Cell Discovery最新文献

HOIP, an RBR-type E3 ligase and the catalytic subunit of the linear ubiquitin chain assembly complex (LUBAC), plays crucial roles in various cellular processes, including the NF-κB signaling pathway. The E3 activity of HOIP can be inhibited by the kinase STK4-mediated phosphorylation, although the mechanism is poorly understood. In this study, using biochemical, mass spectrometry and structural approaches, we systemically characterize the association of STK4 with HOIP, and unveil that STK4 can directly bind to the RING2-LDD module of HOIP through its kinase domain. The determined crystal structure of STK4 in complex with HOIP RING2-LDD not only elucidates the detailed binding mechanism of STK4 with HOIP, but also uncovers, for the first time, a unique binding mode of STK4 with its substrate. Moreover, we reveal that STK4 can directly phosphorylate the T786 residue of HOIP that is located in the allosteric ubiquitin-binding site of HOIP. Importantly, the phosphorylation of HOIP T786 mediated by STK4 can block the binding of ubiquitin to the allosteric site of HOIP, thereby attenuating the E3 activity of HOIP. In all, our findings provide mechanistic insights into the interaction between STK4 and HOIP as well as the negative regulation of HOIP's E3 activity by STK4-mediated phosphorylation, which are valuable for further understanding the regulatory modes of RBR-type E3 ligases.

Adverse intrauterine environments, such as hyperglycemia, impair sexual reproduction and species continuity, yet the underlying mechanisms remain poorly understood. In this study, we demonstrated that intrauterine hyperglycemia significantly disrupted primordial germ cell (PGC) development, especially in female offspring, thus reducing fertility. Using Oct4-EGFP transgenic mice with intrauterine hyperglycemia exposure, we revealed that hyperglycemia compromised sexually specific chromatin accessibility and DNA methylation reprogramming during PGC development. Particularly, in female PGCs, hyperglycemia leads to the aberrant retention of chromatin accessibility at pluripotency gene promoters such as Nanog and Tfap2c, inhibiting proper gene silencing and blocking the initiation of meiosis, which ultimately hinders oocyte maturation. Conversely, male PGCs exhibit less severe changes in chromatin accessibility and gene transcription. Intriguingly, the global DNA methylation reconstruction is impaired in male PGCs, particularly in key imprinted gene regions, suggesting potential developmental ramifications for later stages and even subsequent generations. Particularly, our findings indicate that intrauterine hyperglycemia adversely affects sex differentiation in PGCs by disrupting the expression of critical sex-determining transcription factors. Collectively, these findings highlight how intrauterine hyperglycemia interferes with sex-specific epigenetic reprogramming during PGC development, leading to abnormal germ cell development, reduced fertility, and adverse intergenerational effects.

In the evolutionary arms race between bacteria and viruses, retrons have emerged as distinctive antiphage defense systems. Here, we elucidate the structure and function of Retron-Eco2, which comprises a non-coding RNA (ncRNA) that encodes multicopy single-stranded DNA (msDNA, a DNA‒RNA hybrid) and a fusion protein containing a reverse transcriptase (RT) domain and a topoisomerase-primase-like (Toprim) effector domain. The Eco2 msDNA and RT-Toprim fusion protein form a 1:1 stoichiometric nucleoprotein complex that further assembles into a trimer (msDNA:RT-Toprim ratio of 3:3) with a distinctive triangular configuration. The RNA portion of the msDNA in one protomer closely intertwines around the RT domain of an adjacent protomer, mediating the formation of this self-inhibitory assembly. Upon activation, the Toprim effector domain exhibits RNase activity, degrading RNA to arrest phage replication. We further reveal that phage mutants evading Eco2-mediated defense harbor mutations in the endonuclease IV-like protein DenB, underscoring DenB's critical role in triggering the activation of this system. Together, these findings provide key structural and functional insights into Retron-Eco2, laying the groundwork for harnessing its potential in biotechnology and synthetic biology applications.

Brain parenchymal metastases (BM) and leptomeningeal metastases (LM) represent distinct subtypes of central nervous system metastases (CNSm) from lung cancer, posing significant clinical challenges. The local immune landscape of LM remains elusive. Herein, we utilized single-cell RNA sequencing to build a cell atlas of LM, and systematically examine the immune profiling and cell heterogeneity between BM and LM. Our analysis reveals that BM has more CXCL9⁺ macrophages, CXCL13⁺CD4⁺ T cells and B cells than LM, exhibiting the presence of tertiary lymphoid (TLS) structures, which is associated with a favorable response to tyrosine kinase inhibitors (TKI). Conversely, a remarkably immunosuppressive tumor microenvironment (TME) is detected in LM, characterized by lymphocyte depletion and a concurrent enrichment of SPP1⁺ macrophages, compared to BM. Furthermore, we identified significant blood-brain barrier (BBB) cell discrepancies between BM and LM, and substantial phenotypic reprogramming of BBB cells in CNSm. This reprogramming encompassed alterations in transporter gene expression, extracellular matrix production and dysregulated cell-cell interactions, potentially contributing to the metastatic process. In summary, this study highlights the divergent cellular and molecular landscapes of BM vs LM, offering critical insights into potential therapeutic targets and informing the development of improved treatment strategies for non-small cell lung cancer patients with CSNm.

