Agonist-Induced Ca Signaling in HEK-293-Derived Cells Expressing a Single IP Receptor Isoform.

In mammals, three genes encode IP receptors (IPRs), which are involved in agonist-induced Ca signaling in cells of apparently all types. Using the CRISPR/Cas9 approach for disruption of two out of three IPR genes in HEK-293 cells, we generated three monoclonal cell lines, IP3R1-HEK, IP3R2-HEK, and IP3R3-HEK, with the single functional isoform, IPR1, IPR2, and IPR3, respectively. All engineered cells responded to ACh with Ca transients in an "all-or-nothing" manner, suggesting that each IPR isotype was capable of mediating CICR.