Name: investigating the function of coronin a in the early starvation response of dictyostelium discoideum by aggregation assays
Uploaded: 2016-06-18T15:00:00.000+00:00
Duration: 7 min 48 s
Description: Watch this Scientific Journal Video about Investigating the Function of Coronin A in the Early Starvation Response of Dictyostelium discoideum by Aggregation Assays at JoVE.com

We thank the Dictyostelium Stock Center for strains and reagents. This study was financed by grants from the Swiss National Science Foundation and the Canton of Basel.

<ol><li> Osservare la risposta di inedia precoce di Dictyostelium discoideum mediante microscopia time-lapse. <ol><li> Crescere le cellule DH1.10 o cellule Corà -carente in un flacone contenente Erlenmayer HL-5 di media (per 1 L: 5 g proteoso peptone, 5 g thiotone E peptone, 10 g di glucosio, 5 g di estratto di lievito, 0,35 g di Na 2 HPO 4 * 7H 2 O, 0,35 g KH 2 PO 4, 0,05 g diidrostreptomicina-solfato, pH 6,6) a 22 ° C in un incubatore agitazione con una rotazione di 160 rpm. Mantenere le cellule ad una densità tra 0,01 x 10 6 cellule / ml e 2 x 10 6 cellule / ml. </li><li> Esaminare l&#39;aggregazione delle cellule, per la raccolta di log-fase di crescita le cellule DH1.10 21 o cellule Cora -carente 10 generata in background DH1.10, coltivate in agitazione cultura con HL-5 di media a 22 ° C. Per fare ciò, adottare le opportune quantità di cellule (di solito tra 10 e 50 ml), centrifugare per 3 minuti a 400 xg e lavare le cellule due volte in BSS (10 mM NaCl, 10 mM KCl, 2.5 mM CaCl 2, pH 6,5). </li><li> Contare le cellule utilizzando un emocitometro. Successivamente, le cellule piastra ad una densità di (5, 10, 20, o 40) x 10 4 cellule / cm 2 in una piastra da 24 pozzetti. Consentire loro di aderire per 1 ora a 22 ° C in BSS. </li><li> Visualizza aggregazione mediante microscopia time-lapse come descritto in precedenza 10, prendendo immagini ogni 135 secondi. utilizzando un imaging cellulare dal vivo istituito dotata di obiettivo 5X e una fotocamera del dispositivo ad accoppiamento di carica elettrone-moltiplicando automatizzato dal software appropriato (vedi Materiali Tavolo). </li></ol></li><li> cAMP pulsare delle cellule discoideum Dictyostelium durante il digiuno. <ol><li> Esaminare l&#39;effetto degli impulsi di cAMP applicati esternamente sullo sviluppo delle cellule DH1.10 21 o cellule 10 DH1.10 CORA -carente, raccogliendo le cellule. Per fare ciò, adottare le opportune quantità di cellule (di solito tra 10 e 50 ml), centrifugare per 3 minuti a 400 xg e lavare due volte in BSS. </li><li> coucellule NT utilizzando un emocitometro e risospendere le cellule ad una densità di 1 x 10 7 cellule / ml in BSS. Agitare le culture (160 rpm) a 22 ° C per 2 ore prima di applicare impulsi. Aggiungere impulsi cAMP utilizzando una pompa peristaltica temporizzata. Programmare la pompa per erogare un impulso 5 sec ogni 6,5 min di 15 ml di 50 nM cAMP (concentrazione finale) in un periodo di 5 ore. </li><li> Contare le cellule utilizzando un emocitometro. Successivamente, le cellule piastra ad una densità di (5, 10, 20, o 40) x 10 4 cellule / cm 2 in una piastra da 24 pozzetti. Lasciare aderire per 1 ora a BSS. </li><li> Visualizza aggregazione dopo 16 ore a 22 ° C mediante microscopia in campo chiaro con obiettivo 5X. </li></ol></li><li> Induzione di Dictyostelium discoideum sviluppo attraverso l&#39;esposizione a mezzo condizionato. <ol><li> Preparare fresco mezzo condizionato come descritto 22. Raccogliere le cellule DH1.10 log-fase 21 o celle 10 DH1.10 Cora -carente, di tremare cultoUres con HL-5 di media a 22 ° C con una pipetta, centrifugare per 3 minuti a 400 xg e lavare le cellule tre volte in PBM (0,02 M di fosfato di potassio, 10 mM CaCl 2, e 1 mm MgCl 2, pH 6.1). </li><li> Contare le cellule utilizzando un emocitometro, risospendere questi in PBM ad una densità di 1 x 10 7 cellule / ml e agitare per 20 ore a 110 rpm / 22 ° C. </li><li> Raccogliere mezzo condizionato dopo centrifugazione a 400 g per 3 min e chiarire per centrifugazione a 8.000 xg per 15 min a 4 ° C. </li><li> Filtro condizionata mezzo attraverso un filtro da 0,45 micron (vedi Materiali Tavolo) e diluire in triplice PBM. </li><li> Contare le cellule utilizzando un emocitometro e la piastra ad una densità di (5, 10, 20, o 40) x 10 4 cellule / cm 2 in una piastra da 24 pozzetti. Consentire loro di aderire per 1 ora a 22 ° C. </li><li> Scambio supernatante delle cellule con il mezzo precedentemente preparato condizionata. </li><li> Visualizza l&#39;aggregazione di unopo 16 ore al microscopio in campo chiaro utilizzando un obiettivo 5X. </li></ol></li></ol>

