scholarly journals Stochastic activation and bistability in a Rab GTPase regulatory network

2020 ◽  
Vol 117 (12) ◽  
pp. 6540-6549
Author(s):  
Urban Bezeljak ◽  
Hrushikesh Loya ◽  
Beata Kaczmarek ◽  
Timothy E. Saunders ◽  
Martin Loose
Keyword(s):  
Regulatory Network ◽  
Regulatory Networks ◽  
Membrane Surface ◽  
Activity Patterns ◽  
Small Gtpases ◽  
Signaling Networks ◽  
Rab Gtpase ◽  
Endomembrane System ◽  
In Vitro Reconstitution

The eukaryotic endomembrane system is controlled by small GTPases of the Rab family, which are activated at defined times and locations in a switch-like manner. While this switch is well understood for an individual protein, how regulatory networks produce intracellular activity patterns is currently not known. Here, we combine in vitro reconstitution experiments with computational modeling to study a minimal Rab5 activation network. We find that the molecular interactions in this system give rise to a positive feedback and bistable collective switching of Rab5. Furthermore, we find that switching near the critical point is intrinsically stochastic and provide evidence that controlling the inactive population of Rab5 on the membrane can shape the network response. Notably, we demonstrate that collective switching can spread on the membrane surface as a traveling wave of Rab5 activation. Together, our findings reveal how biochemical signaling networks control vesicle trafficking pathways and how their nonequilibrium properties define the spatiotemporal organization of the cell.

scholarly journals Stochastic activation and bistability in a Rab GTPase regulatory network

2019 ◽  
Author(s):  
Urban Bezeljak ◽  
Hrushikesh Loya ◽  
Beata Kaczmarek ◽  
Timothy E. Saunders ◽  
Martin Loose
Keyword(s):  
Positive Feedback ◽  
Regulatory Network ◽  
Signaling Networks ◽  
Rab Gtpase ◽  
Rab Gtpases ◽  
Nucleotide Exchange ◽  
Intracellular Traffic ◽  
Bistable Switching ◽  
In Vitro Reconstitution

AbstractRab GTPases are the central regulators of intracellular traffic. Their function relies on a conformational change triggered by nucleotide exchange and hydrolysis. While this switch is well understood for an individual protein, how Rab GTPases collectively transition between states to generate a biochemical signal in space and time is unclear. Here, we combine in vitro reconstitution experiments with theoretical modeling to study a minimal Rab5 activation network. We find that positive feedback in this network gives rise to bistable switching of Rab5 activation and provide evidence that controlling the inactive population of Rab5 on the membrane can shape the network response. Together, our findings reveal new insights into the non-equilibrium properties and general principles of biochemical signaling networks underlying the spatiotemporal organization of the cell.

scholarly journals Improved reconstitution of yeast vacuole fusion with physiological SNARE concentrations reveals an asymmetric Rab(GTP) requirement

2016 ◽  
Vol 27 (16) ◽  
pp. 2590-2597 ◽  
Author(s):  
Michael Zick ◽  
William Wickner
Keyword(s):  
Acyl Chain ◽  
Fatty Acyl ◽  
Fatty Acyl Chain ◽  
Rab Gtpase ◽  
Lower Phase ◽  
Yeast Vacuole ◽  
Vacuole Fusion ◽  
In Vitro Reconstitution

In vitro reconstitution of homotypic yeast vacuole fusion from purified components enables detailed study of membrane fusion mechanisms. Current reconstitutions have yet to faithfully replicate the fusion process in at least three respects: 1) The density of SNARE proteins required for fusion in vitro is substantially higher than on the organelle. 2) Substantial lysis accompanies reconstituted fusion. 3) The Rab GTPase Ypt7 is essential in vivo but often dispensable in vitro. Here we report that changes in fatty acyl chain composition dramatically lower the density of SNAREs that are required for fusion. By providing more physiological lipids with a lower phase transition temperature, we achieved efficient fusion with SNARE concentrations as low as on the native organelle. Although fused proteoliposomes became unstable at elevated SNARE concentrations, releasing their content after fusion had occurred, reconstituted proteoliposomes with substantially reduced SNARE concentrations fused without concomitant lysis. The Rab GTPase Ypt7 is essential on both membranes for proteoliposome fusion to occur at these SNARE concentrations. Strikingly, it was only critical for Ypt7 to be GTP loaded on membranes bearing the R-SNARE Nyv1, whereas the bound nucleotide of Ypt7 was irrelevant on membranes bearing the Q-SNAREs Vam3 and Vti1.

