Biological Chemistry最新文献

Growth cones of oligodendrocyte progenitor cells (OPCs) are challenging to investigate with conventional light microscopy due to their small size. Especially substructures such as filopodia, lamellipodia and their underlying cytoskeleton are difficult to resolve with diffraction limited microscopy. Light microscopy techniques, which surpass the diffraction limit such as stimulated emission depletion microscopy, often require expensive setups and specially trained personnel rendering them inaccessible to smaller research groups. Lately, the invention of expansion microscopy (ExM) has enabled super-resolution imaging with any light microscope without the need for additional equipment. Apart from the necessary resolution, investigating OPC growth cones comes with another challenge: Imaging the topography of membranes, especially label- and contact-free, is only possible with very few microscopy techniques one of them being scanning ion conductance microscopy (SICM). We here present a new imaging workflow combining SICM and ExM, which enables the visualization of OPC growth cone nanostructures. We correlated SICM recordings and ExM images of OPC growth cones captured with a conventional widefield microscope. This enabled the visualization of the growth cones' membrane topography as well as their underlying actin and tubulin cytoskeleton.

HnRNPs are ubiquitously expressed RNA-binding proteins, tightly controlling posttranscriptional gene regulation. Consequently, hnRNP networks are essential for cellular homeostasis and their dysregulation is associated with cancer and other diseases. However, the physiological function of hnRNPs in non-cancerous cell systems are poorly understood. We analyzed the importance of HNRNPDL in endothelial cell functions. Knockdown of HNRNPDL led to impaired proliferation, migration and sprouting of spheroids. Transcriptome analysis identified cyclin D1 (CCND1) and tropomyosin 4 (TPM4) as targets of HNRNPDL, reflecting the phenotypic changes after knockdown. Our findings underline the importance of HNRNPDL for the homeostasis of physiological processes in endothelial cells.

The prevention and treatment of gastric cancer has been the focus and difficulty of medical research. We aimed to explore the mechanism of inhibiting migration and invasion of gastric cancer cells by methionine restriction (MR). The human gastric cancer cell lines AGS and MKN45 cultured with complete medium (CM) or medium without methionine were used for in vitro experiments. MKN45 cells were injected tail vein into BALB/c nude mice and then fed with normal diet or methionine diet for in vivo experiments. MR treatment decreased cell migration and invasion, increased E-cadherin expression, decreased N-cadherin and p-p65 expressions, and inhibited nuclear p65 translocation of AGS and MKN45 cells when compared with CM group. MR treatment increased IκBα protein expression and protein stability, and decreased IκBα protein ubiquitination level and TRIM47 expression. TRIM47 interacted with IκBα protein, and overexpression of TRIM47 reversed the regulatory effects of MR. TRIM47 promoted lung metastasis formation and partially attenuated the effect of MR on metastasis formation in vivo compared to normal diet group mice. MR reduces TRIM47 expression, leads to the degradation of IκBα, and then inhibits the translocation of nuclear p65 and the migration and invasion of gastric cancer cells.

Platelet-derived growth factor (PDGF)-induced changes in vascular smooth muscle cells (VSMCs) stimulate vascular remodeling, resulting in vascular diseases such as pulmonary arterial hypertension. VSMCs communicate with endothelial cells through extracellular vesicles (EVs) carrying cargos, including microRNAs. To understand the molecular mechanisms through which PDGF-stimulated pulmonary artery smooth muscle cells (PASMCs) interact with pulmonary artery endothelial cells (PAECs) under pathological conditions, we investigated the crosstalk between PASMCs and PAECs via extracellular vesicle miR-409-5p under PDGF stimulation. miR-409-5p expression was upregulated in PASMCs upon PDGF signaling, and it was released into EVs. The elevated expression of miR-409-5p was transported to PAECs and led to their impaired function, including reduced NO release, which consequentially resulted in enhanced PASMC proliferation. We propose that the positive regulatory loop of PASMC-extracellular vesicle miR-409-5p-PAEC is a potential mechanism underlying the proliferation of PASMCs under PDGF stimulation. Therefore, miR-409-5p may be a novel therapeutic target for the treatment of vascular diseases, including pulmonary arterial hypertension.

