The V-ATPase a2-subunit as a putative endosomal pH-sensor

2007 ◽  
Vol 35 (5) ◽  
pp. 1092-1099 ◽  
Author(s):  
V. Marshansky
Keyword(s):  
Crucial Role ◽  
Molecular Mechanisms ◽  
Ph Sensor ◽  
Small Gtpases ◽  
Ph Sensitive ◽  
Ph Sensing ◽  
Degradative Pathway ◽  
Histidine Residues ◽  
Endosomal Acidification

V-ATPase (vesicular H+-ATPase)-driven intravesicular acidification is crucial for vesicular trafficking. Defects in vesicular acidification and trafficking have recently been recognized as essential determinants of various human diseases. An important role of endosomal acidification in receptor–ligand dissociation and in activation of lysosomal hydrolytic enzymes is well established. However, the molecular mechanisms by which luminal pH information is transmitted to the cytosolic small GTPases that control trafficking events such as budding, coat formation and fusion are unknown. Here, we discuss our recent discovery that endosomal V-ATPase is a pH-sensor regulating the degradative pathway. According to our model, V-ATPase is responsible for: (i) the generation of a pH gradient between vesicular membranes; (ii) sensing of intravesicular pH; and (iii) transmitting this information to the cytosolic side of the membrane. We also propose the hypothetical molecular mechanism involved in function of the V-ATPase a2-subunit as a putative pH-sensor. Based on extensive experimental evidence on the crucial role of histidine residues in the function of PSPs (pH-sensing proteins) in eukaryotic cells, we hypothesize that pH-sensitive histidine residues within the intra-endosomal loops and/or C-terminal luminal tail of the a2-subunit could also be involved in the pH-sensing function of V-ATPase. However, in order to identify putative pH-sensitive histidine residues and to test this hypothesis, it is absolutely essential that we increase our understanding of the folding and transmembrane topology of the a-subunit isoforms of V-ATPase. Thus the crucial role of intra-endosomal histidine residues in pH-dependent conformational changes of the V-ATPase a2-isoform, its interaction with cytosolic small GTPases and ultimately in its acidification-dependent regulation of the endosomal/lysosomal protein degradative pathway remain to be determined.

scholarly journals Vitamin D-Induced Molecular Mechanisms to Potentiate Cancer Therapy and to Reverse Drug-Resistance in Cancer Cells

Nutrients ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1798 ◽  
Author(s):  
Mariarosaria Negri ◽  
Annalisa Gentile ◽  
Cristina de Angelis ◽  
Tatiana Montò ◽  
Roberta Patalano ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Stem Cells ◽  
Vitamin D ◽  
Drug Resistance ◽  
Cancer Therapy ◽  
Cancer Stem Cells ◽  
Crucial Role ◽  
Molecular Mechanisms ◽  
Vitamin D Supplementation

Increasing interest in studying the role of vitamin D in cancer has been provided by the scientific literature during the last years, although mixed results have been reported. Vitamin D deficiency has been largely associated with various types of solid and non-solid human cancers, and the almost ubiquitous expression of vitamin D receptor (VDR) has always led to suppose a crucial role of vitamin D in cancer. However, the association between vitamin D levels and the risk of solid cancers, such as colorectal, prostate and breast cancer, shows several conflicting results that raise questions about the use of vitamin D supplements in cancer patients. Moreover, studies on vitamin D supplementation do not always show improvements in tumor progression and mortality risk, particularly for prostate and breast cancer. Conversely, several molecular studies are in agreement about the role of vitamin D in inhibiting tumor cell proliferation, growth and invasiveness, cell cycle arrest and inflammatory signaling, through which vitamin D may also regulate cancer microenvironment through the activation of different molecular pathways. More recently, a role in the regulation of cancer stem cells proliferation and short non-coding microRNA (miRNAs) expression has emerged, conferring to vitamin D a more crucial role in cancer development and progression. Interestingly, it has been shown that vitamin D is able not only to potentiate the effects of traditional cancer therapy but can even contribute to overcome the molecular mechanisms of drug resistance—often triggering tumor-spreading. At this regard, vitamin D can act at various levels through the regulation of growth of cancer stem cells and the epithelial–mesenchymal transition (EMT), as well as through the modulation of miRNA gene expression. The current review reconsiders epidemiological and molecular literature concerning the role of vitamin D in cancer risk and tumor development and progression, as well as the action of vitamin D supplementation in potentiating the effects of drug therapy and overcoming the mechanisms of resistance often triggered during cancer therapies, by critically addressing strengths and weaknesses of available data from 2010 to 2020.