scholarly journals Identification of the TF-miRNA-mRNA Co-regulatory Networks Involved in Sepsis

2021 ◽  
Author(s):  
Xiaoqian Luo ◽  
Weina Lu ◽  
Jianfeng Zhao ◽  
Jun Hu ◽  
Enjiang Chen ◽  
...  
Keyword(s):  
Expression Analysis ◽  
Regulatory Network ◽  
Regulatory Networks ◽  
Mirna Target ◽  
Target Genes ◽  
Medical Condition ◽  
Differentially Expressed ◽  
Biological Targets ◽  
Differentially Expressed Mirnas

Abstract BackgroundSepsis is a life-threatening medical condition caused by a dysregulated host response to infection. Recent studies have found that the expression of miRNAs is associated with the pathogenesis of sepsis and septic shock. Our study aimed to reveal which miRNAs may be involved in the dysregulated immune response in sepsis and how these miRNAs interact with transcription factors (TFs) using a computational approach with in vitro validation studies. MethodsTo determine the network of TFs, miRNAs and target genes involved in sepsis, GEO datasets GSE94717 and GSE131761 were used to identify differentially expressed miRNAs and DEGs. TargetScan and miRWalk databases were used to predict biological targets that overlap with the identified DEGs of differentially expressed miRNAs. The TransmiR database was used to predict the differential miRNA TFs that overlap with the identified DEGs. The TF-miRNA-mRNA network was constructed and visualized. Finally, qRT-PCR was used to verify the expression of TFs and miRNA in HUVECs. ResultBetween the healthy and sepsis groups, there were 146 upregulated and 98 downregulated DEGs in the GSE131761 dataset, and there were 1 upregulated and 183 downregulated DEMs in the GSE94717 dataset. A regulatory network of the TF-miRNA-target genes was established. According to the experimental results, RUNX3 was found to be downregulated while MAPK14 was upregulated, which corroborates the result of the computational expression analysis. In a HUVECs model, miR-19b-1-5p and miR-5009-5p were found to be significantly downregulated. Other TFs and miRNAs did not correlate with our bioinformatics expression analysis. ConclusionWe constructed a TF-miRNA-target gene regulatory network and identified potential treatment targets RUNX3, MAPK14, miR-19b-1-5p and miR-5009-5p. This information provides an initial basis for understanding the complex sepsis regulatory mechanisms.

scholarly journals Regulation of Arf activation occurs via distinct mechanisms at early and late Golgi compartments

2017 ◽  
Vol 28 (25) ◽  
pp. 3660-3671 ◽  
Author(s):  
Margaret A. Gustafson ◽  
J. Christopher Fromme
Keyword(s):  
Membrane Surface ◽  
Critical Mass ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Decision Makers ◽  
Regulatory Mechanisms ◽  
Clear Understanding ◽  
Membrane Surfaces ◽  
Arf Gtpases

At the Golgi complex, the biosynthetic sorting center of the cell, the Arf GTPases are responsible for coordinating vesicle formation. The Arf-GEFs activate Arf GTPases and are therefore the key molecular decision-makers for trafficking from the Golgi. In Saccharomyces cerevisiae, three conserved Arf-GEFs function at the Golgi: Sec7, Gea1, and Gea2. Our group has described the regulation of Sec7, the trans-Golgi Arf-GEF, through autoinhibition, positive feedback, dimerization, and interactions with a suite of small GTPases. However, we lack a clear understanding of the regulation of the early Golgi Arf-GEFs Gea1 and Gea2. Here we demonstrate that Gea1 and Gea2 prefer neutral over anionic membrane surfaces in vitro, consistent with their localization to the early Golgi. We illustrate a requirement for a critical mass of either Gea1 or Gea2 for cell growth under stress conditions. We show that the C-terminal domains of Gea1 and Gea2 toggle roles in the cytosol and at the membrane surface, preventing membrane binding in the absence of a recruiting interaction but promoting maximum catalytic activity once recruited. We also identify the small GTPase Ypt1 as a recruiter for Gea1 and Gea2. Our findings illuminate core regulatory mechanisms unique to the early Golgi Arf-GEFs.

scholarly journals Gene regulatory network (GRN) embedded agents connect cellular decision making to human pluripotent stem cell derived germ layer-like pattern formation

2020 ◽  
Author(s):  
Himanshu Kaul ◽  
Nicolas Werschler ◽  
Mukul Tewary ◽  
Andrew Hagner ◽  
Joel Ostblom ◽  
...  
Keyword(s):  
Stem Cell ◽  
Gene Regulatory Network ◽  
Regulatory Network ◽  
Regulatory Networks ◽  
Pluripotent Stem Cell ◽  
Network Activity ◽  
Germ Layer ◽  
Human Pluripotent Stem Cell ◽  
Gene Regulatory