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No conflicts of interest declared.

Le proteine ​​Coronin si trovano nella maggior parte dei taxa del clade eucariotica. Dictyostelium discoideum Coronin A, l&#39;omologo di Coronin mammiferi 1, è coinvolto nella risposta di inedia in anticipo, dal momento che Coronin Un deficit di cellule non sono in grado di formare centri di aggregazione durante l&#39;inizio dello sviluppo ciclo 10. Per essere in grado di valutare quantitativamente e con precisione il ritardo di sviluppo tra i ceppi, un set-up microscopio imaging cellulare dal ...

La famiglia Coronin delle proteine ​​è altamente conservata in tutta eucarioti. Queste proteine ​​sono caratterizzati dalla presenza di un triptofano-aspartato amino-terminale (WD) ripetere contenente regione seguita da una regione unica collegata a un dominio coiled-coil carbossi-terminale 13,14 (figura 1). Coronins sono stati implicati in una varietà di funzioni cellulari, tra cui la regolamentazione del citoscheletro e trasduzione del segnale 12. Nei mammiferi, fino a sei brevi molecole Coronin (Coronin 1-6) e un &#39;tandem&#39; Coronin 7, possono essere co-espressi 12,15. Coronin 1 è il membro della famiglia più ampiamente studiato, e ha dimostrato di essere coinvolto in distruzione degli agenti patogeni, la sopravvivenza delle cellule T e la segnalazione neuronale. Come, esattamente, Coronin 1 svolge tali attività rimane poco chiaro. Mentre Coronin 1 è stato mostrato per regolare Ca 2+ e cAMP-dipendente di segnalazione così come F-actina citoscheletro modulazione 16-18, il potenziale co-expression di un massimo di 7 membri della famiglia nei mammiferi ha reso difficile per studiare la funzione molecolare di coronins in questi sistemi, a causa di potenziali esuberi. A differenza di organismi dei mammiferi, il più basso eucariote Dictyostelium discoideum esprime solo due membri della famiglia Coronin (Coronin A, la ortologo di mammiferi Coronin 1 e Coronin B, la ortologo di Coronin mammiferi 7) con funzioni apparentemente non ridondanti 15,19,20. Questo fatto rende Dictyostelium discoideum un modello potente per studiare la funzione di coronins. Per studiare il ruolo di Coronin A in Dictyostelium discoideum, abbiamo indotto il ciclo di sviluppo per fame in piastre di coltura tissutale contenente tampone equilibrata soluzione salina (BSS) utilizzando sia le cellule di tipo selvatico o cellule prive Coronin A 10. Abbiamo scoperto che le cellule prive Coronin A erano in grado di formare aggregati multicellulari su fame. Per una valutazione quantitativa accurata di questa fenotipol&#39;imaging cellulare dal vivo automatizzato descritto in questo protocollo è uno strumento di vitale importanza. Il difetto nella inizio della risposta di inedia nelle prime cellule mancanti Coronin A può essere salvato fornendo impulsi di cAMP, suggerendo che Coronin A agisce a monte della cascata cAMP. L&#39;applicazione esogena di impulsi cAMP per simulare l&#39;apertura di sviluppo è stato utilizzato da diversi laboratori in passato 8,9. Tuttavia, questa procedura è anche noto per essere fortemente dipendente densità cellulari e temporizzazione. Pertanto, il protocollo qui descritto mira a ridurre questi variabilità per garantire un elevato grado di riproducibilità. Nel loro insieme, le tecniche utilizzate in questi studi forniscono strumenti robusti per indagare funzioni delle proteine ​​durante le prime fasi del ciclo di sviluppo di Dictyostelium discoideum e hanno il potenziale per identificare a monte così come effettori a valle di Coronin Una funzione.

