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G protein-coupled receptors (GPCRs) are transmembrane protein receptors characterized by their interaction with a diverse array of ligands, including endogenous neurotransmitters and hormones, as well as exogenous natural and synthetic compounds. Upon binding to a receptor, agonists trigger the activation of signaling pathways; conversely, antagonists impede agonist-mediated receptor activation. Inverse agonists, in addition to interfering with agonists much like antagonists do, also suppress the constitutive activity of the receptor.

Glucose-dependent insulinotropic polypeptide (also known as gastric inhibitory polypeptide, GIP), glucagon-like peptide-1 (GLP-1), and glucagon (GCG) are peptide hormones responsible for maintaining glucose homeostasis. Their cognate receptors—GIPR, GLP-1R, and GCGR—belong to the Class B1 family of GPCRs. The gastric inhibitory polypeptide receptor (GIPR) serves as the receptor for GIP; it is a G protein-coupled receptor characterized by the presence of seven transmembrane domains. Upon binding to the GIP hormone, it enhances the synthesis and secretion of insulin by pancreatic beta cells in a glucose-dependent manner. GIPRs located on pancreatic beta cells play a pivotal role within the signaling cascade that ultimately leads to the release of insulin in response to elevated blood glucose levels.

The CHO-K1 Human GIPR Receptor Cell model effectively simulates the in vivo GIPR signal transduction process, the principle is illustrated in the figure below.

Figure 1. Schematic diagram of the CHO-K1 Human GIPR Receptor Cell model

Figure 2. HTRF CAMP Assay with GIPR CHO-K1( C12).

Figure 3. Inhibiton of GIP induced cAMP Level Change by GIPR Antagonist in GIPR CHO-K1( C12).

Cell Resuscitation
1)Rapidly thaw the frozen cells in a 37 °C water bath for approximately 60 seconds. Once thawed (which may take slightly less or more than 60 seconds), immediately transfer the cell suspension from the cryovial into a 15 mL centrifuge tube containing 10 mL of pre-warmed CHO-K1 Human GIPR Receptor Cell complete culture medium.
2)Centrifuge cells at 1000 rpm for 5 min to remove medium, then resuspend cells in 5 mL of pre-warmed complete medium.
3)Transfer the cell suspension into a T25 culture flask and incubate at 37 °C with 5% CO₂.
4)After approximately 24–36 hours, replace the medium or passage the cells to remove non-adherent dead cells.

Subculturing procedure
1)When the cell density reaches the appropriate confluency for passaging, wash the cells with PBS, then add 1 mL trypsin to detach the cells. When more than 80% of the cells detach upon gently tapping the culture flask, add complete culture medium to terminate digestion. Gently pipette to obtain a single-cell suspension, transfer to a 15 mL centrifuge tube, and centrifuge at 1000 rpm for 5 minutes.

2)Discard supernatant after centrifugation. Resuspend cells in fresh medium to a single-cell suspension and transfer to a new culture flask for continued growth.

Cell Freezing
After trypsinization and centrifugation of cells from each T75 flask or 10 cm culture dish, discard the supernatant. Add 2 mL of cryopreservation medium (90% FBS + 10% DMSO), gently resuspend thoroughly, and aliquot into two cryovials. Immediately place the cryovials into a controlled-rate freezing container (e.g., Nalgene 5100-0001), fill with isopropanol to the indicated level, and store at −80 °C. After 24 hours, transfer the cryovials to liquid nitrogen for long-term storage.