scholarly journals Role of LAMP1 Binding and pH Sensing by the Spike Complex of Lassa Virus

2016 ◽  
Vol 90 (22) ◽  
pp. 10329-10338 ◽  
Author(s):  
Hadas Cohen-Dvashi ◽  
Hadar Israeli ◽  
Orly Shani ◽  
Aliza Katz ◽  
Ron Diskin
Keyword(s):  
Membrane Fusion ◽  
Molecular Mechanisms ◽  
Cell Entry ◽  
Lassa Virus ◽  
Dependent Manner ◽  
Acidic Ph ◽  
Ph Sensing ◽  
Positively Charged

ABSTRACTTo effectively infect cells, Lassa virus needs to switch in an endosomal compartment from its primary receptor, α-dystroglycan, to a protein termed LAMP1. A unique histidine triad on the surface of the receptor-binding domain from the glycoprotein spike complex of Lassa virus is important for LAMP1 binding. Here we investigate mutated spikes that have an impaired ability to interact with LAMP1 and show that although LAMP1 is important for efficient infectivity, it is not required for spike-mediated membrane fusionper se. Our studies reveal important regulatory roles for histidines from the triad in sensing acidic pH and preventing premature spike triggering. We further show that LAMP1 requires a positively charged His230 residue to engage with the spike complex and that LAMP1 binding promotes membrane fusion. These results elucidate the molecular role of LAMP1 binding during Lassa virus cell entry and provide new insights into how pH is sensed by the spike.IMPORTANCELassa virus is a devastating disease-causing agent in West Africa, with a significant yearly death toll and severe long-term complications associated with its infection in survivors. In recent years, we learned that Lassa virus needs to switch receptors in a pH-dependent manner to efficiently infect cells, but neither the molecular mechanisms that allow switching nor the actual effects of switching were known. Here we investigate the activity of the viral spike complex after abrogation of its ability to switch receptors. These studies inform us about the role of switching receptors and provide new insights into how the spike senses acidic pH.

Impact of the FcγII-receptor on quartz uptake and inflammatory response by alveolar macrophages

2008 ◽  
Vol 294 (6) ◽  
pp. L1137-L1148 ◽  
Author(s):  
Petra Haberzettl ◽  
Roel P. F. Schins ◽  
Doris Höhr ◽  
Verena Wilhelmi ◽  
Paul J. A. Borm ◽  
...  
Keyword(s):  
Inflammatory Response ◽  
Alveolar Macrophages ◽  
Tyrosine Kinases ◽  
Molecular Mechanisms ◽  
Morphological Changes ◽  
Inhibitory Effect ◽  
Small Gtpases ◽  
Downstream Signaling ◽  
Particle Uptake

The inflammatory response following particle inhalation is described as a key event in the development of lung diseases, e.g., fibrosis and cancer. The essential role of alveolar macrophages (AM) in the pathogenicity of particles through their functions in lung clearance and mediation of inflammation is well known. However, the molecular mechanisms and direct consequences of particle uptake are still unclear. Inhibition of different classic phagocytosis receptors by flow cytometry shows a reduction of the dose-dependent quartz particle (DQ12) uptake in the rat AM cell line NR8383. Thereby the strongest inhibitory effect was observed by blocking the FcγII-receptor (FcγII-R). Fluorescence immunocytochemistry, demonstrating FcγII-R clustering at particle binding sites as well as transmission electron microscopy, visualizing zippering mechanism-like morphological changes, confirmed the role of the FcγII-R in DQ12 phagocytosis. FcγII-R participation in DQ12 uptake was further strengthened by the quartz-induced activation of the Src-kinase Lyn, the phospho-tyrosine kinases Syk (spleen tyrosine kinase) and PI3K (phosphatidylinositol 3-kinase), as shown by Western blotting. Activation of the small GTPases Rac1 and Cdc42, shown by immunoprecipitation, as well as inhibition of tyrosine kinases, GTPases, or Rac1 provided further support for the role of the FcγII-R. Consistent with the uptake results, FcγII-R activation with its specific ligand caused a similar generation of reactive oxygen species and TNF-α release as observed after treatment with DQ12. In conclusion, our results indicate a major role of FcγII-R and its downstream signaling cascade in the phagocytosis of quartz particles in AM as well as in the associated generation and release of inflammatory mediators.

