HEK-Blue™ hTLR8 Cells
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Cat.code:
hkb-htlr8
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ABOUT
NF-κB–SEAP reporter HEK293 cells expressing human TLR8
HEK-Blue™ hTLR8 cells were engineered from the human embryonic kidney HEK293 cell line to study the Toll-like receptor 8 (TLR8)-dependent NF-κB pathway. This important pattern recognition receptor (PRR) recognizes viral single-stranded RNA (ssRNA) structures and subsequently triggers NF-κB and IRF immune responses[1].
Description
HEK-Blue™ hTLR8 cells express the human TLR8 gene as well as an NF-κB/AP-1-inducible SEAP reporter gene. SEAP (secreted embryonic alkaline phosphatase) levels produced upon TLR8 stimulation can be readily determined by performing the assay in HEK-Blue™ Detection, a cell culture medium that allows for real-time detection of SEAP. Alternatively, SEAP activity may be monitored using QUANTI-Blue™, a SEAP detection reagent.
Due to the expression of hTLR8, HEK-Blue™ hTLR8 cells strongly and stably respond to TLR8-specific ligands (see figures). Interestingly, while HEK-Blue™ murine (m)TLR8 cells do not respond to the TLR8 agonist ssRNA40, HEK-Blue™ hTLR8 cells respond to this ligand (see figures). Thus, findings regarding mouse TLR8 are not transposable to its human counterpart [1,2].
HEK-Blue™ hTLR8 cells do not respond to TLR7-specific ligands, since HEK293 cells do not express endogenous TLR7 (see figures). However, as they express endogenous levels of TLR3, TLR5, and NOD1 [in-house data], HEK-Blue™ hTLR8 cells may respond to their cognate ligands such as Poly(I:C), flagellin, or Tri-DAP (see figure).
As TLR8 activates both the NF-κB and IRF signaling pathways, InvivoGen also offers HEK-Dual™ hTLR7 cells; a cell line expressing a dual reporter system comprising an NF-κB-inducible SEAP and an IRF-inducible-Lucia luciferase (learn more here).
Of note, HEK293 cells express endogenous levels of various PRRs, including TLR3 and TLR5. Therefore, they might respond to their cognate ligands (see figures).
Key Features
- Verified expression of human (h)TLR8
- Strong and stable response to TLR8-specific ligands
- Distinct monitoring of NF-κB by assessing the SEAP activities
Applications
- Defining the distinct role of TLR8 in the NF-κB-dependent pathway
- Comparing human and murine TLR8-responses using the HEK-Blue™ mTLR8 cell line
- Screening for novel TLR8-specific agonists or inhibitors in comparison with their parental cell line HEK-Blue™ Null1
References:
1. Heil F. et al., 2004. Species-specific recognition of single-stranded RNA via Toll-like receptor 7 and 8. Science. 303:1526.
2. Eigenbrod T. & Dalpke A.H., 2015. Bacterial RNA: an underestimated stimulus for innate immune responses. J. Immunol. 195:411.
3. Georg P. & Sander L.E., 2019. Innate sensors that regulate vaccine responses. Curr. Op. Immunol. 59:31.
Disclaimer: These cells are for internal research use only and are covered by a Limited Use License (See Terms and Conditions). Additional rights may be available.
SPECIFICATIONS
Specifications
TLR8
Human
TLR8 activation cellular assays
Complete DMEM (see TDS)
Verified using Plasmotest™
Each lot is functionally tested and validated.
CONTENTS
Contents
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Product:HEK-Blue™ hTLR8 Cells
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Cat code:hkb-htlr8
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Quantity:3-7 x 10^6 cells
- 1 ml Blasticidin (10 mg/ml)
- 1 ml Zeocin® (100 mg/ml)
- 1 ml Normocin™ (50 mg/ml)
- 1 pouch of HEK-Blue™ Detection (cell culture medium for real-time detection of SEAP)
Shipping & Storage
- Shipping method: Dry ice
- Liquid nitrogen vapor
Storage:
Details
Toll-Like Receptor 8
In humans, four Toll-Like Receptor (TLR) family members TLR3, TLR7, TLR8, and TLR9, mainly found in the endosome, are specialized in sensing viral-derived components. TLR7 and TLR8 recognize single-stranded (ss)RNA structures, such as viral ssRNA, miRNA, and various synthetic agonists [1]. Despite their similarities in PAMP (pathogen-associated molecular pattern) recognition, structure, and signaling partners, they highly differ in expression profiles and signaling responses, with TLR7 being more involved in the antiviral immune response and TLR8 mastering the production of proinflammatory cytokines [2]. TLR7 is mainly found in plasmacytoid dendritic cells (pDCs) and B cells, whereas TLR8 is highly expressed in monocytes, monocyte-derived DCs (mDCs), and macrophages [3].
TLR8 signaling
Upon viral infection, TLR8 translocates from the endoplasmic reticulum via the Golgi into the endosomes. Subsequently, it undergoes proteolytic cleavage in order to facilitate dimer rearrangement [1,3]. While TLR7 dimerizes upon ligand binding, TLR8, which exists as an unliganded inactive dimer, performs structural reorganization after ligand recognition [4]. Once activated, TLR8 recruits the adaptor protein MyD88 to trigger IRF, AP-1, and NF-kB responses via TRAF6 (TNF receptor-associated factor 6) [1,3]. Depending on the stimulus and cell type, TLR8-mediated signaling induces Th1-type cytokine (IL-12) production [5].
TLR8 therapeutic targeting
The involvement of nucleic acid-sensing mechanisms in the immune response against infections and other diseases makes them interesting targets for drug design [5]. TLR7/8 agonists are currently been tested as vaccine adjuvants and immunomodulatory therapeutics. They are extensively studied in the context of viral infection (e.g. SARS-CoV-2, Influenza, HIV), autoimmune (e.g. asthma, Lupus), and autoinflammatory diseases (e.g. cancer) [1-5]. Understanding the fundamental differences between these two related receptors could potentially be harnessed to discover novel drugs and improve vaccine efficacy/safety [5].
References:
1. Martínez-Espinoza I & Guerrero-Plata A. 2022. The Relevance of TLR8 in Viral Infections. Pathogens. 11(2):134.
2. Salvi V, et al., 2021. SARS-CoV-2-associated ssRNAs activate inflammation and immunity via TLR7/8. JCI Insight.;6(18):e150542.
3. Georg P. & Sander L.E., 2019. Innate sensors that regulate vaccine responses. Curr. Op. Immunol. 59:31.
4. Asami J, Shimizu T. 2021. Structural and functional understanding of the toll-like receptors. Protein Sci. (4):761-772.
5. de Marcken M, et al., 2019. TLR7 and TLR8 activate distinct pathways in monocytes during RNA virus infection. Sci Signal.;12(605):eaaw1347.
DOCUMENTS
Documents
Technical Data Sheet
Safety Data Sheet
Validation Data Sheet
Certificate of analysis
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