Molecular Biology of the Cell最新文献

The elevated occurrence and fatality rates of colorectal cancer (CRC) can be attributed not only to the biological attributes of uncontrolled tumor cell proliferation but also to the intricate interplay between tumor cells and surrounding cells in the microenvironment. Among these, Cancer-Associated Fibroblasts (CAFs) stand out as a predominant type of mesenchymal cell in the microenvironment, with their biological functions in tumor advancement becoming increasingly recognized. CAFs play a significant role in the progression of CRC through diverse mechanisms, such as direct interactions with tumor cells and the secretion of cytokines that modulate the recruitment and function of macrophages and immune cells. This review explored various facets of the involvement of CAFs in the progression of CRC, including their origins, subtypes, marker molecules, interactions with other cells, and the potential clinical significance of targeting CAFs or CAFs-derived molecules in the context of CRC therapy.

The small hypercondensed sperm nucleus undergoes a dramatic transformation into a large round pronucleus with relaxed chromatin during the brief cleavage period in metazoan embryos, enabling the activation of chromatin functions necessary for subsequent development. However, it remains unclear whether the egg cytoplasm-specific physicochemical properties play a role in pronucleus assembly. Here, we evaluated the impact of abundant RNAs in eggs on pronucleus assembly in Xenopus laevis cell-free reconstitution system. We found that the introduction of RNAs at an appropriate concentration led to a rapid nuclear growth, more dispersed chromatin distribution, and dissociation of sperm-specific nuclear proteins from the chromatin. These chromatin remodeling properties, which were reproducible through introduction of negatively charged compounds, facilitated the incorporation of somatic histones into chromatin in the reconstituted nuclei. Based on these findings, we propose that the remodeled chromatin by negatively charges of cytoplasmic RNAs accelerates rapid decondensation of negatively charged chromatin and pronucleus assembly during the brief cleavage period following fertilization.

Rhabdomyosarcoma is the most common pediatric soft tissue cancer, thought to arise from primitive mesenchymal cells that differentiate into skeletal muscle. Previous studies suggest that primary cilia may play a role in the development of rhabdomyosarcoma. Primary cilia are cellular structures that arise from the centrosome and serve important functions in sensory signaling, cell migration, and developmental processes. However, most rhabdomyosarcoma cell lines do not have primary cilia. Because primary cilia are derived from centrosomes, the development of rhabdomyosarcoma may, in fact, be due to the function of centrosome proteins rather than the primary cilia itself. Therefore, this study sought to determine if the centrosomal protein centriolin/Cep110, which is localized to both centrosomes and primary cilia, plays a role in rhabdomyosarcoma biology. The gene editing tool CRISPR/Cas9 was used to disrupt the centriolin/Cep110 gene in the rhabdomyosarcoma cell line CCL-136, and the effects on cell viability and cell cycle progression were assayed. Our results show that loss of centriolin/Cep110 leads to cell cycle arrest and apoptotic cell death in rhabdomyosarcoma cells. These findings suggest that centriolin/Cep110 plays a key role in rhabdomyosarcoma cell proliferation and viability and that this centrosome protein may represent a potential target for future rhabdomyosarcoma therapies.

The auxin system for inducible protein degradation is a powerful tool to investigate protein function. It consists of a degron fused to a target protein, an auxin-related ligand that binds to the degron, and a receptor that recognizes the auxin-bound degron and mediates proteasomal degradation of the target protein. Variants of all system components are available, and we here test three degrons, three auxins and three degron receptors to identify optimal combinations of these variants in budding yeast. We show that the degrons mIAA7 or AID* together with adamantyl-auxin and the degron receptor OsTIR1(F74G) allow particularly rapid and extensive degradation. Basal degradation in the absence of auxin is generally low and can be minimized further by inducible expression of OsTIR1(F74G). Moreover, we demonstrate that the remarkable efficiency of this system makes it competitive with established chemical inhibitors, such as tunicamycin and MG132, and with temperature-sensitive conditional alleles. These findings will aid the effective application of the auxin system.

From stealthy infiltrators to blunt-force saboteurs, many human viruses--perhaps all-disrupt nuclear transport to control host gene expression, suppress immune responses, and redirect cellular resources toward their own replication. Among them, respiratory viruses stand out for their global impact and relentless evolution, from seasonal scourges to pandemic threats. Focusing on adenoviruses, influenza, rhinoviruses, RSV, and SARS-CoV-2, we explore a series of molecular case studies that reveal both shared strategies and the diverse molecular innovations these respiratory pathogens use to subvert the nuclear transport machinery. We organize these tactics into six recurring strategies: NPC docking and nuclear entry, inhibition of immune-factor import, hijacking nuclear protein transport and karyopherins, sabotage of host mRNA export, degradation of FG-Nups, and exploitation of mitotic nuclear envelope breakdown. These insights not only illuminate fundamental virus-host conflicts but may also point the way toward new therapeutic vulnerabilities in the viruses' attack strategies.