scholarly journals A simplified methodology: pH sensing using an in situ fabricated Ir electrode under neutral conditions

2021 ◽  
Author(s):  
Yuqi Chen ◽  
Xiuting Li ◽  
Danlei Li ◽  
Christopher Batchelor-McAuley ◽  
Richard G. Compton
Keyword(s):  
Ph Sensor ◽  
Iridium Oxide ◽  
Ph Sensitive ◽  
Ph Sensing ◽  
Ph Dependency ◽  
Acidic Conditions ◽  
Ph Range ◽  
Neutral Conditions ◽  
Electrochemical Fabrication

AbstractHerein, a simplified fabrication method for the producing of a pH-sensitive iridium electrode is developed. The in situ electrochemical fabrication of an iridium oxide film is optimized and shown to be achievable under neutral conditions rather than the acidic conditions hitherto employed. The formation of a pH sensitive Ir(III/IV) hydrous film is confirmed via XPS. The amperometric pH-sensing properties of this electrochemically generated material were investigated using square wave voltammetry. In the pH range 2–13, the iridium oxide redox signal has a pH dependency of 86.1 ± 1.1 mV per pH unit for midpoint potentials with uncertainties being ± 0.01–0.05 pH. Finally, the newly developed pH sensor was used to measure the pH of a natural water sample with excellent results as compared to a conventional glass pH probe.

Crucial polarity regulators in axon specification

2012 ◽  
Vol 53 ◽  
pp. 55-68 ◽  
Author(s):  
Giovanna Lalli
Keyword(s):  
Nervous System ◽  
Hippocampal Neurons ◽  
Molecular Mechanisms ◽  
Membrane Traffic ◽  
Small Gtpases ◽  
Cell Polarization ◽  
Microtubule Cytoskeleton ◽  
Morphological Asymmetry ◽  
Neuronal Polarization

Cell polarization is critical for the correct functioning of many cell types, creating functional and morphological asymmetry in response to intrinsic and extrinsic cues. Neurons are a classical example of polarized cells, as they usually extend one long axon and short branched dendrites. The formation of such distinct cellular compartments (also known as neuronal polarization) ensures the proper development and physiology of the nervous system and is controlled by a complex set of signalling pathways able to integrate multiple polarity cues. Because polarization is at the basis of neuronal development, investigating the mechanisms responsible for this process is fundamental not only to understand how the nervous system develops, but also to devise therapeutic strategies for neuroregeneration. The last two decades have seen remarkable progress in understanding the molecular mechanisms responsible for mammalian neuronal polarization, primarily using cultures of rodent hippocampal neurons. More recent efforts have started to explore the role of such mechanisms in vivo. It has become clear that neuronal polarization relies on signalling networks and feedback mechanisms co-ordinating the actin and microtubule cytoskeleton and membrane traffic. The present chapter will highlight the role of key molecules involved in neuronal polarization, such as regulators of the actin/microtubule cytoskeleton and membrane traffic, polarity complexes and small GTPases.

scholarly journals MiR-376a inhibits non-small cell lung cancer cell progression by regulating Rab1A

