundance of non-coding biotypes and this was attenuated in differentiation-defective Down syndrome neurons. These findings strongly suggest that the emergence of non-coding transcripts is a general feature of terminal differentiation and retained intron condensates can function to regulate gene expression.

SMAC is a mitochondrial intermembrane space protein, which is released during apoptosis and whose known function is antagonism of inhibitor of apoptosis proteins in the cytosol, to facilitate caspase activation. Recent data suggest that SMAC can also be released by sub-lethal signals in the apoptosis pathway, in the absence of cell death. We here explored potential functions of SMAC in non-apoptotic cells. We found that a portion of SMAC is spontaneously released into the cytosol in the absence of apoptosis, regulated by the BCL-2-family proteins BAX and BAK and the fission GTPase DRP1. In cancer cell lines, SMAC was required for the activation of caspases in lethal and non-lethal conditions, while this contribution to caspase-activation was much smaller in non-malignant fibroblast lines. In cells with high levels of cytosolic SMAC, SMAC deficiency reduced in vitro migration, invasion and anchorage-independent growth as well as metastasis in a xenograft model in zebrafish. SMAC-deficient cells further showed a reduced activity in interferon signaling, associated with reduced cytosolic presence of mitochondrial DNA and activation of the stimulator of interferon genes (STING), and SMAC expression levels correlated with interferon-induced genes in cancer data sets. We further found that SMAC can regulate mitochondrial morphology and integrity. Finally, high gene-expression of SMAC was associated with poor prognosis in patients of several cancer types. These results identify SMAC as a regulator of inflammation and growth behavior of cancer cells. They further report a mitochondrial function of SMAC and demonstrate a role of SMAC in human cancer biology across several cancer entities.

eIF6 is overexpressed in multiple cancers. Previous work has showed that deficiency alters the gut microbiota. This study investigated the mechanism linking eIF6 deficiency, microbial dysbiosis, and colorectal cancer (CRC). eIF6 expression was assessed in human and mouse CRC samples. Functional assays were conducted in mice with AOM/DSS-induced CRC. Antibiotic treatment and faecal microbiota transplantation (FMT) were applied to evaluate microbiota-mediated effects. 16S rDNA sequencing and Dubosiella newyorkensis (D. newyorkensis) supplementation were used to identify key bacteria. Metabolites from the bacterial supernatant were analysed via targeted mass spectrometry. The effect of indole-3-carboxaldehyde (3-ICA) was tested in murine models. eIF6 expression was upregulated in CRC. Its deficiency reduced the tumour incidence and proliferation of tumours in mice and increased the abundance of beneficial bacteria such as Akkermansia and Dubosiella. FMT from eIF6 deficient mice and D. newyorkensis administration attenuated tumorigenesis and enhanced barrier function. 3-ICA, a metabolite of D. newyorkensis, also suppressed CRC progression. eIF6 deficiency exerts protective effects against CRC through the enrichment of D. newyorkensis and its metabolite 3-ICA, revealing a novel mechanism and potential therapeutic strategy for CRC.

BOK is a pro-apoptotic member of the BCL-2 family frequently repressed in cancer and with emerging roles beyond apoptosis. BOK interacts with and increases uridine monophosphate synthetase (UMPS) activity, thereby promoting uridine monophosphate (UMP) synthesis. We previously showed that BOK protein is downregulated in primary human lung cancer samples, correlating with poorer patient survival. Here, we demonstrate that BOK deficiency increases DNA damage, triggering p53 activation and cell cycle arrest in two independent non-small cell lung cancer (NSCLC) cell models that express either WT or defective p53. In a p53-deficient setting, BOK loss caused elevated baseline DNA damage rendering cells more dependent on alternative DNA repair pathways. We exploited this vulnerability by inhibiting the ATR-mediated DNA damage response pathway with the selective ATR inhibitor ceralasertib (AZD6738). ATR inhibition in BOK/p53 compound-deficient NSCLC cells exacerbated DNA damage and induced cell death, indicating a synthetic lethal interaction. The DNA damage in BOK-deficient cells was rescued by a cell permeable BOK-BH3-derived peptide, confirming the mechanistic link between BOK and UMPS. Taken together, our findings reveal a vulnerability in NSCLC, where combined loss of p53 and BOK sensitises cells to ATR inhibition. This synthetic interaction suggests that p53-deficient tumours with reduced BOK expression may be more reliant on ATR-mediated DNA repair, providing a mechanistic basis for their susceptibility to ATR inhibitors. Given the frequent inactivation of p53 in lung cancer, our study offers a rationale for clinical exploration of ATR inhibitors, in combination with standard chemotherapy, in the context of reduced BOK function. Future investigations into the broader role of BOK in genomic stability and nucleotide metabolism may uncover additional therapeutic strategies for cancers with repressed BOK.