<table><tbody><tr><td>HL-5 media (for 1 L: 5 g proteose peptone, 5 g thiotone E peptone, 10 g glucose, 5 g yeast extract, 0.35 g Na&lt;sub&gt;2&lt;/sub&gt;HPO&lt;sub&gt;4&lt;/sub&gt;*2H&lt;sub&gt;2&lt;/sub&gt;O, 0.35 g KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;, 0.05 g dihydrostreptomycin-sulfate, pH 6.6)</td><td></td><td></td><td></td></tr><tr><td>Proteose peptone</td><td>BD Bioscience</td><td>211693</td><td></td></tr><tr><td>Thiotone E peptone</td><td>BD Bioscience</td><td>211684</td><td></td></tr><tr><td>Yeast extract</td><td>BD Bioscience</td><td>212750</td><td></td></tr><tr><td>Glucose</td><td>AppliChem</td><td>A3666</td><td></td></tr><tr><td>Na&lt;sub&gt;2&lt;/sub&gt;HPO&lt;sub&gt;4&lt;/sub&gt;*2H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Fluka</td><td>71643</td><td></td></tr><tr><td>KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;</td><td>AppliChem</td><td>A1043</td><td></td></tr><tr><td>dihydrostreptomycin-sulfate</td><td>Sigma-Aldrich</td><td>D1954000</td><td></td></tr><tr><td>PBM (0.02 M potassium phosphate, 10 &amp;mu;M CaCl&lt;sub&gt;2&lt;/sub&gt;, and l mM MgCl&lt;sub&gt;2&lt;/sub&gt;, pH 6.1)</td><td></td><td></td><td>self made</td></tr><tr><td>BSS (10 mM NaCl, 10 mM KCl, 2.5 mM CaCl&lt;sub&gt;2&lt;/sub&gt;, pH 6.5)</td><td></td><td></td><td>self made</td></tr><tr><td>0.45-&amp;mu;m Filtropure S filter</td><td>Sarstedt</td><td>83.1826</td><td></td></tr><tr><td>Falcon 24-well Tissue culture plate</td><td>Fisher Scientific</td><td>08-772-1H</td><td></td></tr><tr><td>Cellobserver microscope</td><td>Zeiss</td><td></td><td>custom built</td></tr><tr><td>AxioVision software</td><td>Zeiss</td><td></td><td></td></tr><tr><td>IPC Microprocessor&amp;ndash;controlled dispensing pump</td><td>ISMATEC</td><td>ISM 931</td><td></td></tr><tr><td>Axiovert 135M microscope</td><td>Zeiss</td><td>491237-0001-000</td><td></td></tr><tr><td>Incubation Shaker</td><td>Inforst HT Minitron</td><td></td><td></td></tr></tbody></table>

investigating the function of coronin a in the early starvation response of dictyostelium discoideum by aggregation assays

Dictyostelium discoideum un&#39;ameba si trovano nel terreno, si nutrono di batteri. Quando fonti di cibo diventano scarse, secernono fattori di avviare un programma di sviluppo multicellulare, durante il quale le singole cellule chemiotassi verso i centri di aggregazione 1-4. Questo processo dipende dal rilascio di adenosina monofosfato ciclico (cAMP) 5. cAMP è prodotto in onde attraverso l&#39;azione concertata di ciclasi e fosfodiesterasi, e si lega al G recettori accoppiati alla proteina cAMP 6,7. Un test ampiamente utilizzato per analizzare i meccanismi coinvolti nel ciclo di sviluppo del eucariote Dictyostelium discoideum inferiore si basa sull&#39;osservazione di aggregazione delle cellule in condizioni sommerse 8,9. Questo protocollo descrive l&#39;analisi del ruolo di Coronin A nel ciclo di sviluppo per fame in piastre tessuto-coltura sommersa in soluzione salina bilanciata (BSS) 10. Coronin A è un membro del pr ampiamente conservatafamiglia otein di coronins che sono stati implicati in una vasta gamma di attività 11,12. Dictyostelium cellule prive Coronin A sono in grado di formare aggregati multicellulari, e questo difetto può essere salvato fornendo impulsi di cAMP, suggerendo che Coronin A agisce a monte della cAMP cascata 10. Le tecniche descritte in questi studi forniscono strumenti robusti per indagare funzioni delle proteine ​​durante le fasi iniziali del ciclo di sviluppo di Dictyostelium discoideum monte della cascata cAMP. Pertanto, utilizzando questo test aggregazione può consentire l&#39;ulteriore studio della Coronin Una funzione e far progredire la nostra comprensione della biologia Coronin.

