EC50: 10.5 μM (Ca ²⁺ current response from TPC2)

Two-pore channels (TPC1-3) are ancient members of the voltage-gated ion channel superfamily. TPCs are expressed throughout the endo-lysosomal system and regulates the trafficking of various cargoes. TPC2 can mediate different physiological and possibly pathophysiological effects depending on how it is activated.?The?ion selectivity of TPC2 is not fixed but rather agonist-dependent. TPC2 is a unique example of an ion channel that conducts different ions in response to different activating ligands.TPC2-A1-N (10 μM) reproducibly evokes Ca ²⁺ signals, and TPC2-A1-N response reachs its plateau faster than TPC2-A1-P. The EC ₅₀ in full concentration-effect relationships for the plateau response is 7.8 μM for TPC2-A1-N in a cell line stably expressing TPC2 ^L11A/L12A .TPC2-A1-N (10 μM) evokes Ca ²⁺ influx through the TPC2 pore evokes Ca ²⁺ signals in cells expressing TPC2L11A/L12A?but not TPC2 ^{L11A/L12A/L265P} . Additionally, the responses to TPC2-A1-N can be selectively blocked by the identified TPC2 blockers Tetrandrine (HY-13764, Tet), Raloxifene (HY-13738, Ral), and Fluphenazine (HY-A0081, Flu) by removal of extracellular Ca ²⁺ .In endo-lysosomal patch-clamp experiments, TPC2-A1-N (30 μM) elicits currents using Na ⁺ as the major permeantion, in vacuolin-enlarged endo-lysosomes isolated from isolated from HEK293 cells transiently expressing human TPC2 (hTPC2) but not in cells expressing TPC1.In endo-lysosomal patch-clamp experiments, TPC2-A1-N (30 μM) induces larger currents in endo-lysosomes isolated from cells expressing a gain-of-function variant of TPC2 (TPC2 ^M484L ) compared to the wild-type isoform, and exhibits an EC ₅₀ value of 0.6 μM for TPC2-A1-N.