The GRIPAP1 Knockout HAP1 Polyclonal Cells are a CRISPR/Cas9-induced heterogeneous knockout cell population targeting the GRIPAP1 (GRASP-1) gene. This polyclonal pool contains a spectrum of loss-of-function alleles in the HAP1 background, providing a robust loss-of-function model that avoids clonal artifacts. The polyclonal format is advantageous for downstream assays requiring population-averaged responses and minimizes the confounding effects of individual clone selection.
The HAP1 cell line is a human near-haploid chronic myeloid leukemia line derived from KBM-7 cells, originating from a male patient. Its near-haploid karyotype simplifies genetic manipulation and phenotypic interpretation, making it a popular model for haploid genetic screens and functional genomics. Despite its hematopoietic lineage, HAP1 cells have been broadly adopted to study fundamental cellular processes, including membrane trafficking and signal transduction.
GRIPAP1 acts as a Rab4-specific guanine nucleotide exchange factor (GEF) that is phosphorylated by CaMKII downstream of NMDA receptor activation. This phosphorylation stimulates Rab4-mediated recycling of AMPA receptors from early endosomes to the synaptic surface. GRIPAP1 achieves this by interacting with GluA1 and GluA2 subunits via the scaffolding proteins GRIP1 and GRIP2, and coordinates with Syntaxin 13 (STX13) at recycling endosomes. Thus, GRIPAP1 directly couples excitatory neurotransmission to the regulation of synaptic AMPA receptor levels and plasticity.
Although HAP1 cells are non-neuronal, they express core components of the endosomal recycling machinery, enabling the study of GRIPAP1’s GEF activity and its interactions with Rab4 and STX13 in a simplified system. The near-haploid nature of HAP1 cells reinforces the knockout phenotype, as only one allele requires disruption. This cell model is therefore highly suited for structure-function analyses, drug screens targeting endosomal trafficking, and genetic modifier screens uncovering regulators of AMPA receptor recycling relevant to neurodevelopmental disorders.
Typical applications include immunofluorescence to measure surface and total AMPA receptor levels, co-immunoprecipitation to assess GRIP?CGRIPAP1 complex formation, and Rab4 activation assays to quantify GEF activity. Western blotting for phospho-GRIPAP1 can validate CaMKII-dependent signaling, while endosomal trafficking assays track receptor recycling. The knockout cells are also compatible with high-throughput genetic and chemical screens. For further information or custom inquiries, please contact Ascent Research.