Le cellule carenti di Coronin Uno spettacolo un difetto di sviluppo precoce (figura 2). In assenza di Coronin A cellule sono in grado di formare aggregati multicellulari, che è la fase iniziale durante il ciclo di sviluppo di Dictyostelium discoideum. Pertanto, Coronin A sembra giocare un ruolo durante la risposta di inedia precoce e / o segnalazione cAMP. Infatti, la mancanza di formazione degli aggregati multicellulare in assenza di Coronin A è accompagnato ...

Watch this Scientific Journal Video about Investigating the Function of Coronin A in the Early Starvation Response of Dictyostelium discoideum by Aggregation Assays at JoVE.com

Investigating the Function of Coronin A in the Early Starvation Response of Dictyostelium discoideum by Aggregation Assays

The social amoeba Dictyostelium discoideum undergoes a developmental transition into a multicellular organism when starved. The evolutionary conserved protein coronin A plays a crucial role in the initiation of development. Using aggregation assays as our main method, we aim to elucidate the role of coronin A in early development.

Indagare la funzione di Coronin A nel precoce fame di risposta<em&gt; Discoideum Dictyostelium</em&gt; Per aggregazione Dosaggi

Dictyostelium discoideum amoeba are found in soil, feeding on bacteria. When food sources become scarce, they secrete factors to initiate a multicellular ...

investigating-function-coronin-early-starvation-response

Research

JoVE Journal

Biology

Investigating the Function of Coronin A in the Early Starvation Response of Dictyostelium discoideum by Aggregation Assays

7.2K Views.  University of Basel. The social amoeba Dictyostelium discoideum undergoes a developmental transition into a multicellular organism when starved. The evolutionary conserved protein coronin A plays a crucial role in the initiation of development. Using aggregation assays as our main method, we aim to elucidate the role of coronin A in early development.

Video: Investigating the Function of Coronin A in the Early Starvation Response of Dictyostelium discoideum by Aggregation Assays

Genetic Engineering of Dictyostelium discoideum Cells Based on Selection and Growth on Bacteria

Dictyostelium discoideum is an intriguing model organism for the study of cell differentiation processes during development, cell signaling, and other important cellular biology questions. The technologies available to genetically manipulate Dictyostelium cells are well-developed. Transfections can be performed using different selectable markers and marker re-cycling, including homologous recombination and insertional mutagenesis. This is supported by a well-annotated genome. However, these approaches are optimized for axenic cell lines growing in liquid cultures and are difficult to apply to non-axenic wild-type cells, which feed only on bacteria. The mutations that are present in axenic strains disturb Ras signaling, causing excessive macropinocytosis required for feeding, and impair cell migration, which confounds the interpretation of signal transduction and chemotaxis experiments in those strains. Earlier attempts to genetically manipulate non-axenic cells have lacked efficiency and required complex experimental procedures. We have developed a simple transfection protocol that, for the first time, overcomes these limitations. Those series of large improvements to Dictyostelium molecular genetics allow wild-type cells to be manipulated as easily as standard laboratory strains. In addition to the advantages for studying uncorrupted signaling and motility processes, mutants that disrupt macropinocytosis-based growth can now be readily isolated. Furthermore, the entire transfection workflow is greatly accelerated, with recombinant cells that can be generated in days rather than weeks. Another advantage is that molecular genetics can further be performed with freshly isolated wild-type Dictyostelium samples from the environment. This can help to extend the scope of approaches used in these research areas.

Genetic Engineering of Dictyostelium discoideum Cells Based on Selection and Growth on Bacteria

Dictyostelium discoideum is a popular model organism to study complex cellular processes such as cell migration, endocytosis, and development. The utility of the organism is dependent on the feasibility of genetic manipulation. Here, we present methods to transfect Dictyostelium discoideum cells that overcome existing limitations of culturing cells in liquid media.

Ingegneria genetica di Dictyostelium discoideum cellule basata sulla selezione e crescita sui batteri

Dictyostelium discoideum is an intriguing model organism for the study of cell differentiation processes during development, cell signaling, and other ...

