Clathrin-associated carriers enable recycling through a kiss-and-run mechanism.

Endocytosis and recycling control the uptake and retrieval of various materials, including membrane proteins and lipids, in all eukaryotic cells. These processes are crucial for cell growth, organization, function and environmental communication. However, the mechanisms underlying efficient, fast endocytic recycling remain poorly understood. Here, by utilizing a biosensor and imaging-based screening, we uncover a recycling mechanism that couples endocytosis and fast recycling, which we name the clathrin-associated fast endosomal recycling pathway (CARP). Clathrin-associated tubulovesicular carriers containing clathrin, AP1, Arf1, Rab1 and Rab11, while lacking the multimeric retrieval complexes, are generated at subdomains of early endosomes and then transported along actin to cell surfaces. Unexpectedly, the clathrin-associated recycling carriers undergo partial fusion with the plasma membrane. Subsequently, they are released from the membrane by dynamin and re-enter cells. Multiple receptors utilize and modulate CARP for fast recycling following endocytosis. Thus, CARP represents a previously unrecognized endocytic recycling mechanism with kiss-and-run membrane fusion.

EZH2-H3K27me3-mediated silencing of mir-139-5p inhibits cellular senescence in hepatocellular carcinoma by activating TOP2A.

BACKGROUND: Epigenetic alterations play an important role in hepatocellular carcinoma (HCC) development. Enhancer of zeste homolog 2 (EZH2) is a well-known epigenetic modifier that functions as an oncogene in tumors by promoting the H3K27me3-mediated transcriptional repression of tumor suppressor genes. "Senescent cells" has been proposed as a possible core component of the hallmarks of cancer conceptualization. Induction of cell senescence and targeted elimination of these senescent tumor cells are new strategies for tumor therapy. However, the role of EZH2 in regulating cellular senescence remains poorly understood. METHODS: Bioinformatics analyses suggested that EZH2 and DNA topoisomerase II alpha (TOP2A) are coexpressed in tumors, including HCC. Kyoto Encyclopedia of Genes and Genome (KEGG) pathway enrichment analyses and gene set enrichment analyses (GSEA) suggests a correlation of EZH2 and TOP2A expression with cellular senescence in HCC. MicroRNA (miRNA) inhibitor and mimics, siRNA, PLKO-shRNA, and plenti6.3-miR-139 were used to upregulate or downregulate the expression of target genes. CCK8, EdU, clone formation, and senescence-associated ß-galactosidase (SA-ß-gal) staining assays were performed to assess cell proliferation and cellular senescence phenotypes. Dual-luciferase reporter and chromatin immunoprecipitation assays were performed to investigate the targeted binding and inhibition of TOP2A 3' untranslated region (UTR) by miR-139-5p and the DNA enrichment of miR139-5p by EZH2 and H3K27me3. BALB/c nude mice were used to establish a xenograft tumor model and verify the phenotypes upon EZH2 and TOP2A silencing and miR-139 overexpression in vivo. In addition, tissue microarrays were used to analyze the expression patterns and correlations among EZH2, TOP2A, and miR-139-5p expression in HCC. RESULTS: Bioinformatics analysis revealed that EZH2 and TOP2A are coexpressed in HCC. In vitro gain- and loss-of-function experiments showed that inhibition of EZH2 and TOP2A induces cellular senescence and inhibits proliferation of HCC cells. In vivo tumorigenesis assays indicated that EZH2 and TOP2A knockdown inhibits tumorigenesis by inducing cellular senescence. Mechanistically, EZH2 promotes TOP2A expression by regulating the H3K27me3-mediated epigenetic silencing of miR-139-5p. TOP2A is a direct target of miR-139-5p, and inhibition of miR-139-5p can reverse the promotion by EZH2 of TOP2A expression. The overexpression of miR-139-5p induces cellular senescence and inhibits proliferation of HCC cells both in vitro and in vivo. Clinically, expression of EZH2 and TOP2A are higher in HCC tissues than in normal tissues, and this high coexpression indicates a worse outcome of patients with HCC. Moreover, expression of EZH2 and TOP2A is significantly correlated with tumor differentiation grade, tumor invasion, and TNM stage in HCC. miR-139-5p expression is lower in HCC tumors than in normal tissues and is correlated with better prognosis of HCC patients. CONCLUSIONS: Our study revealed the role of the EZH2/miR-139-5p/TOP2A axis in regulating cellular senescence and cell proliferation in HCC, enriching the molecular mechanisms of EZH2-mediated epigenetic regulation in HCC. Therefore, our results provide insight into the therapeutic potential of targeting EZH2 to induce cellular senescence and then destroy senescent cells for HCC.

