Search results for "Active transport"
showing 10 items of 80 documents
Activation of a nuclear-localized SIPK in tobacco cells challenged by cryptogein, an elicitor of plant defence reactions.
2009
When a plant cell is challenged by a well-defined stimulus, complex signal transduction pathways are activated to promote the modulation of specific sets of genes and eventually to develop adaptive responses. In this context, protein phosphorylation plays a fundamental role through the activation of multiple protein kinase families. Although the involvement of protein kinases at the plasma membrane and cytosolic levels are now well-documented, their nuclear counterparts are still poorly investigated. In the field of plant defence reactions, no known study has yet reported the activation of a nuclear protein kinase and/or its nuclear activity in plant cells, although some protein kinases, e.…
A Thermodynamic Model of Monovalent Cation Homeostasis in the Yeast Saccharomyces cerevisiae
2016
Cationic and heavy metal toxicity is involved in a substantial number of diseases in mammals and crop plants. Therefore, the understanding of tightly regulated transporter activities, as well as conceiving the interplay of regulatory mechanisms, is of substantial interest. A generalized thermodynamic description is developed for the complex interplay of the plasma membrane ion transporters, membrane potential and the consumption of energy for maintaining and restoring specific intracellular cation concentrations. This concept is applied to the homeostasis of cation concentrations in the yeast cells of S. cerevisiae. The thermodynamic approach allows to model passive ion fluxes driven by the…
BAX inhibitor-1 is a Ca(2+) channel critically important for immune cell function and survival.
2015
The endoplasmic reticulum (ER) serves as the major intracellular Ca(2+) store and has a role in the synthesis and folding of proteins. BAX (BCL2-associated X protein) inhibitor-1 (BI-1) is a Ca(2+) leak channel also implicated in the response against protein misfolding, thereby connecting the Ca(2+) store and protein-folding functions of the ER. We found that BI-1-deficient mice suffer from leukopenia and erythrocytosis, have an increased number of splenic marginal zone B cells and higher abundance and nuclear translocation of NF-κB (nuclear factor-κ light-chain enhancer of activated B cells) proteins, correlating with increased cytosolic and ER Ca(2+) levels. When put into culture, purifie…
Beyond the Transport Function of Import Receptors: What’s All the FUS about?
2018
Nuclear import receptors are central players in transporting protein cargoes into the nucleus. Moving beyond this role, four newly published articles describe a function in regulating supramolecular assemblies by fine-tuning the phase separating properties of RNA-binding proteins, which has implications for a variety of devastating neurodegenerative disorders.
Hypoxia-Induced miR-675-5p Supports β-Catenin Nuclear Localization by Regulating GSK3-β Activity in Colorectal Cancer Cell Lines
2020
The reduction of oxygen partial pressure in growing tumors triggers numerous survival strategies driven by the transcription factor complex HIF1 (Hypoxia Inducible Factor-1). Recent evidence revealed that HIF1 promotes rapid and effective phenotypic changes through the induction of non-coding RNAs, whose contribution has not yet been fully described. Here we investigated the role of the hypoxia-induced, long non-coding RNA H19 (lncH19) and its intragenic miRNA (miR-675-5p) into HIF1-Wnt crosstalk. During hypoxic stimulation, colorectal cancer cell lines up-regulated the levels of both the lncH19 and its intragenic miR-675-5p. Loss of expression experiments revealed that miR-675-5p inhibitio…
Iwr1 facilitates RNA polymerase II dynamics during transcription elongation.
2017
Iwr1 is an RNA polymerase II (RNPII) interacting protein that directs nuclear import of the enzyme which has been previously assembled in the cytoplasm. Here we present genetic and molecular evidence that links Iwr1 with transcription. Our results indicate that Iwr1 interacts with RNPII during elongation and is involved in the disassembly of the enzyme from chromatin. This function is especially important in resolving problems posed by damage-arrested RNPII, as shown by the sensitivity of iwr1 mutants to genotoxic drugs and the Iwr1's genetic interactions with RNPII degradation pathway mutants. Moreover, absence of Iwr1 causes genome instability that is enhanced by defects in the DNA repair…
Transport of Amino Acids Across the Blood-Brain Barrier.
2020
The blood-brain-barrier (BBB), present in brain capillaries, constitutes an essential barrier mechanism for normal functioning and development of the brain. The presence of tight junctions between adjacent endothelial cells restricts permeability and movement of molecules between extracellular fluid and plasma. The protein complexes that control cell-cell attachment also polarize cellular membrane, so that it can be divided into luminal (blood-facing) and abluminal (brain) sides, and each solute that enters/leaves the brain must cross both membranes. Several amino acid (AA) transport systems with different distributions on both sides of the BBB have been described. In a broad sense, there a…
Viral highway to nucleus exposed by image correlation analyses.
2018
AbstractParvoviral genome translocation from the plasma membrane into the nucleus is a coordinated multistep process mediated by capsid proteins. We used fast confocal microscopy line scan imaging combined with image correlation methods including auto-, pair- and cross-correlation, and number and brightness analysis, to study the parvovirus entry pathway at the single-particle level in living cells. Our results show that the endosome-associated movement of virus particles fluctuates from fast to slow. Fast transit of single cytoplasmic capsids to the nuclear envelope is followed by slow movement of capsids and fast diffusion of capsid fragments in the nucleoplasm. The unique combination of …
Protoparvovirus Knocking at the Nuclear Door
2017
Protoparvoviruses target the nucleus due to their dependence on the cellular reproduction machinery during the replication and expression of their single-stranded DNA genome. In recent years, our understanding of the multistep process of the capsid nuclear import has improved, and led to the discovery of unique viral nuclear entry strategies. Preceded by endosomal transport, endosomal escape and microtubule-mediated movement to the vicinity of the nuclear envelope, the protoparvoviruses interact with the nuclear pore complexes. The capsids are transported actively across the nuclear pore complexes using nuclear import receptors. The nuclear import is sometimes accompanied by structural chan…
Different pathways for the nuclear import of yeast RNA polymerase II
2015
Recent studies suggest that RNA polymerase II (Pol II) has to be fully assembled before being imported into the nucleus, while other reports indicate a distinct mechanism to import large and small subunits. In yeast, Iwr1 binds to the holoenzyme assembled in the cytoplasm and directs its nuclear entry. However, as IWR1 is not an essential gene, Iwr1-independent pathway(s) for the nuclear import of Pol II must exist. In this paper, we investigate the transport into the nucleus of several large and small Pol II subunits in the mutants of genes involved in Pol II biogenesis. We also analyse subcellular localization in the presence of drugs that can potentially affect Pol II nuclear import. Our…