KDELR3 Knockout HAP1 Polyclonal Cells are a CRISPR/Cas9-edited polyclonal knockout cell population derived from the near-haploid HAP1 cell line, designed for loss-of-function studies of the KDELR3 gene. This gene-edited pool provides a genetically heterogeneous model with disrupted KDELR3 expression, enabling investigation of ER protein retrieval and Golgi-to-ER retrograde transport. The polyclonal format preserves population-level genetic diversity, suitable for pooled screens and assays where clonal artifacts are undesirable.
HAP1 is a near-haploid human cell line originally derived from the KBM-7 chronic myeloid leukemia line. Its haploid karyotype facilitates genetic manipulation and phenotype interpretation, making it a preferred system for knockout studies and haploid genetic screens. The HAP1 background retains key features of leukemic cells, providing a relevant context for studying protein trafficking pathways implicated in cancer biology and drug responsiveness.
KDELR3 encodes a receptor that recognizes the C-terminal KDEL motif on ER-resident proteins that have escaped to the cis-Golgi, mediating their retrograde transport back to the ER via COPI-coated vesicles. This retrieval process is essential for maintaining ER proteostasis. KDELR3 functions downstream of ER stress sensors such as XBP1 and ATF6, which transcriptionally upregulate its expression during the unfolded protein response (UPR). It directly interacts with KDEL-containing client proteins, including the chaperone BiP/GRP78 and protein disulfide isomerase (PDI), as well as with COPI coat components like ??-COP and the small GTPase ARF1. KDELR3 cycles between the ER and Golgi through the ERGIC, cooperating with factors such as ERGIC-53, Sar1, and Rab6. Disruption of KDELR3 impairs retrieval of these clients, leading to ER stress and activation of downstream UPR targets, including Calreticulin and ERp57.
In the HAP1 background, KDELR3 knockout provides a powerful tool to dissect COPII-mediated anterograde and COPI-dependent retrograde transport pathways without the complexity of diploid genomes. The near-haploid nature ensures that gene disruption is effectively unmasked, facilitating clear genotype-phenotype correlations. This model is particularly valuable for studying ER stress, ER-associated degradation (ERAD), and the UPR, as well as their roles in cancer metastasis and drug resistance. Given the HAP1 cell’s origins from chronic myeloid leukemia, the knockout can be applied to investigate how ER proteostasis influences leukemic cell survival, proliferation, and sensitivity to chemotherapeutics.
Typical applications include monitoring ER stress responses via Western blotting for KDEL-bearing proteins, immunofluorescence co-localization with ER and Golgi markers, RT-qPCR for UPR target genes such as BiP and PDI, flow cytometry for ER stress sensors, and cell viability assays under ER stress. The polyclonal cell population is also suited for functional genomic screens and high-content imaging studies assessing protein trafficking dynamics. For additional information or technical support, please contact Ascent Research.
