Visualisering av protein-proteininteraktion i nukleära och cytoplasmiska fraktioner av Co-immunoprecipitation och<em> In Situ</em> Proximity Ligation Assay
Summary
Protein-protein interactions can occur in both the nucleus and the cytoplasm of a cell. To investigate these interactions, traditional co-immunoprecipitation and modern proximity ligation assay are applied. In this study, we compare these two methods to visualize the distribution of NF90-RBM3 interactions in the nucleus and the cytoplasm.
Abstract
Protein-protein interactions are involved in thousands of cellular processes and occur in distinct spatial context. Traditionally, co-immunoprecipitation is a popular technique to detect protein-protein interactions. Subsequent Western blot analysis is the most common method to visualize co-immunoprecipitated proteins. Recently, the proximity ligation assay has become a powerful tool to visualize protein-protein interactions in situ and provides the possibility to quantify protein-protein interactions by this method. Similar to conventional immunocytochemistry, the proximity ligation assay technique is also based on the accessibility of primary antibodies to the antigens, but in contrast, proximity ligation assay detects protein-protein interactions with a unique technique involving rolling-circle PCR, while conventional immunocytochemistry only shows co-localization of proteins.
Nuclear factor 90 (NF90) and RNA-binding motif protein 3 (RBM3) have been previously demonstrated as interacting partners. They are predominantly localized in the nucleus, but also migrate into the cytoplasm and regulate signaling pathways in the cytoplasmic compartment. Here, we compared NF90-RBM3 interaction in both the nucleus and the cytoplasm by co-immunoprecipitation and proximity ligation assay. In addition, we discussed the advantages and limitations of these two techniques in visualizing protein-protein interactions in respect to spatial distribution and the properties of protein-protein interactions.
Introduction
Nukleär faktor 90 (NF90) är en multi-isoform protein med många funktioner, inklusive svar på virusinfektion, reglering av interleukin-2 efter transkription och reglering av miRNA biogenes 1-3. RBM3 är ett RNA-bindande protein, involverat i översättning och miRNA biogenes och kan induceras av olika stress inklusive hypotermi och hypoxi 4-6. Nyligen fann vi NF90 och RBM3 i ett proteinkomplex 7. Interaktionen mellan NF90 och RBM3 är viktigt att modulera proteinkinas RNA liknande endoplasmatiska retiklet kinas (PERK) aktivitet i ovikt protein svar 7. Både NF90 och RBM3 ligger främst i kärnan men en liten del av NF90 och RBM3 shuttle in i cytoplasman och binda det till varandra för specifika funktioner, till exempel för att reglera PERK aktivitet. Därför är det viktigt att visualisera fördelningen av NF90-RBM3 interaktioner i subcellulär avdelning, vilket kan tyda påderas olika roller i respektive fack.
Decennier sedan, jäst två hybrid (Y2H) utvecklats för att detektera växelverkan mellan två proteiner 8. Emellertid, på grund av artificiell konstruktion av sammansmälta proteiner, har falska positiva resultat begränsat tillämpningen av denna metod. Under en lång tid, co-immunoprecipitation var huvud teknik för att analysera protein-proteininteraktioner, särskilt i endogena förhållanden 9. För att analysera sam-immunoprecipiterade proteinkomplexet, är Western blot den lämpligaste tekniken, medan masspektrometri används när super känslighet och noggrannhet önskas. Under de senaste åren har närhet ligering analys utvecklats som en ny metod för att detektera protein-proteininteraktioner i både celler och vävnader in situ 10,11.
Här, vi jämförde mest populära co-immunoprecipitation metod och relativt ny närhet ligering analysmetod fånga NF90-RBM3 interaktion i subcellulära fraktioner. Vi diskuterade också de fördelar och begränsningar av båda teknikerna.