Disuse-induced bone loss occurs in long-term bed-ridden patients and in astronauts during spaceflight. The underlying mechanisms are poorly understood. In a rodent model of disuse-induced bone loss (called hindlimb unloading (HU)), we observed that decreased numbers of leptin receptor (LepR) positive mesenchymal stem cells (MSCs) in adult bone marrow, contribute to bone loss. MicroRNA-337-3p (miR-337) was upregulated in MSCs upon HU and inhibited MSC proliferation by directly targeting IRS-1 to suppress the PI3kinase-Akt-mTOR pathway. Piezo1 was the upstream receptor for sensing mechanical stress and regulated miR-337 through the Hippo-YAP signaling pathway. Remarkably, the knockout of miR-337 significantly attenuated HU-induced, but not ovariectomy-induced, bone loss by increasing MSC proliferation and osteogenesis. Finally, the transplantation of miR-337^-/- MSCs into wild-type HU mice was sufficient to mitigate bone loss. These findings reveal the cellular and molecular mechanisms underlying disuse-induced bone loss and highlight a feasible therapeutic strategy to prevent disuse- or microgravity-induced bone loss on Earth and during spaceflight.

A hallmark of aging is chronic systemic inflammation, which is exacerbated by the hypersecretory aging phenotype known as the senescence-associated secretory phenotype (SASP). How the SASP is initiated to accelerate tissue inflammation and aging is an outstanding question in aging biology. Here, we showed that phosphorylation of the Mediator subunit MED15 at T603 is able to control the SASP and aging. Transforming growth factor-β selectively induces CDK1-mediated MED15 T603 phosphorylation to control SASP gene expression. The MED15 T603 dephosphorylated mutant (T603A) inhibits the SASP and cell senescence, whereas the T603 phosphorylation-mimicking mutant (T603D) has the opposite effect. Mechanistically, forkhead box protein A1 preferentially binds to unphosphorylated but not phosphorylated MED15 at T603 to suppress SASP gene expression. Notably, aging mice harboring dephosphorylated mutation in this phosphosite exhibit improved learning and memory through the attenuation of the SASP across tissues. Overall, our study indicates that MED15 T603 phosphorylation serves as a control switch for SASP production, which underlies tissue aging and cognitive decline and provides a novel target for age-related pathogenesis.

The liver is a major target organ for breast cancer metastasis, while the regulatory mechanism of liver colonization by breast cancer remains largely unclear. Neutrophils are known to play important roles in metastatic colonization of cancer cells by the formation of neutrophil extracellular traps (NETs). Here we show the role and mechanism of a subpopulation of Kupffer cells (KCs), the liver resident macrophages, in mediating tumoral induction of NETs and liver metastasis. NETs are activated more abundantly in liver metastases of breast cancer, as compared to metastases to other organs and primary tumors. Liver-tropic tumor cells induce CD62L-expressing KCs by a secretory protein DMBT1, and CD62L⁺ KCs activate neutrophils for NETosis via the chemokine CCL8. Inhibition of CCL8 or its receptor on neutrophils, CCR1, impairs NETosis and metastasis. In addition, we identified a KC membrane protein MUC1 that binds to DMBT1 and subsequently activates NF-κB signaling in KCs, leading to CCL8 and CD62L expression. KCs with MUC1 inhibition effectively suppress liver metastasis. Furthermore, a DMBT1 neutralizing antibody was developed with the promise to inhibit tumor-KC interaction and treat metastatic cancer. In conclusion, our work reveals a KC subset that accounts for the liver tropism of breast cancer cells and NETs, and provides potential strategies in metastasis treatment.

Cancer cells can be induced to dormancy initially by specific cancer therapies, but can be reactivated for subsequent relapse as therapy-resistant cancer cells. Although the treatment-induced dormancy-to-reactivation switch is an important process in tumour spread and recurrence, little is known about the underlying molecular mechanisms, particularly the metabolic underpinnings. In this study, we demonstrated that the tryptophan catabolism-related tryptophan 2,3-dioxygenase (TDO2) -kynurenine (Kyn) -aryl hydrocarbon receptor (AhR) signalling axis was responsible for both sustaining the survival of dormant prostate cancer cells induced by androgen deprivation therapy (ADT) and promoting the reactivation of dormant cells and their recurrent outgrowth, which facilitated the development of therapeutic resistance by allowing the dormancy-to-reactivation switch. Mechanistically, we found that ADT upregulated the expression of TDO2 to produce Kyn, which activated AhR and maintained the survival of ADT-induced dormant cells. Interestingly, the switch of transcription factors from the androgen receptor (AR) to the glucocorticoid receptor (GR) modulated the persistent expression of TDO2 and promoted the reactivation of dormant cells through the same TDO2-Kyn-AhR signalling axis. Additionally, tumour recurrence following ADT was delayed by pharmacological suppression of TDO2-Kyn-AhR signalling with a TDO2 inhibitor or an AhR inhibitor. In summary, we describe a signalling circuit mediated by tryptophan metabolism for regulating tumour cell dormancy and recurrence and propose TDO2 as a new target for the treatment of androgen-sensitive prostate cancer patients in combination with ADT.