Regulation of the cytokinesis cleavage furrow by PKCε

Lipid Polarization during Cytokinesis

The plasma membrane of eukaryotic cells is composed of a large number of lipid species that are laterally segregated into functional domains as well as asymmetrically distributed between the outer and inner leaflets. Additionally, the spatial distribution and organization of these lipids dramatically change in response to various cellular states, such as cell division, differentiation, and apoptosis. Division of one cell into two daughter cells is one of the most fundamental requirements for the sustenance of growth in all living organisms. The successful completion of cytokinesis, the final stage of cell division, is critically dependent on the spatial distribution and organization of specific lipids. In this review, we discuss the properties of various lipid species associated with cytokinesis and the mechanisms involved in their polarization, including forward trafficking, endocytic recycling, local synthesis, and cortical flow models. The differences in lipid species requirements and distribution in mitotic vs. male meiotic cells will be discussed. We will concentrate on sphingolipids and phosphatidylinositols because their transbilayer organization and movement may be linked via the cytoskeleton and thus critically regulate various steps of cytokinesis.

Protective potential of miR-146a-5p and its underlying molecular mechanism in diverse cancers: a comprehensive meta-analysis and bioinformatics analysis

Background/aims

Studies have shown that miR-146a-5p was differentially expressed in diverse cancers, but the associations between miR-146a-5p expression and prognosis across multiple types of cancer as well its potential targets and downstream pathways have not been comprehensively analyzed. In this study, we performed the first meta-analysis of the prognostic value of miR-146a-5p expression in diverse malignancies and explored prospective targets of miR-146a-5p and related signaling pathways.

Methods

A thorough search for articles related to miR-146a-5p was performed, and RNA-seq data from The Cancer Genome Atlas (TCGA) and microarray data from gene expression omnibus profiles were used to collect information about the prognostic value of miR-146a-5p. A comprehensive meta-analysis was conducted. Twelve platforms in miRWalk 2.0 were applied to predict targets of miR-146a-5p. TCGA RNA-seq data were used to validate the inverse relationships between miR-146a-5p and its likely targets. Subsequently, gene ontology and pathway analyses were conducted using Funrich version 3.1.3. Potential protein–protein interaction (PPI) networks were constructed. Potential target genes of miR-146a-5p in lung cancer were validated by RT-qPCR.

Results

We included 10 articles in the meta-analysis. In a pooled analysis, the high miR-146a-5p expression group showed a better overall survival in solid cancers, particularly in reproductive system cancers and digestive system cancers. A total of 120 predicted target genes were included in a bioinformatics analysis. Five pathways involving phospholipase C (PLC) and aquaporins (AQPs) were the most significantly enriched Kyoto Encyclopedia of Genes and Genomes pathways. Moreover, the PPI network displayed the related signaling pathways and interactions among proteins. AQP1 and FYN were validated by RT-qPCR to be potential targets of miR-146a-5p in lung cancer.

Conclusion

There is a close link between high miR-146a-5p expression and better overall survival in 21 types of solid cancer, especially in reproductive system and digestive system cancers. Furthermore, miR-146a-5p could inhibit diverse malignancies by modulating pathways linked to PLC or AQPs. In summary, miR-146a-5p is a potential prognostic biomarker and therapeutic target for various cancers.

Atorvastatin Attenuates Myocardial Hypertrophy Induced by Chronic Intermittent Hypoxia In Vitro Partly through miR-31/PKCε Pathway

Atorvastatin is proven to ameliorate cardiac hypertrophy induced by chronic intermittent hypoxia (CIH). However, little is known about the mechanism by which atorvastatin modulates CIH-induced cardiac hypertrophy, and whether specific hypertrophyrelated microRNAs are involved in the modulation. MiR-31 plays key roles in the development of cardiac hypertrophy induced by ischemia/hypoxia. This study examined whether miR-31 was involved in the protective role of atorvastatin against CIH-induced myocardial hypertrophy. H9c2 cells were subjected to 8-h intermittent hypoxia per day in the presence or absence of atorvastatin for 5 days. The size of cardiomyocytes, and the expression of caspase 3 and miR-31 were determined by Western blotting and RT-PCR, respectively. MiR-31 mimic or Ro 31-8220, a specific inhibitor of protein kinase C epsilon (PKCε), was used to determine the role of miR-31 in the anti-hypertrophic effect of atorvastatin on cardiomyocytes. PKCε in the cardiomyocytes with miR-31 upregulation or downregulation was detected using RT-PCR and Western blotting. The results showed that CIH induced obvious enlargement of cardiomyocytes, which was paralleled with increased atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and slow/beta cardiac myosin heavy-chain (MYH7) mRNA levels. All these changes were reversed by the treatment with atorvastatin. Meanwhile, miR-31 was increased by CIH in vitro. Of note, the atorvastatin pretreatment significantly increased the mRNA and protein expression of PKCe and decreased that of miR-31. Moreover, overexpression of miR-31 abolished the anti-hypertrophic effect of atorvastatin on cardiomyocytes. Upregulation and downregulation of miR-31 respectively decreased and increased the mRNA and protein expression of PKCε. These results suggest that atorvastatin provides the cardioprotective effects against CIH probably via up-regulating PKCε and down-regulating miR-31.

Lipid Cell Biology: A Focus on Lipids in Cell Division

Cells depend on hugely diverse lipidomes for many functions. The actions and structural integrity of the plasma membrane and most organelles also critically depend on membranes and their lipid components. Despite the biological importance of lipids, our understanding of lipid engagement, especially the roles of lipid hydrophobic alkyl side chains, in key cellular processes is still developing. Emerging research has begun to dissect the importance of lipids in intricate events such as cell division. This review discusses how these structurally diverse biomolecules are spatially and temporally regulated during cell division, with a focus on cytokinesis. We analyze how lipids facilitate changes in cellular morphology during division and how they participate in key signaling events. We identify which cytokinesis proteins are associated with membranes, suggesting lipid interactions. More broadly, we highlight key unaddressed questions in lipid cell biology and techniques, including mass spectrometry, advanced imaging, and chemical biology, which will help us gain insights into the functional roles of lipids.

Proteomics Screen Identifies Class I Rab11 Family Interacting Proteins as Key Regulators of Cytokinesis

The 14-3-3 protein family orchestrates a complex network of molecular interactions that regulates various biological processes. Owing to their role in regulating the cell cycle and protein trafficking, 14-3-3 proteins are prevalent in human diseases such as cancer, diabetes, and neurodegeneration. 14-3-3 proteins are expressed in all eukaryotic cells, suggesting that they mediate their biological functions through evolutionarily conserved protein interactions. To identify these core 14-3-3 client proteins, we used an affinity-based proteomics approach to characterize and compare the human and Drosophila 14-3-3 interactomes. Using this approach, we identified a group of Rab11 effector proteins, termed class I Rab11 family interacting proteins (Rab11-FIPs), or Rip11 in Drosophila We found that 14-3-3 binds to Rip11 in a phospho-dependent manner to ensure its proper subcellular distribution during cell division. Our results indicate that Rip11 plays an essential role in the regulation of cytokinesis and that this function requires its association with 14-3-3 but not with Rab11. Together, our results suggest an evolutionarily conserved role for 14-3-3 in controlling Rip11-dependent protein transport during cytokinesis.