C5AR1 Knockout THP-1 Cell Line

The C5AR1 Knockout THP-1 Cell Line is a CRISPR/Cas9-edited human monocytic leukemia cell line with targeted disruption of the C5AR1 gene encoding the complement anaphylatoxin C5a receptor (CD88). This G protein-coupled receptor mediates chemotaxis, degranulation, and pro-inflammatory responses in myeloid cells. The CRISPR/Cas9-mediated gene disruption eliminates functional C5AR1 expression, providing a defined loss-of-function model for dissecting C5a-driven signaling without endogenous receptor interference.

THP-1 cells are a widely used human monocytic leukemia line originally isolated from a patient with acute monocytic leukemia (AML M5). They serve as a classic model for investigating monocyte and macrophage biology, including differentiation, immune response, and inflammatory processes. Upon phorbol ester treatment, THP-1 cells differentiate into macrophage-like cells, broadening experimental utility. Their endogenous C5AR1 expression and robust responsiveness to C5a make this knockout line particularly suitable for comparative studies of complement signaling in myeloid contexts.

C5AR1 functions as the primary receptor for the anaphylatoxin C5a, activating heterotrimeric G proteins G??i and G??q. Downstream, phospholipase C-?? generates IP3 and diacylglycerol, triggering intracellular calcium mobilization and protein kinase C activation. C5AR1 couples to the PI3K/AKT pathway and MAPK cascades, including ERK1/2 and p38 MAPK, which converge on transcription factors NF-??B and AP-1 to drive production of pro-inflammatory cytokines such as IL-6, IL-8, and TNF-??. Additionally, C5AR1 promotes actin cytoskeleton rearrangement through Rho family GTPases, facilitating chemotaxis and degranulation. The receptor interacts with ??-arrestin-1 for desensitization and internalization, and forms functional complexes with CD11b/CD18 integrin to modulate leukocyte adhesion and migration. Upstream, C5a is generated by complement C5 convertases, and receptor activation is influenced by inflammatory mediators including LPS, TNF-??, and IL-6.

In the THP-1 context, knockout of C5AR1 eliminates C5a-induced calcium mobilization, chemotactic migration, and secretion of inflammatory cytokines, confirming its essential role. This engineered cell line enables precise dissection of C5AR1-dependent and -independent pathways in monocytic cells. It is particularly valuable for exploring how complement anaphylatoxins intersect with innate immune signals, for validating the specificity of pharmacological C5a receptor antagonists, and for generating isogenic comparisons in studies of sepsis, acute lung injury, rheumatoid arthritis, and ischemia-reperfusion injury. The amenability of THP-1 cells to genetic manipulation and functional assays further supports high-throughput screening of compounds targeting complement-driven inflammation.

Key research applications include mechanistic studies of C5a-mediated signaling in monocytes and macrophages, inflammatory disease modeling, and drug discovery efforts aimed at C5AR1 blockade. The cell line is compatible with a variety of experimental techniques, such as Western blotting to confirm protein loss, flow cytometry for CD88 expression quantification, calcium mobilization assays, chemotaxis assays, and cytokine ELISAs for IL-6 and IL-8. Transcriptomic analyses via RNA-seq or RT-qPCR can reveal changes in downstream gene networks, while NF-??B reporter assays and phagocytosis assays offer functional readouts. In cancer immunology, the role of C5a in tumor-associated macrophage polarization can be explored using this model. For further information or to discuss custom applications, please contact Ascent Research.