LUZP1 Controls Cell Division, Migration and Invasion Through Regulation of the Actin Cytoskeleton

LUZP1 regulates the maturation of contractile actomyosin bundles

Contractile actomyosin bundles play crucial roles in various physiological processes, including cell migration, morphogenesis, and muscle contraction. The intricate assembly of actomyosin bundles involves the precise alignment and fusion of myosin II filaments, yet the underlying mechanisms and factors involved in these processes remain elusive. Our study reveals that LUZP1 plays a central role in orchestrating the maturation of thick actomyosin bundles. Loss of LUZP1 caused abnormal cell morphogenesis, migration, and the ability to exert forces on the environment. Importantly, knockout of LUZP1 results in significant defects in the concatenation and persistent association of myosin II filaments, severely impairing the assembly of myosin II stacks. The disruption of these processes in LUZP1 knockout cells provides mechanistic insights into the defective assembly of thick ventral stress fibers and the associated cellular contractility abnormalities. Overall, these results significantly contribute to our understanding of the molecular mechanism involved in actomyosin bundle formation and highlight the essential role of LUZP1 in this process.

Leucine zipper protein 1 (LUZP1) regulates the constriction velocity of the contractile ring during cytokinesis

There has been a great deal of research on cell division and its mechanisms; however, its processes still have many unknowns. To find novel proteins that regulate cell division, we performed the screening using siRNAs and/or the expression plasmid of the target genes and identified leucine zipper protein 1 (LUZP1). Recent studies have shown that LUZP1 interacts with various proteins and stabilizes the actin cytoskeleton; however, the function of LUZP1 in mitosis is not known. In this study, we found that LUZP1 colocalized with the chromosomal passenger complex (CPC) at the centromere in metaphase and at the central spindle in anaphase and that these LUZP1 localizations were regulated by CPC activity and kinesin family member 20A (KIF20A). Mass spectrometry analysis identified that LUZP1 interacted with death-associated protein kinase 3 (DAPK3), one regulator of the cleavage furrow ingression in cytokinesis. In addition, we found that LUZP1 also interacted with myosin light chain 9 (MYL9), a substrate of DAPK3, and comprehensively inhibited MYL9 phosphorylation by DAPK3. In line with a known role for MYL9 in the actin-myosin contraction, LUZP1 suppression accelerated the constriction velocity at the division plane in our time-lapse analysis. Our study indicates that LUZP1 is a novel regulator for cytokinesis that regulates the constriction velocity of the contractile ring.

Identification cloning and functional analysis of novel natural antisense lncRNA CFL1-AS1 in cattle

Long noncoding RNAs have been identified as important regulators of gene expression and animal development. The expression of natural antisense transcripts (NATs) transcribed in the opposite direction to protein-coding genes is usually positively correlated with the expression of homologous sense genes and is the key factor for expression. Here, we identified a conserved noncoding antisense transcript, CFL1-AS1, that plays an important role in muscle growth and development. CFL1-AS1 overexpression and knockout vectors were constructed and transfected into 293T and C2C12 cells. CFL1-AS1 positively regulated CFL1 gene expression, and the expression of CFL2 was also downregulated when CFL1-AS1 was knocked down. CFL1-AS1 promoted cell proliferation, inhibited apoptosis and participated in autophagy. This study expands the research on NATs in cattle and lays a foundation for the study of the biological function of bovine CFL1 and its natural antisense chain transcript CFL1-AS1 in bovine skeletal muscle development. The discovery of this NAT can provide a reference for subsequent genetic breeding and data on the characteristics and functional mechanisms of NATs.

Single particle tracking reveals SARS-CoV-2 regulating and utilizing dynamic filopodia for viral invasion

Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry mechanism has been explored, little is known about how SARS-CoV-2 regulates the subcellular structural remodeling to invade multiple organs and cell types. Here, we unveil how SARS-CoV-2 boosts and utilizes filopodia to enter the target cells by real-time imaging. Using SARS-CoV-2 single virus-like particle (VLP) tracking in live cells and sparse deconvolution algorithm, we uncover that VLPs utilize filopodia to reach the entry site in two patterns, "surfing" and "grabbing", which avoid the virus from randomly searching on the plasma membrane. Moreover, combining mechanical simulation, we elucidate that the formation of virus-induced filopodia and the retraction speed of filopodia depend on cytoskeleton dynamics and friction resistance at the substrate surface caused by loading-virus gravity, respectively. Further, we discover that the entry process of SARS-CoV-2 via filopodia depends on Cdc42 activity and actin-associated proteins fascin, formin, and Arp2/3. Together, our results highlight that the spatial-temporal regulation of actin cytoskeleton by SARS-CoV-2 infection makes filopodia as a highway for virus entry and potentiates it as an antiviral target.