Protocol
Representative Results
Discussion
Det finns flera fördelar liksom brister för båda metoderna. Som en relativt ny teknik, är en uppenbar fördel av närheten ligation assay möjligheten att belysa protein-proteininteraktioner vid encelliga nivå i stället för en sats av heterogena celler. Bilder med hög magnitud och upplösning (t.ex. genom konfokalmikroskop) ger möjlighet för kvantifiering genom att räkna enskilda fluorescerande fläckar. I motsats härtill den konventionella kombinationen av co-immunoprecipitation tekniken med Wester…
Disclosures
The authors have nothing to disclose.
Acknowledgements
This study was supported by the Swiss National Science Foundation (SNSF, 31003A_163305).
Materials
| Dulbecco's Modified Eagle’s Medium (DMEM) | Sigma | D6429 | High glucose 4500 mg/L |
| Fetal bovine serum (FBS) | Gibco, Thermo Fisher Scientific | 10270106 | |
| Penicillin-Streptomycin (PenStrep) | BioConcept | 4-01F00-H | |
| NE-PER Nuclear and Cytoplasmic Extraction Reagents | Thermo Fisher Scientific | 78833 | |
| 1,4-Dithiothreitol (DTT) | Carl Roth | 6908.3 | |
| Dynabeads Protein G | Novex, Thermo Fisher Scientific | 10003D | |
| DRBP76 (NF90/NF110) antibody | BD Transduction Laboratories | 612154 | use 1:1000 for WB and 1:100 for ICC/PLA |
| RBM3 antibody | ProteinTech | 14363-1-AP | use 1:1000 for WB and 1:100 for ICC/PLA |
| Lamin A/C antibody | Cell Signaling Technology | #2032 | use 1:1000 for WB |
| anti-GAPDH antibody | Abcam | ab8245 | use 1:1000 for WB |
| normal rabbit IgG | Santa Cruz | sc-2027 | |
| anti-rabbit IgG, HRP-lined secodary antiboy | Cell Signaling Technology | #7074 | use 1:5000 for WB |
| anti-mouse HRP secondary antibody | Carl Roth | 4759.1 | use 1:5000 for WB |
| Clarity Western ECL Blotting Substrate | Bio-Rad | #1705060 | |
| NuPAGE Novex 4-12% Bis-Tris Gel | Novex, Thermo Fisher Scientific | NP0321BOX | |
| NuPAGE LDS Sample Buffer (4x) | Novex, Thermo Fisher Scientific | NP0007 | |
| 1,4-Dithiothreitol (DTT) | CarlRoth | 6908.1 | |
| NuPAGE MES SDS Running Buffer (20x) | Novex, Thermo Fisher Scientific | NP0002 | |
| NuPAGE Transfer Buffer (20x) | Novex, Thermo Fisher Scientific | NP00061 | |
| Amersham Hypond P 0.2 PVDF membrane | GE Healthcare Life Sciences | 10600021 | |
| Super RX X-ray film | Fujifilm | 4741029230 | |
| Poly-D-Lysine 8 Well Culture Slide | Corning BioCoat | 354632 | |
| Paraformaldehyde (PFA) | Sigma | P6148 | |
| Normal goat serum (NGS) | Gibco, Thermo Fisher Scientific | PCN5000 | |
| Goat anti-mouse IgG (H+L Antibody), Alexa Fluor 488 conjugate | Thermo Fisher Scientific | A-11001 | |
| Goat anti-rabbit IgG (H+L Antibody), Alexa Fluor 568 conjugate | Thermo Fisher Scientific | A-11011 | |
| 4′, 6-Diamidin-2-phenylindol (DAPI) | Sigma | D9542 | |
| Duolink PLA probe Anti-mouse PLUS | Sigma | DUO92001 | |
| Duolink PLA probe Anti-rabbit MINUS | Sigma | DUO92005 | |
| Duolink Detection Reagents Red | Sigma | DUO92008 | |
| Duolink Wash Buffers Fluorescence | Sigma | DUO82049 | |
| Duolink Mounting Medium with DAPI | Sigma | DUO82040 | |
| Mowiol 4-88 | Sigma | 81381 | |
| Microscope | Olympus | AX-70 | |
| CCD camera | SPOT | Insight 2MP Firewire | |
| X-ray film | Fujifilm | Super RX | |
| Film processing machine | Fujifilm | FPM-100A |
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