2019 ◽  
Author(s):  
Zheng-Hao Cao ◽  
Jing-Liang Cheng ◽  
Xian-Zhao Zheng ◽  
Qing-Qing Lv ◽  
Jin-Xin Ma ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Cell Proliferation ◽  
Small Cell Lung Cancer ◽  
Cell Lung Cancer ◽  
Crucial Role ◽  
Molecular Mechanisms ◽  
Small Cell ◽  
Migration And Invasion ◽  
Small Cell Lung

Abstract Post transcriptional gene regulation of microRNA-376a (miR-376a) plays a crucial role for tumorigenesis and cancer development. However, the potential role of miR-367a in non-small cell lung cancer (NSCLC) remains unclear. In this study, we investigated the crucial role of miR-376a in NSCLC by analyzing miR-376a expression as well as its target genes. Through overexpression strategies, we uncovered the molecular mechanisms underlying miR-376a-mediated tumorigenesis. Quantitative real-time PCR analysis demonstrated miR-376a levels to be significantly decreased in NSCLC cells compared with non-tumorigenic counterparts. Interestingly, miR-376a overexpression potentially repressed NSCLC cell proliferation, migration, and invasion, but increased apoptosis in A549 cells. Using bioinformatic approaches, we predicted that miR-376a targets Rab1A, and further luciferase fusion assay demonstrated Rab1A was a direct target of miR-376a and miR-376a inhibited cell proliferation by regulating the mRNA and protein levels of Rab1A in NSCLC cells. Overall, our findings uncover the miR-376a could suppress NSCLC cells progression via directly targeting Rab1A.

Role of Rho-GTPases and their regulatory proteins in glomerular podocyte function

2013 ◽  
Vol 91 (10) ◽  
pp. 773-782 ◽  
Author(s):  
Flaviana Mouawad ◽  
Harmony Tsui ◽  
Tomoko Takano
Keyword(s):  
Rho Gtpases ◽  
Molecular Mechanisms ◽  
Complex Structure ◽  
Critical Role ◽  
Normal Function ◽  
Small Gtpases ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Cellular Functions

Podocytes play a critical role in maintaining glomerular permselectivity. It has been long recognized that their intricate actin-based structures are tightly associated with their normal function; however, the precise mechanisms by which podocytes form and maintain their complex structure had been poorly understood until the intensive investigations on podocyte biology began in 1998, triggered by the breakthrough discovery of nephrin. This review summarizes the recent discoveries of the molecular mechanisms by which the actin cytoskeleton is regulated in podocytes. A particular focus will be on the role of the Rho-family of small GTPases, represented by RhoA, Rac1, and Cdc42. Rho-GTPases are known for their versatile cellular functions, most importantly for the actin regulatory roles. We will also discuss the potential roles of the 3 groups of proteins known to regulate Rho-GTPases, namely GTPase-activating proteins, guanine nucleotide exchange factors, and guanine nucleotide dissociation inhibitors.

scholarly journals Crucial Role of Bysl in Mammalian Preimplantation Development as an Integral Factor for 40S Ribosome Biogenesis

2007 ◽  
Vol 27 (6) ◽  
pp. 2202-2214 ◽  
Author(s):  
Kenjiro Adachi ◽  
Chie Soeta-Saneyoshi ◽  
Hiroshi Sagara ◽  
Yoichiro Iwakura
Keyword(s):  
Crucial Role ◽  
Ribosome Biogenesis ◽  
Molecular Mechanisms ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Ribosomal Subunit ◽  
Preimplantation Development ◽  
Dominant Negative ◽  
Blastocyst Formation

ABSTRACT Blastocyst formation during mammalian preimplantation development is a unique developmental process that involves lineage segregation between the inner cell mass and the trophectoderm. To elucidate the molecular mechanisms underlying blastocyst formation, we have functionally screened a subset of preimplantation embryo-associated transcripts by using small interfering RNA (siRNA) and identified Bysl (bystin-like) as an essential gene for this process. The development of embryos injected with Bysl siRNA was arrested just prior to blastocyst formation, resulting in a defect in trophectoderm differentiation. Silencing of Bysl by using an episomal short hairpin RNA expression vector inhibited proliferation of embryonic stem cells. Exogenously expressed Bysl tagged with a fluorescent protein was concentrated in the nucleolus with a diffuse nucleoplasmic distribution. Furthermore, the loss of Bysl function by using RNA interference or dominant negative mutants caused defects in 40S ribosomal subunit biogenesis. These findings provide evidence for a crucial role of Bysl as an integral factor for ribosome biogenesis and suggest a critical dependence of blastocyst formation on active translation machinery.