Nuclear Actin Polymerization Regulates Cell Epithelial-Mesenchymal Transition

Current studies on actin function primarily rely on cytoplasmic actin due to the absence of cellular models specifically expressing nuclear actin. Here, cell models capable of expressing varying levels of nuclear F/G-actin are generated and a significant role of nuclear actin in the regulation of epithelial-mesenchymal transition (EMT) is uncovered. Through immunoprecipitation and mass spectrometry analyses, distinct binding partners for nuclear F-actin (β-catenin, SMAD2, and SMAD3) and nuclear G-actin (MYBBP1A, NKRF, and MYPOP) are investigated, which respectively modulate EMT-promoting and EMT-repressing transcriptional events. While nuclear F-actin promotes EMT with enhanced cell migration, survival, and elongated mesenchymal morphology, nuclear G-actin represses EMT and related cell activities. Mechanistically, nuclear F-actin enhances β-catenin, SMAD2, and SMAD3 expression and stability in the nuclei, while nuclear G-actin increases MYBBP1A, NKRF, and MYPOP expression and stability in the nuclei. The association between nuclear F/G-actin and N-cadherin/E-cadherin in the cell lines (in vitro), and increased nuclear actin polymerization in the wound healing cells (in vivo) affirm a significant role of nuclear actin in EMT regulation. With evidence of nuclear actin polymerization and EMT during development, and irregularities in disease states such as cancer and fibrosis, targeting nuclear actin dynamics to trigger dysregulated EMT warrants ongoing study.

pPe Op inhibits HGC-27 cell proliferation, migration and invasion by upregulating miR-30b-5p and down-regulating the Rac1/Cdc42 pathway

Gastric cancer is the fifth most frequently occurring and the fourth most lethal malignant cancer worldwide. A bioactive protein (pPe Op) from Omphalia lapidescens exhibits significant inhibitory effects on gastric cancer cells. miRNA deep sequencing analysis shows that miR-30b-5p is significantly upregulated in HGC-27 cells treated with pPe Op. Verification results show that the expression level of miR-30b-5p is significantly increased in HGC-27 cells after pPe Op treatment. Additionally, miR-30b-5p is significantly downregulated in clinical gastric cancer tissues compared to that in adjacent normal tissues. Following pPe Op treatment and/or transfection with miR-30b-5p mimic, the proliferation, migration, and invasion of HGC-27 cells are significantly impaired. Immunofluorescence microscopy shows that pPe Op and/or miR-30b-5p destroy(s) microfilaments and microstructures and inhibit(s) the formation of pseudopodia. Bioinformatics analysis, dual-luciferase reporter assay, and western blot analysis confirm that miR-30b-5p downregulates Rac1/Cdc42 expression and activation by targeting RAB22A. Available data indicate that miR-30b-5p plays an anti-gastric cancer role in mediating pPe Op. pPe Op upregulates miR-30b-5p expression, which in turn inhibits RAB22A expression, resulting in a reduction in the expression and activation of Rac1 and Cdc42 and their downstream targets, thus destroying the cytoskeletal structure and inhibiting the proliferation, migration, and invasion of cancer cells.

Screening of co-pathogenic genes of non-alcoholic fatty liver disease and hepatocellular carcinoma

Background

Non-alcoholic fatty liver disease (NAFLD) is a risk factor for hepatocellular carcinoma (HCC). However, its carcinogenic mechanism is still unclear, looking for both diseases’ transcriptome levels, the same changes as we are looking for NAFLD may provide a potential mechanism of action of HCC. Thus, our study aimed to discover the coexisting pathogenic genes of NAFLD and HCC.