Ricerca

Genetica

Monitoring Protein Aggregation Kinetics In Vivo using Automated Inclusion Counting in Caenorhabditis elegans

Protein aggregation into insoluble inclusions is a hallmark of a variety of human diseases, many of which are age-related. The nematode Caenorhabditis elegans is a well-established model organism that has been widely used in the field to study protein aggregation and toxicity. Its optical transparency enables the direct visualization of protein aggregation by fluorescence microscopy. Moreover, the fast reproductive cycle and short lifespan make the nematode a suitable model to screen for genes and molecules that modulate this process.
However, the quantification of aggregate load in living animals is poorly standardized, typically performed by manual inclusion counting under a fluorescence dissection microscope at a single time point. This approach can result in high variability between observers and limits the understanding of the aggregation process. In contrast, amyloid-like protein aggregation in vitro is routinely monitored by thioflavin T fluorescence in a highly quantitative and time-resolved fashion.
Here, an analogous method is presented for the unbiased analysis of aggregation kinetics in living C. elegans, using a high-throughput confocal microscope combined with custom-made image analysis and data fitting. The applicability of this method is demonstrated by monitoring inclusion formation of a fluorescently labeled polyglutamine (polyQ) protein in the body wall muscle cells. The image analysis workflow allows the determination of the numbers of inclusions at different timepoints, which are fitted to a mathematical model based on independent nucleation events in individual muscle cells. The method described here may prove useful to assess the effects of proteostasis factors and potential therapeutics for protein aggregation diseases in a living animal in a robust and quantitative manner.

Monitoring Protein Aggregation Kinetics In Vivo using Automated Inclusion Counting in Caenorhabditis elegans

Here, a method is presented for the analysis of protein aggregation kinetics in the nematode Caenorhabditis elegans. Animals from an age-synchronized population are imaged at different time points, followed by semiautomated inclusion counting in CellProfiler and fitting to a mathematical model in AmyloFit.

Monitoraggio della cinetica di aggregazione proteica in vivo utilizzando il conteggio automatico dell'inclusione in Caenorhabditis elegans

Protein aggregation into insoluble inclusions is a hallmark of a variety of human diseases, many of which are age-related. The nematode Caenorhabditis ...

Biochimica

Imaging G-protein Coupled Receptor (GPCR)-mediated Signaling Events that Control Chemotaxis of Dictyostelium Discoideum

Many eukaryotic cells can detect gradients of chemical signals in their environments and migrate accordingly 1. This guided cell migration is referred as chemotaxis, which is essential for various cells to carry out their functions such as trafficking of immune cells and patterning of neuronal cells 2, 3. A large family of G-protein coupled receptors (GPCRs) detects variable small peptides, known as chemokines, to direct cell migration in vivo 4. The final goal of chemotaxis research is to understand how a GPCR machinery senses chemokine gradients and controls signaling events leading to chemotaxis. To this end, we use imaging techniques to monitor, in real time, spatiotemporal concentrations of chemoattractants, cell movement in a gradient of chemoattractant, GPCR mediated activation of heterotrimeric G-protein, and intracellular signaling events involved in chemotaxis of eukaryotic cells 5-8. The simple eukaryotic organism, Dictyostelium discoideum, displays chemotaxic behaviors that are similar to those of leukocytes, and D. discoideum is a key model system for studying eukaryotic chemotaxis. As free-living amoebae, D. discoideum cells divide in rich medium. Upon starvation, cells enter a developmental program in which they aggregate through cAMP-mediated chemotaxis to form multicullular structures. Many components involved in chemotaxis to cAMP have been identified in D. discoideum. The binding of cAMP to a GPCR (cAR1) induces dissociation of heterotrimeric G-proteins into G&gamma; and G&beta;&gamma; subunits 7, 9, 10. G&beta;&gamma; subunits activate Ras, which in turn activates PI3K, converting PIP2 into PIP3 on the cell membrane 11-13. PIP3 serve as binding sites for proteins with pleckstrin Homology (PH) domains, thus recruiting these proteins to the membrane 14, 15. Activation of cAR1 receptors also controls the membrane associations of PTEN, which dephosphorylates PIP3 to PIP2 16, 17. The molecular mechanisms are evolutionarily conserved in chemokine GPCR-mediated chemotaxis of human cells such as neutrophils 18. We present following methods for studying chemotaxis of D. discoideum cells. 1. Preparation of chemotactic component cells. 2. Imaging chemotaxis of cells in a cAMP gradient. 3. Monitoring a GPCR induced activation of heterotrimeric G-protein in single live cells. 4. Imaging chemoattractant-triggered dynamic PIP3 responses in single live cells in real time. Our developed imaging methods can be applied to study chemotaxis of human leukocytes.

