scholarly journals Constrained actin dynamics emerges from variable compositions of actin regulatory protein complexes

2019 ◽  
Author(s):  
Ulrich Dobramysl ◽  
Iris K Jarsch ◽  
Hanae Shimo ◽  
Yoshiko Inoue ◽  
Benjamin Richier ◽  
...  
Keyword(s):  
Functional Outcomes ◽  
Dynamic Behaviour ◽  
Protein Complexes ◽  
Regulatory Protein ◽  
Regulatory Proteins ◽  
Actin Dynamics ◽  
Free System ◽  
Stochastic Fluctuations ◽  
A Cell ◽  
Dynamic Morphology

AbstractAssemblies of actin and its regulators underlie the dynamic morphology of all eukaryotic cells. To begin to understand how diverse regulatory proteins work together to generate actin-rich structures we tracked the assembly of actin regulators and their relative proportions in a cell-free system that generates filopodia-like structures (FLS). We found that heterogeneous mixtures of regulators could give rise to morphologically similar structures and that the FLS actin bundles exhibited simple dynamic behaviour of growth and shrinkage. To explain these observations, we combined experiment with theory, and found that stochastic fluctuations between redundant actin regulatory subcomplexes can account for the actin dynamics. Comparing the localizations of a variety of endogenous actin regulators in Drosophila embryos and distributions of filopodia lengths yielded similar conclusions of heterogenous actin regulatory complexes and filopodia lengths governed by a stochastic growth process. Our results explain how weakly-associating assemblies of regulatory proteins can produce robust functional outcomes.

scholarly journals Structural and functional insights into transmembrane AMPA receptor regulatory protein complexes

2019 ◽  
Vol 151 (12) ◽  
pp. 1347-1356 ◽  
Author(s):  
Edward C. Twomey ◽  
Maria V. Yelshanskaya ◽  
Alexander I. Sobolevsky
Keyword(s):  
Protein Complexes ◽  
Regulatory Protein ◽  
Regulatory Proteins ◽  
Specific Gene ◽  
Modular Architecture ◽  
Auxiliary Subunits ◽  
Functional Studies ◽  
Excitatory Neurotransmission ◽  
Synaptic Complexes ◽  
The Brain

Fast excitatory neurotransmission is mediated by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtype of ionotropic glutamate receptor (AMPAR). AMPARs initiate depolarization of the postsynaptic neuron by allowing cations to enter through their ion channel pores in response to binding of the neurotransmitter glutamate. AMPAR function is dramatically affected by auxiliary subunits, which are regulatory proteins that form various complexes with AMPARs throughout the brain. The most well-studied auxiliary subunits are the transmembrane AMPAR regulatory proteins (TARPs), which alter the assembly, trafficking, localization, kinetics, and pharmacology of AMPARs. Recent structural and functional studies of TARPs and the TARP-fold germ cell-specific gene 1-like (GSG1L) subunit have provided important glimpses into how auxiliary subunits regulate the function of synaptic complexes. In this review, we put these recent structures in the context of new functional findings in order to gain insight into the determinants of AMPAR regulation by TARPs. We thus reveal why TARPs display a broad range of effects despite their conserved modular architecture.

Regulation of Rho protein binding to membranes by rhoGDI: inhibition of releasing activity by physiological ionic conditions

1999 ◽  
Vol 77 (1) ◽  
pp. 59-69 ◽  
Author(s):  
Diane Bilodeau ◽  
Sylvie Lamy ◽  
Richard R Desrosiers ◽  
Denis Gingras ◽  
Richard Béliveau
Keyword(s):  
Ionic Strength ◽  
Brush Border ◽  
Rat Kidney ◽  
Regulatory Protein ◽  
Rho Proteins ◽  
Glutathione S Transferase ◽  
Free System ◽  
Brush Border Membranes ◽  
A Cell ◽  
Membrane Bound

The Rho GDP dissociation inhibitor (GDI) is an ubiquitously expressed regulatory protein involved in the cycling of Rho proteins between membrane-bound and soluble forms. Here, we characterized the Rho solubilization activity of a glutathione S-transferase (GST) - GDI fusion protein in a cell-free system derived from rat kidney. Addition of GST-GDI to kidney brush border membranes resulted in the specific release of Cdc42 and RhoA from the membranes, while RhoB and Ras were not extracted. The release of Cdc42 and RhoA by GST-GDI was dose dependent and saturable with about 50% of both RhoA and Cdc42 extracted. The unextracted Rho proteins were tightly bound to membranes and could not be solubilized by repeated GST-GDI treatment. These results demonstrated that kidney brush border membranes contained two populations of RhoA and Cdc42. Furthermore, the GST-GDI solubilizing activity on membrane-bound Cdc42 and RhoA was abolished at physiological conditions of salt and temperature in all tissues examined. When using bead-immobilized GST-GDI, KCl did not reduced the binding of Rho proteins. However, washing brush border membranes with KCl prior treatment by GST-GDI inhibited the extraction of Rho proteins. Taken together, these results suggest that the binding of GDI to membrane-bound Cdc42 and RhoA occurs easily under physiological ionic strength conditions, but a complementary factor is required to extract these proteins from membranes. These observations suggest that the shuttling activity of GDI upon Rho proteins could be normally downregulated under physiological conditions.Key words: rhoGDI, rho proteins, ionic strength, kidney.

scholarly journals Stochastic combinations of actin regulatory proteins are sufficient to drive filopodia formation

