2.2. Cell culture and transfection

HEK293 cells were cultured in DMEM supplemented with 10% FBS, penicillin (100 U·ml⁻¹), and streptomycin (100 mg·ml⁻¹) for 24 to 48 hr at 37°C to reach 50% to 70% confluency. Transient transfection mediated by lipofectamine 2000 was conducted following the manufacturer's protocol. Calcium imaging and patch‐clamp recording were done 24 hr after transfection.