Imaging G-protein Coupled Receptor GPCR-mediated Signaling Events that Control Chemotaxis of Dictyostelium Discoideum

Here, we describe detailed live cell imaging methods for investigating chemotaxis. We present fluorescence microscopic methods to monitor spatiotemporal dynamics of signaling events in migrating cells. Measurement of signaling events permits us to further understand how a GPCR-signaling network achieves gradient sensing of chemoattractants and controls directional migration of eukaryotic cells.

Receptor Imaging proteina G accoppiata (GPCR)-mediata eventi di segnalazione che chemiotassi di controllo di Dictyostelium discoideum</em

Many eukaryotic cells can detect gradients of chemical signals in their environments and migrate accordingly 1.  This guided cell migration is referred as ...

Biologia

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the function and regulation of protein folding was studied in vitro, in isolated tissue culture cells and in unicellular organisms. Recent studies have uncovered links between protein homeostasis (proteostasis), metabolism, development, aging, and temperature-sensing. These findings have led to the development of new tools for monitoring protein folding in the model metazoan organism Caenorhabditis elegans. In our laboratory, we combine behavioral assays, imaging and biochemical approaches using temperature-sensitive or naturally occurring metastable proteins as sensors of the folding environment to monitor protein misfolding. Behavioral assays that are associated with the misfolding of a specific protein provide a simple and powerful readout for protein folding, allowing for the fast screening of genes and conditions that modulate folding. Likewise, such misfolding can be associated with protein mislocalization in the cell. Monitoring protein localization can, therefore, highlight changes in cellular folding capacity occurring in different tissues, at various stages of development and in the face of changing conditions. Finally, using biochemical tools ex vivo, we can directly monitor protein stability and conformation. Thus, by combining behavioral assays, imaging and biochemical techniques, we are able to monitor protein misfolding at the resolution of the organism, the cell, and the protein, respectively.

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

To study the relationship between protein homeostasis, stress and aging, we monitored changes in protein folding by following protein dysfunction, protein localization in the cell and protein stability at the organismal, cellular and protein levels, using the genetically tractable metazoan Caenorhabditis elegans as a model system.

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the ...

Measuring Transcellular Interactions through Protein Aggregation in a Heterologous Cell System

Protein interactions at cellular interfaces dictate a multitude of biological outcomes ranging from tissue development and cancer progression to synapse formation and maintenance. Many of these fundamental interactions occur in trans and are typically induced by heterophilic or homophilic interactions between cells expressing membrane anchored binding pairs. Elucidating how disease relevant mutations disrupt these fundamental protein interactions can provide insight into a myriad of cell biology fields. Many protein-protein interaction assays do not typically disambiguate between cis and trans interactions, which potentially leads to an overestimation of the extent of binding that is occurring in vivo and involve labor intensive purification of protein and/or specialized monitoring equipment. Here, we present an optimized simple protocol that allows for the observation and quantification of only trans interactions without the need for lengthy protein purifications or specialized equipment. The HEK cell aggregation assay involves the mixing of two independent populations of HEK cells, each expressing membrane-bound cognate ligands. After a short incubation period, samples are imaged and the resulting aggregates are quantified.

Here, we present an optimized protocol to rapidly and semiquantitatively measure ligand-receptor interactions in trans in a heterologous cell system using fluorescence microscopy.

Misurare le interazioni transcellulari attraverso l'aggregazione proteica in un sistema di cellule eterologi

Protein interactions at cellular interfaces dictate a multitude of biological outcomes ranging from tissue development and cancer progression to synapse ...

Neuroscienze

Studying the Protein Quality Control System of D. discoideum Using Temperature-controlled Live Cell Imaging

The complex lifestyle of the social amoebae Dictyostelium discoideum makes it a valuable model for the study of various biological processes. Recently, we showed that D. discoideum is remarkably resilient to protein aggregation and can be used to gain insights into the cellular protein quality control system. However, the use of D. discoideum as a model system poses several challenges to microscopy-based experimental approaches, such as the high motility of the cells and their susceptibility to photo-toxicity. The latter proves to be especially challenging when studying protein homeostasis, as the phototoxic effects can induce a cellular stress response and thus alter to behavior of the protein quality control system. 
Temperature increase is a commonly used way to induce cellular stress. Here, we describe a temperature-controllable imaging protocol, which allows observing temperature-induced perturbations in D. discoideum. Moreover, when applied at normal growth temperature, this imaging protocol can also noticeably reduce photo-toxicity, thus allowing imaging with higher intensities. This can be particularly useful when imaging proteins with very low expression levels. Moreover, the high mobility of the cells often requires the acquisition of multiple fields of view to follow individual cells, and the number of fields needs to be balanced against the desired time interval and exposure time.