Methods

We performed a variance analysis with public data for both diseases. At the same time, weighted gene correlation network analysis (WGCNA) was used to find highly correlated gene modules in both diseases. The darkturquoise gene module was found to be highly correlated with both diseases. Based on the diagnosis related module genes and the differential genes of the two diseases, we constructed diagnostic and prognostic models by logistic regression, univariate Cox regression, and LASSO regression. Public datasets verified the results. Meanwhile, we built a competing endogenous RNA (ceRNA) network based on the model genes and explored the related pathways and immune correlation involved in the two diseases by using Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and gene set enrichment analyses. Immunohistochemistry was used to verify the different expression of ABCC5 and TUBG1 among the normal liver, NAFLD, and HCC tissues. Sodium palmitate/sodium oleate was used to establish high-fat cell models, and Real Time Quantitative Polymerase Chain Reaction (RT-qPCR) was used to verify the messenger RNA (mRNA) expression of ABCC5 in lipidization cells.

Results

A total of 26 upregulated genes and 87 downregulated genes were found using limma package identification analysis. According to WGCNA, the darkturquoise gene module was highly correlated with the prognosis of both diseases. The coexisting genes acquired by the two groups were only three central genes, that is, ABCC5, DHODH and TUBG1. The results indicated that the diagnostic and prognostic models constructed by ABCC5 and TUBG1 genes had high accuracy in both diseases. The results of immunohistochemistry showed that ABCC5 and TUBG1 were significantly overexpressed in NAFLD and HCC tissues compared with normal liver tissues. The Oil Red O staining and triglyceride identified the successful construction of HepG2 and LO2 high-fat models using PA/OA. The results of RT-qPCR showed that the lipidization of LO2 and HepG2 increased the mRNA expression of ABCC5.

Conclusions

The gene model constructed by ABCC5 and TUBG1 has high sensibility and veracity in the diagnosis of NAFLD as well as the diagnosis and prognosis of HCC. ABCC5 and TUBG1 may play an important role in the development of NAFLD to HCC. In addition, lipidization could upregulate the mRNA expression of ABCC5 in HCC.

LUZP1: A new player in the actin-microtubule cross-talk

LUZP1 (leucine zipper protein 1) was first described as being important for embryonic development. Luzp1 null mice present defective neural tube closure and cardiovascular problems, which cause perinatal death. Since then, LUZP1 has also been implicated in the etiology of diseases like the 1p36 and the Townes-Brocks syndromes, and the molecular mechanisms involving this protein started being uncovered. Proteomics studies placed LUZP1 in the interactomes of the centrosome-cilium interface, centriolar satellites, and midbody. Concordantly, LUZP1 is an actin and microtubule-associated protein, which localizes to the centrosome, the basal body of primary cilia, the midbody, actin filaments and cellular junctions. LUZP1, like its interactor EPLIN, is an actin-stabilizing protein and a negative regulator of primary cilia formation. Moreover, through the regulation of actin, LUZP1 has been implicated in the regulation of cell cycle progression, cell migration and epithelial cell apical constriction. This review discusses the latest findings concerning LUZP1 molecular functions and implications in disease development.

Proteomic Signatures of Diffuse and Intestinal Subtypes of Gastric Cancer

Gastric cancer is a leading cause of death from cancer globally. Gastric cancer is classified into intestinal, diffuse and indeterminate subtypes based on histology according to the Laurén classification. The intestinal and diffuse subtypes, although different in histology, demographics and outcomes, are still treated in the same fashion. This study was designed to discover proteomic signatures of diffuse and intestinal subtypes. Mass spectrometry-based proteomics using tandem mass tags (TMT)-based multiplexed analysis was used to identify proteins in tumor tissues from patients with diffuse or intestinal gastric cancer with adjacent normal tissue control. A total of 7448 or 4846 proteins were identified from intestinal or diffuse subtype, respectively. This quantitative mass spectrometric analysis defined a proteomic signature of differential expression across the two subtypes, which included gremlin1 (GREM1), bcl-2-associated athanogene 2 (BAG2), olfactomedin 4 (OLFM4), thyroid hormone receptor interacting protein 6 (TRIP6) and melanoma-associated antigen 9 (MAGE-A9) proteins. Although GREM1, BAG2, OLFM4, TRIP6 and MAGE-A9 have all been previously implicated in tumor progression and metastasis, they have not been linked to intestinal or diffuse subtypes of gastric cancer. Using immunohistochemical labelling of a tissue microarray comprising of 124 cases of gastric cancer, we validated the proteomic signature obtained by mass spectrometry in the discovery cohort. Our findings should help investigate the pathogenesis of these gastric cancer subtypes and potentially lead to strategies for early diagnosis and treatment.