The maintenance of healthy mitochondria is essential to neuronal homeostasis. Mitophagy is a critical mechanism that degrades damaged mitochondria, and disruption of this process is associated with neurodegenerative disease. Previous work has shown that mammalian optineurin (OPTN), a gene mutated in familial forms of amyotrophic lateral sclerosis (ALS) and glaucoma, is an adaptor to recruit autophagy machinery to mitochondria for ubiquitin-dependent mitophagy in cultured cells. However, OPTN's role in neuronal mitophagy in vivo remains largely unknown. Here, we demonstrate that the Drosophila autophagy adaptor gene Kenny, a homologue of OPTN, mediates the recruitment of the phagophore to mitochondria undergoing ubiquitin-dependent mitophagy. We find that Kenny colocalizes with ubiquitinated mitochondria targeted for autophagic degradation in larval motoneurons, and is concentrated on the mitochondrial surface in areas opposed to the phagophore. Removal of Kenny in conditions of induced mitophagy eliminates the recruitment of the phagophore to ubiquitinated mitochondria and decreases mitophagic flux. In basal conditions, loss of Kenny causes accumulation of ubiquitinated mitochondria in neurons, indicative of stalled mitophagy. These phenotypes were reproduced in Kenny mutants, ablating the LC3-interacting region domain. Overall, this work establishes Kenny as a functional homologue of OPTN in flies and a mediator of neuronal mitophagy in vivo.

Activation of the cGAS-STING pathway stimulates innate immune signaling as well as LC3B lipidation and ubiquitylation at Golgi-related vesicles upon STING trafficking. Although ubiquitylation at these subcellular sites has been associated with regulating NF-κB-related innate immune signaling, the mechanisms of Golgi-localized polyubiquitin chain regulation of immune signaling are not well understood. We report here that the ubiquitin- and LC3B-binding proteins, TNIP1 and autophagy receptors p62, NBR1, NDP52, TAX1BP1, and OPTN, associate with STING-induced ubiquitin and LC3B-labeled vesicles, and that p62 and NBR1 act redundantly in spatial clustering of the LC3B-labeled vesicles in the perinuclear region. We also find that while TBK1 kinase activity is not required for the recruitment of TNIP1 and the autophagy receptors, it plays a role in the sequestration of the LC3B-labeled vesicles. The ubiquitin binding domains, rather than the LC3-interacting regions, of TNIP1 and OPTN are specifically important for their recruitment to Ub/LC3B-associated perinuclear vesicles, and OPTN is also recruited through a TBK1-dependent mechanism. Functionally, we find that TNIP1 plays a role in STING-mediated innate immune signaling, acting as a negative regulator of IRF3-mediated gene expression. Together, these results highlight autophagy-independent mechanisms of autophagy receptors and TNIP1 with unanticipated roles in regulating STING-mediated innate immunity.

Promyelocytic leukemia (PML) protein isoform II is a component of PML nuclear bodies (PML NBs) that also forms patches on nuclear lipid droplets (nLDs) and the inner nuclear membrane (INM). Here we tested whether different metabolic treatments that induce membrane curvature elastic stress (CES) in the INM, detected by recruitment of CTP:phosphocholine cytidylyltransferase α (CCTα) and a nuclear diacylglycerol (DAG) biosensor, are a precondition for PML-II membrane association. We found that treatment of U2OS cells with unsaturated 18-carbon fatty acids and DAG acyltransferase inhibitors caused the rapid formation of PML patches on the INM that coincided with DAG enrichment and the recruitment and stabilization of CCTα, all of which were reversed upon removal of the CES stimulus. PML patches were depleted of canonical PML NB-associated proteins, occurred at sites of lamin depletion, were specific for the PML-II isoform, and occurred in cells regardless of their capacity to assemble nLDs. Induction of INM curvature stress by knockout of the terminal enzymes of the CDP-choline pathway or lipid activators of CCTα also promoted PML patches as well as stabilization of CCTα on the INM. We conclude that CES in the INM promotes the reversible assembly of PML-II-dependent membrane-associated patches.

Paralogs engage in biological processes through both redundant and nonredundant functions. In the yeast Saccharomyces cerevisiae, approximately one-fifth of the genome consists of paralogs, with their encoded proteins involved in multiple pathways. However, the unique contributions of individual paralogs have remained poorly defined. Here, we undertook a systematic examination of eight paralog pairs in the glucose-sensing pathways, deleting each component and measuring the resulting changes in gene expression. To that end, we established a new transcription reporter system to monitor the response to glucose as well as to nonpreferred sugars in single cells. Focusing on the PKA catalytic subunits, comprised of the paralogs Tpk1 and Tpk3 as well as the isomorphic kinase Tpk2, we employed mass spectrometry to identify their contribution to cellular metabolism, used a GFP-based sensor to follow changes in cytosolic pH, and used BioID to identify unique and shared candidate binding partners. Our data reveal that paralogs in the glucose-sensing pathway contribute in multiple and unique ways to signal transduction, and establish potential mechanisms driving the preservation of these and other duplicated genes throughout long periods of evolution.

Motor protein tails, long considered flexible and disordered linkers that mediate transient cargo interactions, are increasingly recognized as dynamic hubs containing context-dependent structural motifs. Advances in cryo-EM single-particle analysis, flexible refinement tools, and in situ cryo-ET now allow visualization of partially ordered elements within these flexible regions. Recent studies of kinesin reveal that local folding events regulate adaptor binding, cargo recognition, and motor activation, challenging the traditional view of the kinesin tail as mostly disordered. This emerging perspective highlights motor tails as regulatory platforms where intrinsic disorder coexists with hidden structure, reshaping our understanding of transport regulation.