Proteolytic activity in the tumour microenvironment is an important factor in cancer development since it can also affect intracellular signalling pathways via positive feedback loops that result in either increased tumour growth or resistance to anticancer mechanisms. In this study, we demonstrated extracellular cathepsin L-mediated cleavage of epidermal growth factor receptor (EGFR) and identified the cleavage site in the extracellular domain after R224. To further evaluate the relevance of this cleavage, we cloned and expressed a truncated version of EGFR, starting at G225, in HeLa cells. We confirmed the constitutive activation of the truncated protein in the absence of ligand binding and determined possible changes in intracellular signalling. Furthermore, we determined the effect of truncated EGFR protein expression on HeLa cell viability and response to the EGFR inhibitors, tyrosine kinase inhibitor (TKI) erlotinib and monoclonal antibody (mAb) cetuximab. Our data reveal the nuclear localization and phosphorylation of EGFR and signal trancducer and activator of transcription 3 (STAT3) in cells that express the truncated EGFR protein and suggest that these phenomena cause resistance to EGFR inhibitors.

Ribosomal RNAs (rRNAs) are structural components of ribosomes and represent the most abundant cellular RNA fraction. In the yeast Saccharomyces cerevisiae, they account for more than 60 % of the RNA content in a growing cell. The major amount of rRNA is synthesized by RNA polymerase I (Pol I). This enzyme transcribes exclusively the rRNA gene which is tandemly repeated in about 150 copies on chromosome XII. The high number of transcribed rRNA genes, the efficient recruitment of the transcription machinery and the dense packaging of elongating Pol I molecules on the gene ensure that enough rRNA is generated. Specific features of Pol I and of associated factors confer promoter selectivity and both elongation and termination competence. Many excellent reviews exist about the state of research about function and regulation of Pol I and how Pol I initiation complexes are assembled. In this report we focus on the Pol I specific lobe binding subunits which support efficient, error-free, and correctly terminated rRNA synthesis.

Retracing human cognitive origins started out at the systems level with the top-down interpretation of archaeological records spanning from man-made artifacts to endocasts of ancient skulls. With emerging evolutionary genetics and organoid technologies, it is now possible to deconstruct evolutionary processes on a molecular/cellular level from the bottom-up by functionally testing archaic alleles in experimental models. The current challenge is to complement these approaches with novel strategies that allow a holistic reconstruction of evolutionary patterns across human cognitive domains. We argue that computational neuroarcheology can provide such a critical mesoscale framework at the brain network-level, linking molecular/cellular (bottom-up) to systems (top-down) level data for the correlative archeology of the human mind.

Infections remain the most common cause of death after traumatic spinal cord injury, likely due to a developing immune deficiency syndrome. This, together with a somewhat contradictory development of autoimmunity in many patients, are two major components of the maladaptive systemic immune response. Although the local non-resolving inflammation in the lesioned spinal cord may lead to an antibody formation against autoantigens of the injured spinal cord tissue, there are also natural (pre-existing) autoantibodies independent of the injury. The way in which these autoantibodies with different origins affect the neuronal and functional outcome of spinal cord-injured patients is still controversial.

RNA binding proteins (RBPs) have multiple and essential roles in transcriptional and posttranscriptional regulation of gene expression in all living organisms. Their biochemical identification in the proteome of a given cell or tissue requires significant protein amounts, which limits studies in rare and highly specialized cells. As a consequence, we know almost nothing about the role(s) of RBPs in reproductive processes such as egg cell development, fertilization and early embryogenesis in flowering plants. To systematically identify the RBPome of egg cells in the model plant Arabidopsis, we performed RNA interactome capture (RIC) experiments using the egg cell-like RKD2-callus and were able to identify 728 proteins associated with poly(A⁺)-RNA. Transcripts for 97 % of identified proteins could be verified in the egg cell transcriptome. 46 % of identified proteins can be associated with the RNA life cycle. Proteins involved in mRNA binding, RNA processing and metabolism are highly enriched. Compared with the few available RBPome datasets of vegetative plant tissues, we identified 475 egg cell-enriched RBPs, which will now serve as a resource to study RBP function(s) during egg cell development, fertilization and early embryogenesis. First candidates were already identified showing an egg cell-specific expression pattern in ovules.