Finding the minimum number of retrieved lymph nodes in node-negative colorectal cancer using Real-world Data and the SEER database.

BACKGROUND: Current clinical guidelines recommend the removal of at least 12 lymph nodes (LNs) in resectable colorectal cancer (CRC). With advancements in lymphadenectomy technologies, the number of retrieved lymph nodes (rLNs) has markedly increased. This study aimed to investigate the lowest number of rLNs in node-negative patients. MATERIALS AND METHODS: A total of 1103 N0 and 208 N1a stage patients were enrolled in our cohort, while 8503 N0 and 1276 N1a patients from the Surveillance, Epidemiology, and End Results CRC database were included. Propensity score matching and multivariate Cox regression analyses were performed to mitigate the influence of selection bias and control for potential confounding variables. RESULTS: The median number of rLNs in N0 patients increased from 13.5 (interquartile range [IQR]: 9-18) in 2013 to 17 (IQR: 15-20) in 2019. The restrictive cubic spline illustrated a nonlinear relationship between rLNs and prognosis (nonlinearity, P =0.009), with a threshold ( N =16) influencing clinical outcomes. Patients at either N0 or N1a stage with sufficient rLNs (≥16) demonstrated superior prognoses to those with a limited rLNs (<16). After adjusting for clinical confounders, similar prognoses were observed in N0 limited and N1a adequate populations. Furthermore, Kaplan-Meier curves revealed that N0 limited patients who received chemotherapy exhibited better outcomes than those who did not. CONCLUSIONS: Among patients with node-negative CRC, it is crucial to remove 16 or more LNs effectively. Fewer than 16 rLNs should be regarded as an independent risk factor, implying the need for adjuvant chemotherapy.

The protocol of tagging endogenous proteins with fluorescent tags using CRISPR-Cas9 genome editing.

The currently widely used CRISPR-Cas9 genome editing technology enables the editing of target genes (knock-out or knock-in) with high accuracy and efficiency. Guided by the small guide RNA, the Cas9 nuclease induces a DNA double-strand break at the targeted genomic locus. The DNA double-strand break can be repaired by the homology-directed repair pathway in the presence of a repair template. With the repair template containing the coding sequence of a fluorescent tag, the targeted gene can be inserted with the sequence of a fluorescent tag at the designed position. The genome editing mediated labeling of endogenous proteins with fluorescent tags avoids the potential artifacts caused by gene overexpression and substantially improves the reproductivity of imaging experiments. This protocol focuses on creating mammalian cell lines with endogenous proteins tagged with fluorescent proteins or self-labeling protein tags using CRISPR-Cas9 genome editing.

Structure and dynamics of the EGFR/HER2 heterodimer.

HER2 belongs to the human epidermal growth factor receptor tyrosine kinase family. Its overexpression or hyperactivation is a leading cause for multiple types of cancers. HER2 functions mainly through dimerization with other family members, such as EGFR. However, the molecular details for heterodimer assembly have not been completely understood. Here, we report cryo-EM structures of the EGF- and epiregulin-bound EGFR/HER2 ectodomain complexes at resolutions of 3.3 Å and 4.5 Å, respectively. Together with the functional analyses, we demonstrate that only the dimerization arm of HER2, but not that of EGFR, is essential for their heterodimer formation and signal transduction. Moreover, we analyze the differential membrane dynamics and transient interactions of endogenous EGFR and HER2 molecules in genome-edited cells using single-molecule live-cell imaging. Furthermore, we show that the interaction with HER2 could allow EGFR to resist endocytosis. Together, this work deepens our understanding of the unique structural properties and dynamics of the EGFR/HER2 complex.

Identification of a hypoxia-related gene prognostic signature in colorectal cancer based on bulk and single-cell RNA-seq.