Studying the Protein Quality Control System of D. discoideum Using Temperature-controlled Live Cell Imaging

The social amoebae Dictyostelium discoideum has recently been established as a system to study protein misfolding and proteostasis. Here, we describe a new imaging-based methodology to study temperature-induced protein aggregation and the cellular stress response in D. discoideum.

Studiando la proteina del sistema di controllo di qualità di<em&gt; D. discoideum</em&gt; Uso Cellulare Imaging a temperatura controllata

The complex lifestyle of the social amoebae Dictyostelium discoideum makes it a valuable model for the study of various biological processes. Recently, we ...

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

Chemotaxis, or migration up a gradient of a chemoattractant, is the best understood mode of directed migration. Studies using social amoeba Dictyostelium discoideum revealed that a complex signal transduction network of parallel pathways amplifies the response to chemoattractants, and leads to biased actin polymerization and protrusion of a pseudopod in the direction of a gradient. In contrast, molecular mechanisms driving other types of directed migration, for example, due to exposure to shear flow or electric fields, are not known. Many regulators of chemotaxis exhibit localization at the leading or lagging edge of a migrating cell, as well as show transient changes in localization or activation following global stimulation with a chemoattractant. To understand the molecular mechanisms of other types of directed migration we developed a method that allows examination of cellular response to acute mechanical stimulation based on brief (2 - 5 s) exposure to shear flow. This stimulation can be delivered in a channel while imaging cells expressing fluorescently-labeled biosensors to examine individual cell behavior. Additionally, cell population can be stimulated in a plate, lysed, and immunoblotted using antibodies that recognize active versions of proteins of interest. By combining both assays, one can examine a wide array of molecules activated by changes in subcellular localization and/or phosphorylation. Using this method we determined that acute mechanical stimulation triggers activation of the chemotactic signal transduction and actin cytoskeleton networks. The ability to examine cellular responses to acute mechanical stimulation is important for understanding the initiating events necessary for shear flow-induced motility. This approach also provides a tool for studying the chemotactic signal transduction network without the confounding influence of the chemoattractant receptor.

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

Here we describe methods for assessing cellular response to acute mechanical stimulation. In the microscopy-based assay, we examine localization of fluorescently-labeled biosensors following brief stimulation with shear flow. We also test activation of various proteins of interest in response to acute mechanical stimulation biochemically.

Valutazione della risposta di Dictyostelium discoideum alla stimolazione meccanica acuta

Chemotaxis, or migration up a gradient of a chemoattractant, is the best understood mode of directed migration. Studies using social amoeba Dictyostelium ...

Methods to Study Changes in Inherent Protein Aggregation with Age in Caenorhabditis elegans

In the last decades, the prevalence of neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD), has grown. These age-associated disorders are characterized by the appearance of protein aggregates with fibrillary structure in the brains of these patients. Exactly why normally soluble proteins undergo an aggregation process remains poorly understood. The discovery that protein aggregation is not limited to disease processes and instead part of the normal aging process enables the study of the molecular and cellular mechanisms that regulate protein aggregation, without using ectopically expressed human disease-associated proteins. Here we describe methodologies to examine inherent protein aggregation in Caenorhabditis elegans through complementary approaches. First, we examine how to grow large numbers of age-synchronized C. elegans to obtain aged animals and we present the biochemical procedures to isolate highly-insoluble-large aggregates. In combination with a targeted genetic knockdown, it is possible to dissect the role of a gene of interest in promoting or preventing age-dependent protein aggregation by using either a comprehensive analysis with quantitative mass spectrometry or a candidate-based analysis with antibodies. These findings are then confirmed by in vivo analysis with transgenic animals expressing fluorescent-tagged aggregation-prone proteins. These methods should help clarify why certain proteins are prone to aggregate with age and ultimately how to keep these proteins fully functional.

Methods to Study Changes in Inherent Protein Aggregation with Age in Caenorhabditis elegans

The goal of the method presented here is to explore protein aggregation during normal aging in the model organism C. elegans. The protocol represents a powerful tool to study the highly insoluble large aggregates that form with age and to determine how changes in proteostasis impact protein aggregation.

Metodi di studio variazioni inerenti l'aggregazione proteica con l'età in Caenorhabditis elegans

In the last decades, the prevalence of neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD), has grown. These ...

