The HSP90B1 Knockout HAP1 Polyclonal Cells represent a CRISPR/Cas9-edited polyclonal knockout population of HAP1 cells, carrying a targeted gene disruption of HSP90B1. This product provides a loss-of-function model for studying the ER-resident chaperone GRP94. As a mixed population of edited cells, it circumvents clonal selection bias and enables reproducible assessment of GRP94??s roles in protein folding, UPR signaling, and client protein maturation.
HAP1 is a near-haploid human cell line derived from a chronic myeloid leukemia (CML) patient, exhibiting a fibroblast-like morphology. Its haploid karyotype simplifies genetic manipulation and reveals loss-of-function phenotypes with high penetrance, making it a preferred platform for CRISPR/Cas9-based gene knockout experiments. The cells maintain relevant cancer and stress signaling pathways, providing a suitable context for interrogating HSP90B1 biology.
HSP90B1 encodes GRP94, an Hsp90 paralog molecular chaperone localized in the endoplasmic reticulum. GRP94 facilitates the folding of specific client proteins, including Toll-like receptors (TLR2, TLR4), integrins, LRP6, and IGF-IR. Under ER stress, upstream sensors IRE1??, PERK, and ATF6 activate transcription factors XBP1, ATF4, and HSF1 to coordinate the UPR. GRP94 interacts with BiP/GRP78, ERdj3, calreticulin, and components of the calnexin/calreticulin cycle. Knockout of HSP90B1 leads to misfolded protein accumulation, triggering UPR branches (IRE1??-XBP1 and PERK-ATF4-CHOP) and impairing MHC class I antigen presentation. Consequently, cell surface expression of TLRs and integrins is reduced, compromising innate immune signaling and adhesion.
In the HAP1 near-haploid background, HSP90B1 disruption yields a clear phenotype due to single-allele targeting, enhancing the sensitivity of functional assays. This model allows precise dissection of GRP94-dependent processes without interference from a second allele, facilitating studies of ER stress responses, chaperone network dynamics, and the impact on client protein trafficking. The polyclonal format is advantageous for population-level analyses such as drug screening, where heterogeneous responses better represent physiological variability.
Applications include functional investigation of ER chaperones, UPR signaling under genetic or pharmacological stress, and validation of HSP90B1 as a target in cancers like multiple myeloma and breast cancer. Representative assays include western blotting for GRP94, BiP, and CHOP; RT-qPCR for UPR target genes; immunofluorescence for ER stress markers; flow cytometry to quantify surface TLR and integrin levels; co-immunoprecipitation of chaperone-client complexes; and drug sensitivity assays with tunicamycin or thapsigargin. Apoptosis assays can assess downstream cell death pathways. For further details, contact Ascent Research.