2021 ◽  
Vol 220 (4) ◽  
Author(s):  
Ulrich Dobramysl ◽  
Iris Katharina Jarsch ◽  
Yoshiko Inoue ◽  
Hanae Shimo ◽  
Benjamin Richier ◽  
...  
Keyword(s):  
Regulatory Protein ◽  
Regulatory Proteins ◽  
Eukaryotic Cells ◽  
In Vitro System ◽  
Multiple Components ◽  
Dynamic Morphology ◽  
Actin Regulatory Proteins ◽  
Drosophila Embryos

Assemblies of actin and its regulators underlie the dynamic morphology of all eukaryotic cells. To understand how actin regulatory proteins work together to generate actin-rich structures such as filopodia, we analyzed the localization of diverse actin regulators within filopodia in Drosophila embryos and in a complementary in vitro system of filopodia-like structures (FLSs). We found that the composition of the regulatory protein complex where actin is incorporated (the filopodial tip complex) is remarkably heterogeneous both in vivo and in vitro. Our data reveal that different pairs of proteins correlate with each other and with actin bundle length, suggesting the presence of functional subcomplexes. This is consistent with a theoretical framework where three or more redundant subcomplexes join the tip complex stochastically, with any two being sufficient to drive filopodia formation. We provide an explanation for the observed heterogeneity and suggest that a mechanism based on multiple components allows stereotypical filopodial dynamics to arise from diverse upstream signaling pathways.

Combination of ribosome and phage display for fast selection of high affinity VHH antibody fragments

2019 ◽  
pp. 27-33
Author(s):  
YuE Kravchenko ◽  
SV Ivanov ◽  
DS Kravchenko ◽  
EI Frolova ◽  
SP Chumakov
Keyword(s):  
Phage Display ◽  
Selection Procedure ◽  
Free System ◽  
Phage Displays ◽  
High Affinity ◽  
Binding Domains ◽  
A Cell ◽  
Vhh Antibodies ◽  
Efficiency Of Selection ◽  
Selection Of

Selection of antibodies using phage display involves the preliminary cloning of the repertoire of sequences encoding antigen-binding domains into phagemid, which is considered the bottleneck of the method, limiting the resulting diversity of libraries and leading to the loss of poorly represented variants before the start of the selection procedure. Selection in cell-free conditions using a ribosomal display is devoid from this drawback, however is highly sensitive to PCR artifacts and the RNase contamination. The aim of the study was to test the efficiency of a combination of both methods, including pre-selection in a cell-free system to enrich the source library, followed by cloning and final selection using phage display. This approach may eliminate the shortcomings of each method and increase the efficiency of selection. For selection, alpaca VHH antibody sequences suitable for building an immune library were used due to the lack of VL domains. Analysis of immune libraries from the genes of the VH3, VHH3 and VH4 families showed that the VHH antibodies share in the VH3 and VH4 gene groups is insignificant, and selection from the combined library is less effective than from the VHH3 family of sequences. We found that the combination of ribosomal and phage displays leads to a higher enrichment of high-affinity fragments and avoids the loss of the original diversity during cloning. The combined method allowed us to obtain a greater number of different high-affinity sequences, and all the tested VHH fragments were able to specifically recognize the target, including the total protein extracts of cell cultures.

scholarly journals Effect of detergents on sterol synthesis in a cell-free system of yeast

1982 ◽  
Vol 23 (6) ◽  
pp. 803-810
Author(s):  
S Hata ◽  
T Nishino ◽  
N Ariga ◽  
H Katsuki
Keyword(s):  
Sterol Synthesis ◽  
Free System ◽  
Cell Free System ◽  
A Cell

scholarly journals Reconstitution of Endosomal Proteolysis in a Cell-free System

1989 ◽  
Vol 264 (10) ◽  
pp. 5392-5399
Author(s):  
L S Mayorga ◽  
R Diaz ◽  
P D Stahl
Keyword(s):  
Free System ◽  
Cell Free System ◽  
A Cell

scholarly journals Novel Method for Quantifying AhR-Ligand Binding Affinities Using Microscale Thermophoresis

Biosensors ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 60
Author(s):  
Anne Stinn ◽  
Jens Furkert ◽  
Stefan H. E. Kaufmann ◽  
Pedro Moura-Alves ◽  
Michael Kolbe
Keyword(s):  
Ligand Binding ◽  
Environmental Pollutants ◽  
Screening Strategy ◽  
Pharmacological Intervention ◽  
Binding Affinities ◽  
Free System ◽  
Microscale Thermophoresis ◽  
Aryl Hydrocarbon ◽  
Promising Target ◽  
A Cell

The aryl hydrocarbon receptor (AhR) is a highly conserved cellular sensor of a variety of environmental pollutants and dietary-, cell- and microbiota-derived metabolites with important roles in fundamental biological processes. Deregulation of the AhR pathway is implicated in several diseases, including autoimmune diseases and cancer, rendering AhR a promising target for drug development and host-directed therapy. The pharmacological intervention of AhR processes requires detailed information about the ligand binding properties to allow specific targeting of a particular signaling process without affecting the remaining. Here, we present a novel microscale thermophoresis-based approach to monitoring the binding of purified recombinant human AhR to its natural ligands in a cell-free system. This approach facilitates a precise identification and characterization of unknown AhR ligands and represents a screening strategy for the discovery of potential selective AhR modulators.

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