High-throughput Measurement of Dictyostelium discoideum Macropinocytosis by Flow Cytometry

Large-scale non-specific fluid uptake by macropinocytosis is important for the proliferation of certain cancer cells, antigen sampling, host cell invasion and the spread of neurodegenerative diseases. The commonly used laboratory strains of the amoeba Dictyostelium discoideum have extremely high fluid uptake rates when grown in nutrient medium, over 90% of which is due to macropinocytosis. In addition, many of the known core components of mammalian macropinocytosis are also present, making it an excellent model system for studying macropinocytosis. Here, the standard technique to measure internalized fluid using fluorescent dextran as a label is adapted to a 96-well plate format, with the samples analyzed by flow cytometry using a high-throughput sampling (HTS) attachment.
Cells are fed non-quenchable fluorescent dextran for a pre-determined length of time, washed by immersion in ice-cold buffer and detached using 5 mM sodium azide, which also stops exocytosis. Cells in each well are then analyzed by flow cytometry. The method can also be adapted to measure membrane uptake and phagocytosis of fluorescent beads or bacteria.
This method was designed to allow measurement of fluid uptake by Dictyostelium in a high-throughput, labor and resource efficient manner. It allows simultaneous comparison of multiple strains (e.g. knockout mutants of a gene) and conditions (e.g. cells in different media or treated with different concentrations of inhibitor) in parallel and simplifies time-courses.

High-throughput Measurement of Dictyostelium discoideum Macropinocytosis by Flow Cytometry

Macropinocytosis, large-scale non-specific fluid uptake, is important in many areas of clinical biology including immunology, infection, cancer, and neurodegenerative diseases. Here, existing techniques have been adapted to allow high-throughput, single-cell resolution measurement of macropinocytosis in the macropinocytosis model organism Dictyostelium discoideum using flow cytometry.

Misurazione di alto-rendimento di Dictyostelium discoideum Macropinocitosi tramite flusso Cytometry

Large-scale non-specific fluid uptake by macropinocytosis is important for the proliferation of certain cancer cells, antigen sampling, host cell invasion ...

Detection of Protein Aggregation using Fluorescence Correlation Spectroscopy

Protein aggregation is a hallmark of neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and so on. To detect and analyze soluble or diffuse protein oligomers or aggregates, fluorescence correlation spectroscopy (FCS), which can detect the diffusion speed and brightness of a single particle with a single molecule sensitivity, has been used. However, the proper procedure and know-how for protein aggregation detection have not been widely shared. Here, we show a standard procedure of FCS measurement for diffusion properties of aggregation-prone proteins in cell lysate and live cells: ALS-associated 25 kDa carboxyl-terminal fragment of TAR DNA/RNA-binding protein 43 kDa (TDP25) and superoxide dismutase 1 (SOD1). The representative results show that a part of aggregates of green fluorescent protein (GFP)-tagged TDP25 was slightly included in the soluble fraction of murine neuroblastoma Neuro2a cell lysate. Moreover, GFP-tagged SOD1 carrying ALS-associated mutation shows a slower diffusion in live cells. Accordingly, we here introduce the procedure to detect the protein aggregation via its diffusion property using FCS.

We here introduce a procedure to measure protein oligomers and aggregation in cell lysate and live cells using fluorescence correlation spectroscopy.

Rilevamento dell'aggregazione proteica mediante spettroscopia di correlazione a fluorescenza

Protein aggregation is a hallmark of neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's ...

Indagare la funzione di Coronin A nel precoce fame di risposta

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Capitoli in questo video

Ingegneria genetica di Dictyostelium discoideum cellule basata sulla selezione e crescita sui batteri

Monitoraggio della cinetica di aggregazione proteica in vivo utilizzando il conteggio automatico dell'inclusione in Caenorhabditis elegans

Receptor Imaging proteina G accoppiata (GPCR)-mediata eventi di segnalazione che chemiotassi di controllo di Dictyostelium discoideum

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

Misurare le interazioni transcellulari attraverso l'aggregazione proteica in un sistema di cellule eterologi

Studiando la proteina del sistema di controllo di qualità di

Valutazione della risposta di Dictyostelium discoideum alla stimolazione meccanica acuta

Metodi di studio variazioni inerenti l'aggregazione proteica con l'età in Caenorhabditis elegans

Misurazione di alto-rendimento di Dictyostelium discoideum Macropinocitosi tramite flusso Cytometry

Rilevamento dell'aggregazione proteica mediante spettroscopia di correlazione a fluorescenza