scholarly journals Crucial Role of Juvenile Hormone Receptor Components Methoprene-Tolerant and Taiman in Sexual Maturation of Adult Male Desert Locusts

Biomolecules ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 244
Author(s):  
Michiel Holtof ◽  
Joachim Van Lommel ◽  
Marijke Gijbels ◽  
Elfie Dekempeneer ◽  
Bart Nicolai ◽  
...  
Keyword(s):  
Juvenile Hormone ◽  
Adult Male ◽  
Sexual Maturation ◽  
Crucial Role ◽  
Molecular Mechanisms ◽  
Relative Weight ◽  
Reproductive Physiology ◽  
Corpora Allata ◽  
Reproductive Capacity

Currently (2020), Africa and Asia are experiencing the worst desert locust (Schistocerca gregaria) plague in decades. Exceptionally high rainfall in different regions caused favorable environmental conditions for very successful reproduction and population growth. To better understand the molecular mechanisms responsible for this remarkable reproductive capacity, as well as to fill existing knowledge gaps regarding the regulation of male reproductive physiology, we investigated the role of methoprene-tolerant (Scg-Met) and Taiman (Scg-Tai), responsible for transducing the juvenile hormone (JH) signal, in adult male locusts. We demonstrated that knockdown of these components by RNA interference strongly inhibits male sexual maturation, severely disrupting reproduction. This was evidenced by the inability to show mating behavior, the absence of a yellow-colored cuticle, the reduction of relative testes weight, and the drastically reduced phenylacetonitrile (PAN) pheromone levels of the treated males. We also observed a reduced relative weight, as well as relative protein content, of the male accessory glands in Scg-Met knockdown locusts. Interestingly, in these animals the size of the corpora allata (CA), the endocrine glands where JH is synthesized, was significantly increased, as well as the transcript level of JH acid methyltransferase (JHAMT), a rate-limiting enzyme in the JH biosynthesis pathway. Moreover, other endocrine pathways appeared to be affected by the knockdown, as evidenced by changes in the expression levels of the insulin-related peptide and two neuroparsins in the fat body. Our results demonstrate that JH signaling pathway components play a crucial role in male reproductive physiology, illustrating their potential as molecular targets for pest control.

scholarly journals SWI/SNF senses carbon starvation with a pH-sensitive low complexity sequence

2021 ◽  
Author(s):  
J. Ignacio Gutiérrez ◽  
Gregory P. Brittingham ◽  
Yonca B. Karadeniz ◽  
Kathleen D. Tran ◽  
Arnob Dutta ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Ph Sensor ◽  
Transcriptional Response ◽  
Low Complexity ◽  
Carbon Starvation ◽  
Ph Sensing ◽  
Ph Changes ◽  
Transcriptional Reprogramming ◽  
Biophysical Mechanism

AbstractIt is increasingly appreciated that intracellular pH changes are important biological signals. This motivates the elucidation of molecular mechanisms of pH-sensing. We determined that a nucleocytoplasmic pH oscillation was required for the transcriptional response to carbon starvation in S. cerevisiae. The SWI/SNF chromatin remodeling complex is a key mediator of this transcriptional response. We found that a glutamine-rich low complexity sequence (QLC) in the SNF5 subunit of this complex, and histidines within this sequence, were required for efficient transcriptional reprogramming during carbon starvation. Furthermore, the SNF5 QLC mediated pH-dependent recruitment of SWI/SNF to a model promoter in vitro. Simulations showed that protonation of histidines within the SNF5 QLC lead to conformational expansion, providing a potential biophysical mechanism for regulation of these interactions. Together, our results indicate that that pH changes are a second messenger for transcriptional reprogramming during carbon starvation, and that the SNF5 QLC acts as a pH-sensor.

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