Colorectal cancer (CRC) is the most common and fatal tumor in the gastrointestinal system. Its incidence and mortality rate have increased in recent years. Hypoxia, a persistent physiological tumor feature, plays a vital role in CRC tumorigenesis, metastasis, and tumor microenvironment (TME). Therefore, we constructed a hypoxia-related gene (HRG) nomogram to predict overall survival (OS) and explored the role of HRGs in the CRC TME. The Cancer Genome Atlas (TCGA) dataset was used as the training set, and two Gene Expression Omnibus datasets (GSE39582 and GSE103479) were used as the testing sets. HRGs were identified using the Gene Set Enrichment Analysis (GSEA) database. An HRG prognostic model was constructed in the training set using the least absolute shrinkage and selection operator regression algorithm and validated in the testing sets. Then, we analyzed tumor-infiltrating cells (TICs) using the cell-type identification by estimating relative subsets of RNA transcripts (CIBERSORT) algorithm. Furthermore, single-cell next-generation RNA sequencing (RNA-seq) was used to investigate HRG expression in different TICs in the GSE139555 dataset. Finally, reverse transcription polymerase chain reactions (RT-PCR) were used to validate HRG mRNA expression in ten pairs of CRC normal and cancer tissue samples. A six HRG prognostic signature was constructed, with a superior OS prediction ability in CRC patients (area under the receiver operating characteristic curve (AUC) at one year: 0.693, AUC at three years: 0.712, and AUC at five years: 0.780). GSEA enrichment analysis identified six pathways enriched in the high-risk group. The TIC analysis indicated that the high-risk group had lower T-cell expression and higher neutrophil expression than the low-risk group. Furthermore, immune-related genes had an inseparable relationship with the HRG prognostic signature. Based on single-cell RNA-seq data, we found elevated hexokinase 1 (HK1) and glucose-6-phosphate isomerase (GPI) gene expression in natural killer (NK) and CD8+ T cells. RT-PCR in ten CRC normal-tumor tissue pairs showed that expression of the signature's six HRGs varied differently in cancerous and paracancerous tissues. The constructed HRG signature successfully predicted the OS of whole-stage CRC patients. In addition, we showed that the signature's six HRGs were closely associated with the TME in CRC, where hypoxia inhibits the antitumor function of T cells.

Overexpression of TaCOMT Improves Melatonin Production and Enhances Drought Tolerance in Transgenic Arabidopsis.

Melatonin (N-acetyl-5-methoxytryptamine) is involved in many developmental processes and responses to various abiotic stresses in plants. Most of the studies on melatonin focus on its functions and physiological responses in plants, while its regulation mechanism remains unknown. Caffeic acid 3-O-methyltransferase (COMT) functions at a key step of the biosynthesis process of melatonin. In this study, a COMT-like gene, TaCOMT (Traes_1AL_D9035D5E0.1) was identified in common wheat (Triticum aestivum L.). Transient transformation in wheat protoplasts determined that TaCOMT is localized in cytoplasm. TaCOMT in wheat was induced by drought stress, gibberellin (GA)3 and 3-Indoleacetic acid (IAA), but not by ABA. In TaCOMT transgenic Arabidopsis, melatonin contents were higher than that in wild type (WT) plants. Under D-Mannitol treatment, the fresh weight of the transgenic Arabidopsis was significantly higher than WT, and transgenic lines had a stronger root system compared to WT. Drought tolerance assays in pots showed that the survival rate of TaCOMT-overexpression lines was significantly higher than that of WT lines. this phenotype was similar to that the WT lines treated with melatonin under drought condition. In addition, the TaCOMT transgenic lines had higher proline content and lower malondialdehyde (MDA) content compared to WT lines after drought treatment. These results indicated that overexpression of the wheat TaCOMT gene enhances drought tolerance and increases the content of melatonin in transgenic Arabidopsis. It could be one of the potential genes for agricultural applications.

Identification and characterization of GmMYB118 responses to drought and salt stress.

