Pirt enhances TRPM8 sensitivity in response to menthol via PIP2 but not PI. (A) Representative inward current response to 1 mmol/L menthol in HEK293 cells stably expressing TRPM8 co-transfected with Pirt, where PIP2 (10 μmol/L) was added into the electrode pipette (Pirt+TRPM8+PIP2, n=12). (B) Representative inward current response to 1 mmol/L menthol in HEK293 cells stably expressing TRPM8 co-transfected with Pirt, where PI (10 μmol/L) was added into the electrode pipette (Pirt+TRPM8+PI, n=17). (C) Representative inward current response to 1 mmol/L menthol in HEK293 cells stably expressing TRPM8 without Pirt, where PIP2 (10 μmol/L) was added into electrode pipette (TRPM8+PIP2, n=13). (D) Representative inward current response to 1 mmol/L menthol in TRPM8 stably transfected HEK293 cells without Pirt, where the PI (10 μmol/L) was added into the electrode pipette (TRPM8+PI, n=12). (E) The current density among groups (A, B, C, and D) calculated from the current amplitude normalized to the cell capacitance was statistically compared. (F) The cell capacitance for four groups (A, B, C, and D) was statistically compared. The value is presented as the mean±SEM. cP<0.01, unpaired t-test. NS, non-significant difference.