ABSTRACTThe emergence of germ layers in embryos during gastrulation is a key developmental milestone. How morphogenetic signals engage the regulatory networks responsible for early embryonic tissue patterning is incompletely understood. To understand this, we developed a gene regulatory network (GRN) model of human pluripotent stem cell (hPSC) lineage commitment and embedded it into ‘cellular’ agents that respond to a dynamic signalling microenvironment. We found that cellular pattern order, composition, and dynamics were predictably manipulable based on the GRN wiring. We showed that feedback between OCT4, and BMP and WNT pathways created a dynamic OCT4 front that mediates the spatiotemporal evolution of developmental patterns. Translocation of this radial front can be predictively disrupted in vitro to control germ-layer pattern composition. This work links the emergence of multicellular patterns to regulatory network activity in individual hPSCs. We anticipate our approach will help to understand how GRN structure regulates organogenesis in different contexts.

In vitro Charakterisierung des Rab-GTPase-aktivierenden Proteins TBC1D1

2011 ◽  
Vol 6 (S 01) ◽  
Author(s):  
F Neumann ◽  
M Gompert ◽  
HW Klein ◽  
J Dokas ◽  
A Chadt ◽  
...  
Keyword(s):  
Rab Gtpase

scholarly journals Multi-omic regulatory networks capture downstream effects of kinase inhibition in Mycobacterium tuberculosis

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Albert T. Young ◽  
Xavier Carette ◽  
Michaela Helmel ◽  
Hanno Steen ◽  
Robert N. Husson ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Mycobacterium Tuberculosis ◽  
Regulatory Network ◽  
Regulatory Networks ◽  
Protein Interaction Data ◽  
Kinase Inhibition ◽  
Protein Protein Interaction ◽  
Downstream Effects ◽  
Regulate Cell Growth ◽  
Regulatory Effects

AbstractThe ability of Mycobacterium tuberculosis (Mtb) to adapt to diverse stresses in its host environment is crucial for pathogenesis. Two essential Mtb serine/threonine protein kinases, PknA and PknB, regulate cell growth in response to environmental stimuli, but little is known about their downstream effects. By combining RNA-Seq data, following treatment with either an inhibitor of both PknA and PknB or an inactive control, with publicly available ChIP-Seq and protein–protein interaction data for transcription factors, we show that the Mtb transcription factor (TF) regulatory network propagates the effects of kinase inhibition and leads to widespread changes in regulatory programs involved in cell wall integrity, stress response, and energy production, among others. We also observe that changes in TF regulatory activity correlate with kinase-specific phosphorylation of those TFs. In addition to characterizing the downstream regulatory effects of PknA/PknB inhibition, this demonstrates the need for regulatory network approaches that can incorporate signal-driven transcription factor modifications.

scholarly journals Macropinocytosis requires Gal-3 in a subset of patient-derived glioblastoma stem cells

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Laetitia Seguin ◽  
Soline Odouard ◽  
Francesca Corlazzoli ◽  
Sarah Al Haddad ◽  
Laurine Moindrot ◽  
...  
Keyword(s):  
Stem Cells ◽  
Cell Survival ◽  
Small Gtpases ◽  
Molecular Signature ◽  
Carbohydrate Binding ◽  
Pancreatic Cancers ◽  
Galectin 3 ◽  
Pharmacologic Inhibition

AbstractRecently, we involved the carbohydrate-binding protein Galectin-3 (Gal-3) as a druggable target for KRAS-mutant-addicted lung and pancreatic cancers. Here, using glioblastoma patient-derived stem cells (GSCs), we identify and characterize a subset of Gal-3high glioblastoma (GBM) tumors mainly within the mesenchymal subtype that are addicted to Gal-3-mediated macropinocytosis. Using both genetic and pharmacologic inhibition of Gal-3, we showed a significant decrease of GSC macropinocytosis activity, cell survival and invasion, in vitro and in vivo. Mechanistically, we demonstrate that Gal-3 binds to RAB10, a member of the RAS superfamily of small GTPases, and β1 integrin, which are both required for macropinocytosis activity and cell survival. Finally, by defining a Gal-3/macropinocytosis molecular signature, we could predict sensitivity to this dependency pathway and provide proof-of-principle for innovative therapeutic strategies to exploit this Achilles’ heel for a significant and unique subset of GBM patients.

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