BACKGROUND: Abiotic stress severely influences plant growth and development. MYB transcription factors (TFs), which compose one of the largest TF families, play an important role in abiotic stress responses. RESULT: We identified 139 soybean MYB-related genes; these genes were divided into six groups based on their conserved domain and were distributed among 20 chromosomes (Chrs). Quantitative real-time PCR (qRT-PCR) indicated that GmMYB118 highly responsive to drought, salt and high temperature stress; thus, this gene was selected for further analysis. Subcellular localization revealed that the GmMYB118 protein located in the nucleus. Ectopic expression (EX) of GmMYB118 increased tolerance to drought and salt stress and regulated the expression of several stress-associated genes in transgenic Arabidopsis plants. Similarly, GmMYB118-overexpressing (OE) soybean plants generated via Agrobacterium rhizogenes (A. rhizogenes)-mediated transformation of the hairy roots showed improved drought and salt tolerance. Furthermore, compared with the control (CK) plants, the clustered, regularly interspaced, short palindromic repeat (CRISPR)-transformed plants exhibited reduced drought and salt tolerance. The contents of proline and chlorophyll in the OE plants were significantly greater than those in the CK plants, whose contents were greater than those in the CRISPR plants under drought and salt stress conditions. In contrast, the reactive oxygen species (ROS) and malondialdehyde (MDA) contents were significantly lower in the OE plants than in the CK plants, whose contents were lower than those in the CRISPR plants under stress conditions. CONCLUSIONS: These results indicated that GmMYB118 could improve tolerance to drought and salt stress by promoting expression of stress-associated genes and regulating osmotic and oxidizing substances to maintain cell homeostasis.

The WRKY Transcription Factor GmWRKY12 Confers Drought and Salt Tolerance in Soybean.

WRKYs are important regulators in plant development and stress responses. However, knowledge of this superfamily in soybean is limited. In this study, we characterized the drought- and salt-induced gene GmWRKY12 based on RNA-Seq and qRT-PCR. GmWRKY12, which is 714 bp in length, encoded 237 amino acids and grouped into WRKY II. The promoter region of GmWRKY12 included ABER4, MYB, MYC, GT-1, W-box and DPBF cis-elements, which possibly participate in abscisic acid (ABA), drought and salt stress responses. GmWRKY12 was minimally expressed in different tissues under normal conditions but highly expressed under drought and salt treatments. As a nucleus protein, GmWRKY12 was responsive to drought, salt, ABA and salicylic acid (SA) stresses. Using a transgenic hairy root assay, we further characterized the roles of GmWRKY12 in abiotic stress tolerance. Compared with control (Williams 82), overexpression of GmWRKY12 enhanced drought and salt tolerance, increased proline (Pro) content and decreased malondialdehyde (MDA) content under drought and salt treatment in transgenic soybean seedlings. These results may provide a basis to understand the functions of GmWRKY12 in abiotic stress responses in soybean.

Wheat CBL-interacting protein kinase 23 positively regulates drought stress and ABA responses.

BACKGROUND: The calcineurin B-like protein (CBL)-interacting protein kinase (CIPK) signaling pathway responds to various abiotic stresses in plants. RESULTS: Wheat CIPK23, isolated from wheat drought transcriptome data set, was induced by multiple abiotic stresses, including drought, salt, and abscisic acid (ABA). Compared with wild-type plants, TaCIPK23-overexpression wheat and Arabidopsis showed an higher survival rate under drought conditions with enhanced germination rate, developed root system, increased accumulation of osmolytes, and reduced water loss rate. Over-expression of TaCIPK23 rendered transgenic plants ABA sensitivity, as evidenced by delayed seed germination and the induction of stomatal closure. Consistent with the ABA-sensitive phenotype, the expression level of drought- and ABA-responsive genes were increased under drought conditions in the transgenic plants. In addition, using yeast two-hybrid system, pull-down and bimolecular fluorescence complementation (BiFc) assays, TaCIPK23 was found to interact with TaCBL1 on the plasma membrane. CONCLUSIONS: These results suggest that TaCIPK23 plays important roles in ABA and drought stress responses, and mediates crosstalk between the ABA signaling pathway and drought stress responses in wheat.

Toxicological responses of the earthworm Eisenia fetida to 18-crown-6 under laboratory conditions.

The earthworm Eisenia fetida was exposed to artificial soil supplemented with 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) to investigate its effects on earthworm mortality, growth, avoidance, burrowing behavior and respiration. The results revealed that 18-crown-6 had the potential to negatively affect the behavior of earthworms. The 7-d LC50 was 585 mg kg(-1) soil. Avoidance behavior was the most sensitive endpoint, with a 48-h EC50 of 120 mg kg(-1) soil. Growth, burrow length and respiration showed general decreases with increasing 18-crown-6 concentrations. Behavioral endpoints and respiration may be regarded as sensitive parameters in evaluating the toxicity of this chemical to earthworms.